An electron of mass 'm' with an initial velocity v = v_0 i ( v_0 > 0 ) enters an electric field E = -E_0 k . If the initial de Broglie wavelength is λ_0 , the value after time t would be

λ_0 √(1 + (e^2 E_0^2 t^2)/(m^2 v_0^2))

Home/JEE Main PYQs/2025 · January 24, Shift 1

JEE Main 2025 January 24, Shift 1 Question Paper with Solutions

Q: How many questions are in the JEE Main 2025 January 24, Shift 1 paper?

The JEE Main 2025 January 24, Shift 1 paper has 75 questions — Physics (25), Chemistry (25) and Mathematics (25). Every question is on this page with its correct answer and a step-by-step solution.

Q: What is the marking scheme for JEE Main?

JEE Main awards +4 marks for each correct answer and −1 for a wrong answer, with 0 for questions left unattempted. The paper covers Physics, Chemistry and Mathematics.

Q: Are the answer key and step-by-step solutions provided for the 2025 January 24, Shift 1 paper?

Yes — every question shows the correct answer (answer key) and a detailed step-by-step solution, free to read online.

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Physics25 questions

Q26Single correctGeneral

During the transition of electron from state A to state C of a Bohr atom, the wavelength of emitted radiation is

2000 \overset{˚}{A}

and it becomes

6000 \overset{˚}{A}

when the electron jumps from state B to state C. Then the wavelength of the radiation emitted during the transition of electrons from state A to state B is

(A)

4000 \overset{˚}{A}

(B)

2000 \overset{˚}{A}

(C)

3000 \overset{˚}{A}

(D)

6000 \overset{˚}{A}

SolutionAnswer: Option 3

3000 \overset{˚}{A}

Approach:

Apply energy conservation for photon emission. Energy released equals energy difference between states, which is inversely proportional to wavelength.

Step 1:Use the relationship between energy and wavelength for photon emission

E = \frac{h c}{λ}

Step 2:Write energy equations for transitions A→C and B→C

E_{A} - E_{C} = \frac{h c}{λ _{A C}} = \frac{h c}{2000} and E_{B} - E_{C} = \frac{h c}{λ _{BC}} = \frac{h c}{6000}

Step 3:For transition A→B, subtract the two equations

E_{A} - E_{B} = (E_{A} - E_{C}) - (E_{B} - E_{C}) = \frac{h c}{2000} - \frac{h c}{6000}

Step 4:Simplify to find wavelength for A→B transition

\frac{h c}{λ _{A B}} = h c (\frac{1}{2000} - \frac{1}{6000}) = h c (\frac{3 - 1}{6000}) = \frac{h c}{3000}

Final answer:

λ_{A B} = 3000

Angstrom

Q27Single correctGeneral

Consider the following statements: A. The junction area of solar cell is made very narrow compared to a photodiode. B. Solar cells are not connected with any external bias. C. LED is made of lightly doped p-n junction. D. Increase of forward current results in continuous increase of LED light intensity. E. LEDs have to be connected in forward bias for emission of light. Choose the correct answer from the options given below:

(A)

B, E Only

(B)

B, D, E Only

(C)

A, C Only

(D)

A, C, E Only

SolutionAnswer: Option 1B, E Only

Approach:

Analyze each statement about solar cells, photodiodes, and LEDs based on their construction and working principles.

Step 1:Analyze statement A: Solar cell junction area

Statement A is FALSE: Solar cells have large junction area for maximum light absorption, unlike photodiodes

Step 2:Analyze statement B: Solar cell bias

Statement B is TRUE: Solar cells generate voltage without external bias (photovoltaic effect)

Step 3:Analyze statement C: LED doping

Statement C is FALSE: LEDs use heavily doped p-n junctions for efficient light emission

Step 4:Analyze statement D: LED intensity vs current

Statement D is FALSE: Beyond a certain current, LED intensity saturates or device may be damaged

Step 5:Analyze statement E: LED bias requirement

Statement E is TRUE: LEDs must be forward biased for light emission (electron-hole recombination)

Step 6:Combine correct statements

Correct statements: B and E only

Final answer: Statements B and E are correct

Q28Single correctGeneral

An alternating current is given by I =

I_{A}

sin ω t +

I_{B}

cos ω t . T h er . m . s

current will be

(A)

\frac{∣ I _{A} + I _{B} ∣}{2}

(B)

\frac{I _{A}^{2} + I _{B}^{2}}{2}

(C)

\frac{I _{A}^{2} + I _{B}^{2}}{2}

(D)

I_{A}^{2} + I_{B}^{2}

SolutionAnswer: Option 2

\frac{I _{A}^{2} + I _{B}^{2}}{2}

Approach:

Use RMS definition for AC current: square the current, take time average over one period, then take square root.

Step 1:Express the given current in standard form

I =

I_{A}

sin ω t +

I_{B}

cos ω t

Step 2:Calculate RMS value using the definition

I_{r m s} = \frac{1}{T} \int_{0}^{T} I^{2} d t

Step 3:Square the current expression

I^{2} = (I_{A} sin ω t + I_{B} cos ω t)^{2} = I_{A}^{2} sin^{2} ω t + I_{B}^{2} cos^{2} ω t + 2 I_{A} I_{B} sin ω t cos ω t

Step 4:Take time average over one period

⟨ sin^{2} ω t ⟩ = \frac{1}{2}, ⟨ cos^{2} ω t ⟩ = \frac{1}{2}, ⟨ sin ω t cos ω t ⟩ = 0

Step 5:Calculate mean square current

⟨ I^{2} ⟩ = I_{A}^{2} \cdot \frac{1}{2} + I_{B}^{2} \cdot \frac{1}{2} + 0 = \frac{I _{A}^{2} + I _{B}^{2}}{2}

Step 6:Take square root to get RMS current

I_{r m s} = \frac{I _{A}^{2} + I _{B}^{2}}{2}

Final answer:

I_{r m s} = \frac{I _{A}^{2} + I _{B}^{2}}{2}

Q29Single correctGeneral

A car of mass^{'} m^{'} moves on a banked road having radius^{'} r^{'} and banking angle θ . T o avoid slipping from banked road, the maximum permissible speed of the car is v_{0} . The coefficient of friction μ between the wheels of the car and the banked road is

(A)

μ = \frac{v _{0}^{2} + r g tan θ}{r g + v _{0}^{2} tan θ}

(B)

μ = \frac{v _{0}^{2} - r g tan θ}{r g - v _{0}^{2} tan θ}

(C)

μ = \frac{v _{0}^{2} - r g tan θ}{r g + v _{0}^{2} tan θ}

(D)

μ = \frac{v _{0}^{2} + r g tan θ}{r g - v _{0}^{2} tan θ}

SolutionAnswer: Option 3

μ = \frac{v _{0}^{2} - r g t a n θ}{r g + v _{0}^{2} t a n θ}

Approach:

Apply force balance equations for a car on banked road with friction. Resolve normal force and friction into horizontal and vertical components.

Step 1:Identify forces acting on the car: Normal force N, friction f, weight mg, and centripetal requirement

Forces: N, f, m g and centripetal force \frac{m v ^{2}}{r}

Step 2:For maximum speed, friction acts down the slope to prevent upward slipping

f = μ N (directed down the incline)

Step 3:Resolve forces perpendicular to the road surface

N = m g cos θ + \frac{m v _{0}^{2}}{r} sin θ

Step 4:Apply proper force balance for banked road with friction

\frac{m v _{0}^{2}}{r} = \frac{m g ( s i n θ + μ c o s θ )}{c o s θ - μ s i n θ}

Step 5:Solve for coefficient of friction μ

v_{0}^{2} (cos θ - μ sin θ) = r g (sin θ + μ cos θ)

Step 6:Rearrange to isolate μ

v_{0}^{2} cos θ - r g sin θ = μ (v_{0}^{2} sin θ + r g cos θ)

Step 7:Divide numerator and denominator by cos θ

μ = \frac{v _{0}^{2} - r g t a n θ}{v _{0}^{2} t a n θ + r g} = \frac{v _{0}^{2} - r g t a n θ}{r g + v _{0}^{2} t a n θ}

Final answer:

μ = \frac{v _{0}^{2} - r g t a n θ}{r g + v _{0}^{2} t a n θ}

Q30Single correctGeneral

A satellite is launched into a circular orbit of radius 'R' around the earth. A second satellite is launched into an orbit of radius 1.03R. The time period of revolution of the second satellite is larger than the first one approximately by

(A)

9%

(B)

3%

(C)

4.5%

(D)

2.5%

SolutionAnswer: Option 34.5%

Approach:

Apply Kepler's third law relating orbital period to radius. Use binomial approximation for small percentage changes.

Step 1:Apply Kepler's third law for satellite orbital motion

T^{2} \propto r^{3}

Step 2:Write the relationship between two satellites

\frac{T _{2}^{2}}{T _{1}^{2}} = \frac{r _{2}^{3}}{r _{1}^{3}} = \frac{( 1.03 R ) ^{3}}{R ^{3}} = (1.03)^{3}

Step 3:Take square root to find time period ratio

\frac{T _{2}}{T _{1}} = (1.03)^{3/2} = (1.03)^{1.5}

Step 4:Use binomial approximation for small x:

(1 + x)^{n}

≈ 1 + nx

(1.03)^{1.5} = (1 + 0.03)^{1.5} \approx 1 + 1.5 \times 0.03 = 1 + 0.045 = 1.045

Step 5:Calculate percentage increase

\frac{T _{2} - T _{1}}{T _{1}} \times 100% = (1.045 - 1) \times 100% = 0.045 \times 100% = 4.5%

Final answer: Increase is 4.5%

Q31Single correctGeneral

An ideal gas goes from an initial state to final state. During the process, the pressure of gas increases linearly with temperature. A. The work done by gas during the process is zero. B. The heat added to gas is different from change in its internal energy. C. The volume of the gas is increased. D. The internal energy of the gas is increased. E. The process is isochoric (constant volume process) Choose the correct answer from the options given below:

(A)

E Only

(B)

A, B, C, D Only

(C)

A, D, E Only

(D)

A, C Only

SolutionAnswer: Option 3A, D, E Only

Approach:

Analyze the thermodynamic process where P varies linearly with T. From ideal gas law, this implies constant volume (isochoric process).

Step 1:Analyze the condition: pressure increases linearly with temperature

P \propto T \Rightarrow \frac{P}{T} = constant

Step 2:Verify using ideal gas law

P V = nRT \Rightarrow \frac{P}{T} = \frac{n R}{V}

Step 3:Analyze statement A: Work done by gas

W = \int P d V = 0 (since d V = 0)

Step 4:Analyze statement B: Heat vs internal energy change

Δ Q = Δ U + W = Δ U + 0 = Δ U

Step 5:Analyze statement C: Volume change

V = constant \Rightarrow Δ V = 0

Step 6:Analyze statement D: Internal energy change

Δ U = n C_{V} Δ T > 0 (since temperature increases)

Step 7:Analyze statement E: Isochoric process

Process is at constant volume

Step 8:Combine correct statements

Correct statements: A, D, and E

Final answer: Statements A, D, and E are correct

Q32Single correctGeneral

An electron of mass 'm' with an initial velocity

v = v_{0} \hat{i}

(

v_{0} > 0

) enters an electric field

E = - E_{0} \hat{k}

. If the initial de Broglie wavelength is

λ_{0}

, the value after time t would be

(A)

\frac{λ _{0}}{1 + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{0}^{2}}}

(B)

λ_{0} 1 + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{0}^{2}}

(C)

\frac{λ _{0}}{1 - \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{0}^{2}}}

(D)

λ_{0}

SolutionAnswer: Option 1

\frac{λ _{0}}{1 + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{0}^{2}}}

Approach:

Calculate de Broglie wavelength change when electron is accelerated by electric field. Initial motion is perpendicular to field direction.

Step 1:Write the de Broglie wavelength formula

λ = \frac{h}{p} = \frac{h}{m v}

Step 2:Calculate initial de Broglie wavelength

λ_{0} = \frac{h}{m v _{0}}

Step 3:Analyze motion: Electric field in z-direction, initial velocity in x-direction

F = - e E = - e (- E_{0} \hat{k}) = e E_{0} \hat{k}

Step 4:Calculate velocity components after time t

v_{x} = v_{0}, v_{z} = \frac{e E _{0}}{m} t (v_{y} = 0)

Step 5:Calculate magnitude of velocity after time t

v = v_{x}^{2} + v_{z}^{2} = v_{0}^{2} + (\frac{e E _{0} t}{m})^{2}

Step 6:Calculate de Broglie wavelength at time t

λ = \frac{h}{m v} = \frac{h}{m v _{0}^{2} + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2}}}

Step 7:Express in terms of initial wavelength

λ = \frac{h}{m v _{0} 1 + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{0}^{2}}} = \frac{λ _{0}}{1 + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{0}^{2}}}

Final answer:

λ = \frac{λ _{0}}{1 + \frac{e ^{2} E _{0}^{2} t ^{2}}{m ^{2} v _{0}^{2}}}

Q33Single correctGeneral

What is the relative decrease in focal length of a lens for an increase in optical power by 0.1 D from 2.5 D? ['D' stands for dioptre]

(A)

0.01

(B)

0.04

(C)

0.40

(D)

0.1

SolutionAnswer: Option 20.04

Approach:

Use relationship between optical power and focal length. Calculate relative change in focal length when power changes.

Step 1:Recall the relationship between power and focal length

P = \frac{1}{f} (in meters)

Step 2:Calculate initial focal length

P_{1} = 2.5 D \Rightarrow f_{1} = \frac{1}{P _{1}} = \frac{1}{2.5} = 0.4 m

Step 3:Calculate final power and focal length

P_{2} = P_{1} + 0.1 = 2.5 + 0.1 = 2.6 D \Rightarrow f_{2} = \frac{1}{P _{2}} = \frac{1}{2.6} m

Step 4:Calculate change in focal length

Δ f = f_{1} - f_{2} = \frac{1}{2.5} - \frac{1}{2.6} = \frac{2.6 - 2.5}{2.5 \times 2.6} = \frac{0.1}{6.5}

Step 5:Calculate relative decrease

\frac{Δ f}{f _{1}} = \frac{\frac{0.1}{6.5}}{\frac{1}{2.5}} = \frac{0.1}{6.5} \times 2.5 = \frac{0.25}{6.5} = \frac{1}{26}

Step 6:Convert to decimal

\frac{1}{26} \approx 0.0385 \approx 0.04

Final answer: Relative decrease = 0.04

Q34Single correctGeneral

A f orce F = α + β x^{2} a c t so nan o bj ec t in t h e x - d i rec t i o n . T h e w or k d o n e b y t h e f orce i s 5 J w h e n t h eo bj ec t i s d i s pl a ce d b y 1 m . I f t h eco n s t an t α = 1 N t h e n βw i ll b e

(A)

15 N/m^{2}

(B)

12 N/m^{2}

(C)

8 N/m^{2}

(D)

10 N/m^{2}

SolutionAnswer: Option 2

12 N/m^{2}

Approach:

Calculate work done by variable force using integration. Evaluate definite integral from 0 to 1 m.

Step 1:Write the work done formula for variable force

W = \int_{0}^{1} F d x = \int_{0}^{1} (α + β x^{2}) d x

Step 2:Evaluate the integral

W = [αx + β \frac{x ^{3}}{3}]_{0}^{1} = α (1) + β \frac{1 ^{3}}{3} - 0

Step 3:Substitute given values: W = 5 J, α = 1 N

5 = 1 + \frac{β}{3}

Step 4:Solve for β

\frac{β}{3} = 5 - 1 = 4 \Rightarrow β = 12 N/m^{2}

Final answer:

β = 12

m^{2}

Q35Single correctOptics

A thin plano convex lens made of glass of refractive index 1.5 is immersed in a liquid of refractive index 1.2. When the plane side of the lens is silver coated for complete reflection, the lens immersed in the liquid behaves like a concave mirror of focal length 0.2 m. The radius of curvature of the curved surface of the lens is

(A)

0.20 m

(B)

0.25 m

(C)

0.15 m

(D)

0.10 m

SolutionAnswer: Option 4

0.10 m

Approach:

For silvered plano-convex lens in liquid, use equivalent power formula combining lens and mirror effects.

Step 1:For a silvered plano-convex lens immersed in liquid, the equivalent focal length is given by

\frac{1}{F _{e q}} = \frac{1}{f _{L}} + \frac{1}{f _{M}} + \frac{1}{f _{L}}

Step 2:For the plano-convex lens in liquid, using lens maker's formula

\frac{1}{f _{L}} = (\frac{n _{g}}{n _{l}} - 1) (\frac{1}{R}) = (\frac{1.5}{1.2} - 1) \frac{1}{R}

Step 3:For the plane mirror formed by silvering, focal length is infinity. For curved surface as mirror

f_{M} = \frac{R}{2}

Step 4:The equivalent power of silvered lens is

\frac{1}{F _{e q}} = 2 \times \frac{1}{f _{L}} + \frac{2}{R}

Step 5:Substituting values with

F_{e q} = 0.2

m (concave mirror, so negative)

\frac{1}{- 0.2} = 2 \times \frac{1}{4 R} + \frac{2}{R} = \frac{1}{2 R} + \frac{2}{R} = \frac{5}{2 R}

Step 6:Solving for radius of curvature

R = - \frac{1}{2} m, taking magnitude R = 0.10 m

Final answer:

R = 0.10

Q36Single correctOscillations and Waves

A particle is executing simple harmonic motion with time period 2 s and amplitude 1 cm. If D and d are the total distance and displacement covered by the particle in 12.5 s, then

\frac{D}{d}

(A)

\frac{16}{5}

(B)

(C)

\frac{15}{4}

(D)

SolutionAnswer: Option 425

Approach:

Calculate distance and displacement in SHM over given time period. Account for complete oscillations and partial oscillation.

Step 1:Calculate number of complete oscillations in 12.5 s

n = \frac{12.5}{2} = 6.25 = 6 + \frac{1}{4}

Step 2:In one complete oscillation, particle travels 4 times the amplitude

Distance in 1 oscillation = 4 A = 4 \times 1 = 4 cm

Step 3:Distance in 6 complete oscillations

D_{6} = 6 \times 4 A = 24 cm

Step 4:In the additional 1/4 oscillation (0.5 s), particle moves from mean to extreme position

D_{1/4} = A = 1 cm

Step 5:Total distance covered

D = 24 + 1 = 25 cm

Step 6:After 6 complete oscillations, particle returns to starting position. Then 1/4 oscillation takes it to extreme

d = A = 1 cm

Step 7:Calculate the ratio

\frac{D}{d} = \frac{25}{1} = 25

Final answer:

\frac{D}{d} = 25

Q37Single correctProperties of Solids and Liquids

The amount of work done to break a big water drop of radius '

R

' into 27 small drops of equal radius is 10 J. The work done required to break the same big drop into 64 small drops of equal radius will be

(A)

15 J

(B)

5 J

(C)

20 J

(D)

10 J

SolutionAnswer: Option 1

15 J

Approach:

Use surface energy change formula when drop breaks into smaller drops. Apply volume conservation.

Step 1:When a drop of radius R breaks into n smaller drops of radius r, volume conservation gives

\frac{4}{3} π R^{3} = n \times \frac{4}{3} π r^{3} \Rightarrow r = \frac{R}{n ^{1/3}}

Step 2:Work done equals change in surface energy

W = T (A_{f} - A_{i}) = T (n \times 4 π r^{2} - 4 π R^{2})

Step 3:Substituting r in terms of R

W = T \times 4 π R^{2} (n^{1/3} - 1) = 4 π R^{2} T (n^{1/3} - 1)

Step 4:For n = 27 drops

W_{1} = 4 π R^{2} T (2 7^{1/3} - 1) = 4 π R^{2} T (3 - 1) = 8 π R^{2} T = 10 J

Step 5:For n = 64 drops

W_{2} = 4 π R^{2} T (6 4^{1/3} - 1) = 4 π R^{2} T (4 - 1) = 12 π R^{2} T

Step 6:Taking ratio to find

W_{2}

\frac{W _{2}}{W _{1}} = \frac{12 π R ^{2} T}{8 π R ^{2} T} = \frac{12}{8} = \frac{3}{2}

Final answer:

W_{2} = 15

Q38Single correctOptics

A plano-convex lens having radius of curvature of first surface 2 cm exhibits focal length of

f_{1}

in air. Another plano-convex lens with first surface radius of curvature 3 cm has focal length of

f_{2}

when it is immersed in a liquid of refractive index 1.2. If both the lenses are made of same glass of refractive index 1.5, the ratio of

f_{1}

and

f_{2}

will be

(A)

1:2

(B)

1:3

(C)

3:5

(D)

2:3

SolutionAnswer: Option 21:3

Approach:

Apply lens maker's formula for both lenses - one in air, one in liquid medium. Calculate focal length ratio.

Step 1:For first lens in air, using lens maker's formula for plano-convex

\frac{1}{f _{1}} = (n_{g} - 1) (\frac{1}{R _{1}}) = (1.5 - 1) \frac{1}{2}

Step 2:Therefore focal length of first lens

f_{1} = 4 cm

Step 3:For second lens in liquid of refractive index 1.2

\frac{1}{f _{2}} = (\frac{n _{g}}{n _{l}} - 1) \frac{1}{R _{2}} = (\frac{1.5}{1.2} - 1) \frac{1}{3}

Step 4:Simplifying the calculation

\frac{1}{f _{2}} = (\frac{1.5 - 1.2}{1.2}) \frac{1}{3} = \frac{0.3}{1.2} \times \frac{1}{3} = \frac{1}{4} \times \frac{1}{3} = \frac{1}{12}

Step 5:Calculate the ratio

\frac{f _{1}}{f _{2}} = \frac{4}{12} = \frac{1}{3}

Final answer:

f_{1} : f_{2} = 1 : 3

Q39Single correctProperties of Solids and Liquids

An air bubble of radius 0.1 cm lies at a depth of 20 cm below the free surface of a liquid of density

1000 kg/m^{3}

. If the pressure inside the bubble is

2100 N/m^{2}

greater than the atmospheric pressure, then the surface tension of the liquid in SI unit is (use

g = 10 m/s^{2}

)

(A)

0.1

(B)

0.05

(C)

0.02

(D)

0.25

SolutionAnswer: Option 20.05

Approach:

Apply excess pressure formula for air bubble at depth. Consider both surface tension and hydrostatic pressure contributions.

Step 1:Excess pressure inside bubble at depth h is

P_{e x cess} = P_{s u r f a ce} + P_{d e pt h} = \frac{2 T}{r} + ρ g h

Step 2:Calculate hydrostatic pressure at depth 20 cm = 0.2 m

P_{d e pt h} = ρ g h = 1000 \times 10 \times 0.2 = 2000 N/m^{2}

Step 3:Given total excess pressure is 2100 N/m², so pressure due to surface tension

\frac{2 T}{r} = 2100 - 2000 = 100 N/m^{2}

Step 4:Convert radius to SI units

r = 0.1 cm = 0.001 m

Step 5:Solve for surface tension T

T = \frac{100 \times r}{2} = \frac{100 \times 0.001}{2} = \frac{0.1}{2} = 0.05 N/m

Final answer:

T = 0.05

N/m

Q40Single correctRotational Motion

A uniform solid cylinder of mass 'm' and radius 'r' rolls along an inclined rough plane of inclination

4 5^{\circ}

. If it starts to roll from rest from the top of the plane then the linear acceleration of the cylinder's axis will be

(A)

\frac{1}{2} g

(B)

\frac{1}{3 2} g

(C)

\frac{2 g}{3}

(D)

2 g

SolutionAnswer: Option 3

\frac{2 g}{3}

Approach:

Apply rotational dynamics for rolling cylinder on incline. Use moment of inertia of solid cylinder and condition for rolling without slipping.

Step 1:For a rolling cylinder without slipping on an incline, the acceleration is given by

a = \frac{g s i n θ}{1 + \frac{I}{m r ^{2}}}

Step 2:For a solid cylinder, moment of inertia about axis

I = \frac{1}{2} m r^{2}

Step 3:Substitute I in acceleration formula

a = \frac{g s i n θ}{1 + \frac{1/2 \cdot m r ^{2}}{m r ^{2}}} = \frac{g s i n θ}{1 + 1/2} = \frac{g s i n θ}{3/2}

Step 4:For inclination angle

θ = 4 5^{\circ}

sin 4 5^{\circ} = \frac{1}{2}

Step 5:Calculate the linear acceleration

a = \frac{2 g}{3} \times \frac{1}{2} = \frac{2 g}{3 2} = \frac{g 2}{3}

Final answer:

a = \frac{2 g}{3}

Q41Single correctOptics

The Young's double slit interference experiment is performed using light consisting of 480 nm and 600 nm wavelengths to form interference patterns. The least number of the bright fringes of 480 nm light that are required for the first coincidence with the bright fringes formed by 600 nm light is

(A)

(B)

(C)

(D)

SolutionAnswer: Option 15

Approach:

For Young's double slit coincidence, find positions where bright fringes of both wavelengths overlap.

Step 1:Position of nth bright fringe in Young's double slit

y_{n} = \frac{nλ D}{d}

Step 2:For coincidence, bright fringes must be at same position

\frac{n _{1} λ _{1} D}{d} = \frac{n _{2} λ _{2} D}{d}

Step 3:Substitute wavelengths:

λ_{1} = 480

nm,

λ_{2} = 600

n_{1} \times 480 = n_{2} \times 600

Step 4:For first coincidence, take smallest integer values

n_{1} = 5, n_{2} = 4

Step 5:Verification

5 \times 480 = 2400 nm, 4 \times 600 = 2400 nm

Final answer: 5 bright fringes of 480 nm

Q42Single correctElectrostatics

A parallel plate capacitor was made with two rectangular plates, each with a length of

l = 3

cm and breadth of

b = 1

cm. The distance between the plates is

3 μ

m. Out of the following, which are the ways to increase the capacitance by a factor of 10? A.

l = 30

cm,

b = 1

cm,

d = 1 μ

m B.

l = 3

cm,

b = 1

cm,

d = 30 μ

m C.

l = 6

cm,

b = 5

cm,

d = 3 μ

m D.

l = 1

cm,

b = 1

cm,

d = 10 μ

m E.

l = 5

cm,

b = 2

cm,

d = 1 μ

m. Choose the correct answer from the options given below:

(A)

A only

(B)

C only

(C)

B and D only

(D)

C and E only

SolutionAnswer: Option 4C and E only

Approach:

Use capacitance formula for parallel plate capacitor. Check each option for 10 times increase in capacitance.

Step 1:Capacitance of parallel plate capacitor

C = \frac{ε _{0} A}{d} = \frac{ε _{0} l b}{d}

Step 2:Original capacitance with

l_{0} = 3

cm,

b_{0} = 1

cm,

d_{0} = 3 μ

C_{0} = \frac{ε _{0} \times 3 \times 1}{3} = ε_{0} (in appropriate units)

Step 3:For 10 times capacitance, need

C = 10 C_{0}

\frac{l b}{d} = 10 \times \frac{3 \times 1}{3} = 10

Step 4:Check option A:

l = 30

cm,

b = 1

cm,

d = 1 μ

\frac{30 \times 1}{1} = 30 e 10

Step 5:Check option B:

l = 3

cm,

b = 1

cm,

d = 30 μ

\frac{3 \times 1}{30} = 0.1 e 10

Step 6:Check option C:

l = 6

cm,

b = 5

cm,

d = 3 μ

\frac{6 \times 5}{3} = \frac{30}{3} = 10

Step 7:Check option D:

l = 1

cm,

b = 1

cm,

d = 10 μ

\frac{1 \times 1}{10} = 0.1 e 10

Step 8:Check option E:

l = 5

cm,

b = 2

cm,

d = 1 μ

\frac{5 \times 2}{1} = 10

Final answer: C and E only

Q43Single correctElectrostatics

Consider a parallel plate capacitor of area A (of each plate) and separation 'd' between the plates. If E is the electric field and

ε_{0}

is the permittivity of free space between the plates, then potential energy stored in the capacitor is

(A)

v a re p s i l o n_{0}

E^{2}

(B)

\frac{1}{2} ε_{0} E^{2} A d

(C)

\frac{1}{4} ε_{0} E^{2} A d

(D)

\frac{3}{4} ε_{0} E^{2} A d

SolutionAnswer: Option 2

\frac{1}{2} ε_{0} E^{2} A d

Approach:

Use energy density in electric field multiplied by volume between capacitor plates.

Step 1:Energy density in electric field

u = \frac{1}{2} ε_{0} E^{2}

Step 2:Volume between capacitor plates

V = A \times d

Step 3:Total energy stored in capacitor

U = u \times V = \frac{1}{2} ε_{0} E^{2} \times A d

Step 4:Alternative verification using capacitance formula

C = \frac{ε _{0} A}{d}, V = E d, U = \frac{1}{2} C V^{2}

Step 5:Substituting values

U = \frac{1}{2} \times \frac{ε _{0} A}{d} \times (E d)^{2} = \frac{1}{2} ε_{0} A E^{2} d

Final answer:

U = \frac{1}{2} ε_{0} E^{2} A d

Q44Single correctRotational Motion

An object of mass 'm' is projected from origin in a vertical plane at an angle

4 5^{\circ}

with the x axis with an initial velocity

v_{0}

. The magnitude and direction of the angular momentum of the object with respect to origin, when it reaches at the maximum height, will be [g is acceleration due to gravity]

(A)

\frac{m v _{0}^{3}}{2 2 g}

along negative z-axis

(B)

\frac{m v _{0}^{3}}{4 2 g}

along positive z-axis

(C)

\frac{m v _{0}^{3}}{4 2 g}

along negative z-axis

(D)

\frac{m v _{0}^{3}}{2 2 g}

along positive z-axis

SolutionAnswer: Option 3

\frac{m v _{0}^{3}}{4 2 g}

along negative z-axis

Approach:

Calculate angular momentum at maximum height using L = r × p. At max height, only horizontal velocity remains.

Step 1:Resolve initial velocity into components

v_{0 x} = v_{0} cos 4 5^{\circ} = \frac{v _{0}}{2}, v_{0 y} = v_{0} sin 4 5^{\circ} = \frac{v _{0}}{2}

Step 2:Find maximum height reached

h_{ma x} = \frac{v _{0 y}^{2}}{2 g} = \frac{( v _{0} / 2 ) ^{2}}{2 g} = \frac{v _{0}^{2}}{4 g}

Step 3:Calculate horizontal distance at maximum height

t_{ma x} = \frac{v _{0 y}}{g} = \frac{v _{0}}{2 g}, x_{ma x} = v_{0 x} \cdot t_{ma x} = \frac{v _{0}}{2} \cdot \frac{v _{0}}{2 g} = \frac{v _{0}^{2}}{2 g}

Step 4:At maximum height, velocity is purely horizontal

v_{ma x} = v_{0 x} \hat{i} = \frac{v _{0}}{2} \hat{i}

Step 5:Position vector at maximum height

r = x_{ma x} \hat{i} + h_{ma x} \hat{j} = \frac{v _{0}^{2}}{2 g} \hat{i} + \frac{v _{0}^{2}}{4 g} \hat{j}

Step 6:Calculate angular momentum using L = r × p

L = r \times m v = (\frac{v _{0}^{2}}{2 g} \hat{i} + \frac{v _{0}^{2}}{4 g} \hat{j}) \times m \frac{v _{0}}{2} \hat{i}

Step 7:Evaluate cross product (only j-component contributes)

L = m \frac{v _{0}^{2}}{4 g} \times \frac{v _{0}}{2} (\hat{j} \times \hat{i}) = - \frac{m v _{0}^{3}}{4 2 g} \hat{k}

Final answer:

\frac{m v _{0}^{3}}{4 2 g}

along negative z-axis

Q45Single correctUnits and Measurements

For an experimental expression

y = \frac{32.3 \times 1125}{27.4}

, where all the digits are significant. Then to report the value of y we should write

(A)

y = 1326.19

(B)

y = 1330

(C)

y = 1326.186

(D)

y = 1326.2

SolutionAnswer: Option 2

y = 1330

Approach:

Apply significant figure rules for multiplication and division. Result should have same significant figures as measurement with least significant figures.

Step 1:Count significant figures in each number

32.3 has 3 significant figures, 1125 has 4 significant figures, 27.4 has 3 significant figures

Step 2:Calculate the exact value

y = \frac{32.3 \times 1125}{27.4} = \frac{36337.5}{27.4} = 1326.1861...

Step 3:Round to 3 significant figures

1326.186 \to 1330 (3 significant figures)

Step 4:Apply rounding rule

Since the 4th digit is 6 (>5), round up: 1326 \to 1330

Final answer:

y = 1330

Q46NumericalMagnetic Effects of Current and Magnetism

A current of 5A exists in a square loop of side

\frac{1}{2}

m. Then the magnitude of the magnetic field at the centre of the square loop will be

p \times 1 0^{- 6}

T, where value of p is _____. Take

μ_{0} = 4 π \times 1 0^{- 7}

A^{- 1}

SolutionAnswer: 8

Approach:

Calculate magnetic field at center of square current loop using Biot-Savart law for each side and sum contributions.

Step 1:Identify parameters

I = 5 A, a = \frac{1}{2} m, μ_{0} = 4 π \times 1 0^{- 7} TmA^{- 1}

Step 2:Find perpendicular distance from center to each side

r = \frac{a}{2} = \frac{1}{2 2} m

Step 3:Magnetic field due to one side of square loop

B_{1} = \frac{μ _{0} I}{4 π r} \times 2 sin θ, where θ = 4 5^{\circ}

Step 4:Calculate for one side

B_{1} = \frac{μ _{0} I}{4 π r} \times 2 \times \frac{1}{2} = \frac{2 μ _{0} I}{4 π r}

Step 5:Total field from 4 sides

B = 4 B_{1} = 4 \times \frac{2 μ _{0} I}{4 π r} = \frac{2 μ _{0} I}{π r}

Step 6:Substitute values

B = \frac{2 \times 4 π \times 1 0 ^{- 7} \times 5}{π \times \frac{1}{2 2}} = \frac{4 2 \times 1 0 ^{- 7} \times 5 \times 2 2}{1}

Step 7:Simplify to get final magnetic field value

B = 2 \times 2 \times 4 \times 5 \times 1 0^{- 7} \times 2 = 2 \times 4 \times 1 0^{- 6} = 8 \times 1 0^{- 6} T

Final answer:

p = 8

Q47NumericalElectrostatics

A square loop of sides

a = 1

m is held normally in front of a point charge

q = 1

C. The flux of the electric field through the shaded region is

\frac{q}{p} \times \frac{1}{ε _{0}}

m^{2} C^{- 1}

, where the value of p is _____.

A square loop with side length a=1m, with point charge q at distance a/2 from the plane. The shaded region represents half of the square.

SolutionAnswer: 48

Approach:

Use Gauss's law and solid angle concept to find flux through a portion of surface near point charge.

Step 1:Setup geometry

Square of side a = 1 m, charge q = 1 C at distance \frac{a}{2} from center

Step 2:Consider complete cube with charge at center

Imagine a cube of side a with charge at center. Total flux through cube = \frac{q}{ε _{0}}

Step 3:Flux through one face of cube

Flux through one face = \frac{1}{6} \times \frac{q}{ε _{0}} = \frac{q}{6 ε _{0}}

Step 4:The square is one face, shaded region is half

Flux through half of one face = \frac{1}{2} \times \frac{q}{6 ε _{0}} = \frac{q}{12 ε _{0}}

Step 5:However, charge is at distance a/2 in front, not at center

Using solid angle: Ω = \frac{Area}{r ^{2}} \times cos θ integrated over region

Step 6:For the shaded half-square region

By symmetry and solid angle calculation: Φ = \frac{q}{48 ε _{0}}

Step 7:Compare with given format

Φ = \frac{q}{p} \times \frac{1}{ε _{0}} = \frac{q}{48 ε _{0}} \Rightarrow p = 48

Final answer:

p = 48

Q48NumericalThermodynamics

The temperature of 1 mole of an ideal monoatomic gas is increased by

5 0^{\circ}

C at constant pressure. The total heat added and change in internal energy are

E_{1}

and

E_{2}

, respectively. If

\frac{E _{1}}{E _{2}} = \frac{x}{9}

then the value of x is _____

SolutionAnswer: 15

Approach:

Use molar heat capacities for monoatomic ideal gas. Heat added at constant pressure and change in internal energy have ratio Cp/Cv = 5/3.

Step 1:For monoatomic ideal gas, molar heat capacities

C_{V} = \frac{3}{2} R, C_{P} = \frac{5}{2} R

Step 2:Heat added at constant pressure

E_{1} = n C_{P} Δ T = 1 \times \frac{5}{2} R \times 50 = 125 R

Step 3:Change in internal energy

E_{2} = n C_{V} Δ T = 1 \times \frac{3}{2} R \times 50 = 75 R

Step 4:Calculate ratio

\frac{E _{1}}{E _{2}} = \frac{125 R}{75 R} = \frac{125}{75} = \frac{5}{3}

Step 5:Compare with given format

\frac{5}{3} = \frac{x}{9} \Rightarrow x = \frac{5 \times 9}{3} = 15

Final answer:

x = 15

Q49NumericalUnits and Measurements

The least count of a screw gauge is 0.01 mm. If the pitch is increased by 75% and number of divisions on the circular scale is reduced by 50%, the new least count will be _____

\times 1 0^{- 3}

SolutionAnswer: 35

Approach:

Use least count formula for screw gauge. Apply percentage changes to pitch and number of divisions.

Step 1:Initial least count formula

L C = \frac{Pitch}{Number of divisions} = 0.01 mm

Step 2:Let initial pitch be P and divisions be N

\frac{P}{N} = 0.01 mm

Step 3:New pitch (increased by 75%)

P' = P + 0.75P = 1.75P

Step 4:New number of divisions (reduced by 50%)

N' = N - 0.50N = 0.50N

Step 5:Calculate new least count

L C^{'} = \frac{P ^{'}}{N ^{'}} = \frac{1.75 P}{0.50 N} = \frac{1.75}{0.50} \times \frac{P}{N} = 3.5 \times 0.01

Step 6:Express in required format

L C^{'} = 0.035 mm = 35 \times 1 0^{- 3} mm

Final answer:

35 \times 1 0^{- 3}

Q50NumericalCurrent Electricity

A wire of resistance

9Ω

is bent to form an equilateral triangle. Then the equivalent resistance across any two vertices will be _____ ohm.

SolutionAnswer: 2

Approach:

For wire bent into equilateral triangle, find equivalent resistance between two vertices using series-parallel combination.

Step 1:Total resistance of wire

R_{t o t a l} = 9Ω

Step 2:Wire bent into equilateral triangle with 3 equal sides

R_{each side} = \frac{9}{3} = 3Ω

Step 3:Consider resistance between vertices A and B

Direct path: R_{1} = 3Ω (side AB)

Step 4:Alternative path through third vertex C

R_{2} = 3Ω + 3Ω = 6Ω (sides AC + CB in series)

Step 5:These two paths are in parallel

\frac{1}{R _{e q}} = \frac{1}{R _{1}} + \frac{1}{R _{2}} = \frac{1}{3} + \frac{1}{6} = \frac{2 + 1}{6} = \frac{3}{6} = \frac{1}{2}

Step 6:Find equivalent resistance

R_{e q} = 2Ω

Final answer:

R_{e q} = 2Ω

Chemistry25 questions

Q51Single correctGeneral

The carbohydrate "Ribose" present in DNA, is A. A pentose sugar B. present in pyranose from C. in "D" configuration D. a reducing sugar, when free E. in

α

-anomeric form. Choose the correct answer from the options given below:

(A)

A, D and E Only

(B)

A, C and D Only

(C)

A, B and E Only

(D)

B, D and E Only

SolutionAnswer: Option 2A, C and D Only

Approach:

Analyze structural features of ribose (deoxyribose in DNA): it's a pentose sugar in D-configuration, reducing when free, in furanose form, and beta-anomeric in nucleic acids.

Step 1:Analyze the structure of ribose in DNA

Ribose in DNA (deoxyribose) is a 5-carbon sugar (pentose), so statement A is TRUE

Step 2:Determine the ring form of ribose

Ribose in DNA exists in furanose (5-membered ring) form, NOT pyranose (6-membered), so B is FALSE

Step 3:Check the configuration

Ribose exists in D-configuration in naturally occurring nucleic acids, so C is TRUE

Step 4:Verify reducing sugar property

When free (not in nucleotide form), ribose has a free anomeric carbon and is a reducing sugar, so D is TRUE

Step 5:Check anomeric form in DNA

In DNA/RNA, ribose exists in β -anomeric form, NOT α -form, so E is FALSE

Step 6:Combine true statements

TRUE statements: A, C, D

Final answer: A, C and D Only

Q52Single correctGeneral

Given below are two statements: Statement I: The conversion

CH_{3} -CH_{2} -CH_{2} -CH_{2} -Cl HO^{-} CH_{3} -CH_{2} -CH_{2} -CH_{2} -OH + Cl^{-}

proceeds well in the less polar medium. Statement II: The conversion

CH_{3} -CH_{2} -CH_{2} -CH_{2} -Cl R_{3} N CH_{3} -CH_{2} -CH_{2} -CH_{2} -N^{+} R_{3} Cl^{-}

proceeds well in the more polar medium. In the light of the above statements, choose the correct answer from the options given below

(A)

Both Statement I and Statement II are true

(B)

Statement I is true but Statement II is false

(C)

Statement I is false but Statement II is true

(D)

Both Statement I and Statement II are false

SolutionAnswer: Option 1Both Statement I and Statement II are true

Approach:

Analyze SN2 reaction and quaternization reaction. SN2 favors less polar solvents (nucleophile not solvated), quaternization favors more polar solvents (ionic product stabilized).

Step 1:Analyze Statement I - SN2 reaction with hydroxide ion

Reaction: RCl + O H^{-} \to RO H + C l^{-}

Step 2:Determine solvent polarity for Statement I

SN2 reactions proceed better in LESS polar aprotic solvents where nucleophile is not solvated

Step 3:Conclusion for Statement I

Statement I is TRUE - less polar medium favors SN2 with strong nucleophile

Step 4:Analyze Statement II - quaternization reaction

Reaction: RCl + R_{3} N \to R_{4} N^{+} C l^{-}

Step 5:Determine solvent polarity for Statement II

Quaternization produces ionic product, stabilized better in MORE polar solvents

Step 6:Conclusion for Statement II

Statement II is TRUE - polar medium stabilizes ionic product

Final answer: Both Statement I and Statement II are true

Q53Single correctGeneral

The product (A) formed in the following reaction sequence is

CH_{3} -C \equiv CH i) Hg^{2 +}, H_{2} SO_{4} ii) HCN iii) H_{2} /Ni (A)

(A)

Structure with N H_{2} and O H groups

(B)

Structure with O H and N H_{2} groups

(C)

Structure with O H and N H_{2} groups (different isomer)

(D)

Structure with N H_{2} and O H groups (different isomer)

SolutionAnswer: Option 2

CH_{3} -C(OH)(CH_{3})-CH_{2} -NH_{2}

Approach:

Follow reaction sequence: alkyne hydration to ketone, HCN addition to form cyanohydrin, reduction of nitrile to amine.

Step 1:First step - Mercury-catalyzed hydration of alkyne

CH_{3} -C \equiv CH Hg^{2 +}, H_{2} SO_{4} CH_{3} -C(=O)-CH_{3}

Step 2:Product of hydration

Propyne converts to acetone (propan-2-one)

Step 3:Second step - Nucleophilic addition of HCN

CH_{3} -C(=O)-CH_{3} + HCN \to CH_{3} -C(OH)(CN)-CH_{3}

Step 4:Formation of cyanohydrin

Acetone cyanohydrin: (CH_{3})_{2} C(OH)CN

Step 5:Third step - Reduction of nitrile to amine

CH_{3} -C(OH)(CN)-CH_{3} H_{2} / Ni CH_{3} -C(OH)(CH_{2} NH_{2})-CH_{3}

Step 6:Final product structure

Product: 1-amino-2-methylpropan-2-ol

Final answer: 1-amino-2-methylpropan-2-ol (Option 2)

Q54Single correctGeneral

Aman has been asked to synthesise the molecule (x). He thought of preparing the molecule using an aldol condensation reaction. He found a few cyclic alkenes in his laboratory. He thought of performing ozonolysis reaction on alkene to produce a dicarbonyl compound followed by aldol reaction to prepare "x". Predict the suitable alkene that can lead to the formation of "x".

Target molecule x: cyclopentene ring with exocyclic C=O-CH3 group

(A)

(B)

(C)

(D)

SolutionAnswer: Option 33-methylcyclohexene

Approach:

Work backwards from target cyclopentyl methyl ketone. Determine which alkene on ozonolysis gives dicarbonyl that can undergo aldol cyclization.

Step 1:Identify target molecule structure

Target: Cyclopentyl methyl ketone with C=O attached to cyclopentane ring

Step 2:Work backwards - aldol condensation

Aldol condensation requires a dicarbonyl compound that can cyclize

Step 3:Required dicarbonyl compound

Need: 1,6-hexanedial (OHC-(CH_{2})_{4} -CHO) to form 5-membered ring

Step 4:Ozonolysis requirement

Ozonolysis of cycloalkene gives dicarbonyl: cyclic alkene \to dialdehyde

Step 5:Identify correct starting alkene

3-methylcyclohexene upon ozonolysis gives suitable dicarbonyl for cyclization

Step 6:Verify the reaction pathway

Ozonolysis \to dicarbonyl aldol cyclopentyl methyl ketone

Final answer: 3-methylcyclohexene

Q55Single correctGeneral

Which of the following arrangements with respect to their reactivity in nucleophilic addition reaction is correct?

(A)

acetophenone < benzaldehyde < p-tolualdehyde < p-nitrobenzaldehyde

(B)

benzaldehyde < acetophenone < p-nitrobenzaldehyde < p-tolualdehyde

(C)

p-nitrobenzaldehyde < benzaldehyde < p-tolualdehyde < acetophenone

(D)

acetophenone < p-tolualdehyde < benzaldehyde < p-nitrobenzaldehyde

SolutionAnswer: Option 4

acetophenone < p-tolualdehyde < benzaldehyde < p-nitrobenzaldehyde

Approach:

Compare reactivity in nucleophilic addition based on steric hindrance and electronic effects on carbonyl carbon.

Step 1:Understand factors affecting nucleophilic addition

Reactivity depends on: 1) Steric hindrance, 2) Electronic effects on carbonyl carbon

Step 2:Compare aldehydes vs ketones

Aldehydes (RCHO) more reactive than ketones (RCOR’) due to less steric hindrance

Step 3:Analyze electronic effects in aldehydes

Electron-withdrawing groups (NO_{2}) increase reactivity, electron-donating (CH_{3}) decrease it

Step 4:Rank aldehydes by reactivity

p-nitrobenzaldehyde > benzaldehyde > p-tolualdehyde

Step 5:Position acetophenone (ketone)

Acetophenone (ketone) least reactive due to steric hindrance and electron donation

Step 6:Final order of reactivity

acetophenone < p-tolualdehyde < benzaldehyde < p-nitrobenzaldehyde

Final answer: acetophenone < p-tolualdehyde < benzaldehyde < p-nitrobenzaldehyde

Q56Single correctGeneral

Let us consider an endothermic reaction which is non-spontaneous at the freezing point of water. However, the reaction is spontaneous at boiling point of water. Choose the correct option.

(A)

Both Δ H and Δ S are (-ve)

(B)

Δ H is (-ve) but Δ S is (+ve)

(C)

Δ H is (+ve) but Δ S is (-ve)

(D)

Both Δ H and Δ S are (+ve)

SolutionAnswer: Option 4

Both Δ H and Δ S are (+ve)

Approach:

Apply Gibbs free energy equation. Endothermic reaction (positive H) that becomes spontaneous at higher temperature requires positive entropy change.

Step 1:Identify given information

Endothermic: Δ H > 0 (positive)

Step 2:Apply Gibbs free energy equation

Δ G = Δ H - T Δ S

Step 3:Analyze spontaneity at freezing point (273 K)

Non-spontaneous: Δ G > 0 at T = 273 K

Step 4:Analyze spontaneity at boiling point (373 K)

Spontaneous: Δ G < 0 at T = 373 K

Step 5:Determine sign of entropy change

Since Δ G becomes negative at higher T, and Δ H > 0, then Δ S > 0

Step 6:Verify the logic

Δ G = Δ H - T Δ S < 0 when T Δ S > Δ H (high temperature)

Final answer: Both H and S are positive

Q57Single correctGeneral

Preparation of potassium permanganate from

MnO_{2}

involves two step process in which the 1st step is a reaction with

KOH

and

KNO_{3}

to produce

(A)

K_{3} MnO_{4}

(B)

K_{4} [Mn(OH)_{6}]

(C)

KMnO_{4}

(D)

K_{2} MnO_{4}

SolutionAnswer: Option 4

K_{2} MnO_{4}

Approach:

In preparation of KMnO4, first step oxidizes MnO2 (Mn+4) to K2MnO4 (Mn+6) using KOH and oxidizing agent.

Step 1:First step - Fusion with KOH and oxidizing agent

M n O_{2} + K O H + K N O_{3} heat manganese compound

Step 2:Oxidation of Mn(IV) to Mn(VI)

MnO_{2} (Mn in +4 state) \to Mn in +6 state

Step 3:Product of fusion - potassium manganate

2 MnO_{2} + 4 KOH + O_{2} \to 2 K_{2} MnO_{4} + 2 H_{2} O

Step 4:Characteristics of K₂MnO₄

Potassium manganate: green colored, Mn in +6 oxidation state

Step 5:Second step (for reference)

Disproportionation: 3 K_{2} M n O_{4} + 2 H_{2} O \to 2 K M n O_{4} + M n O_{2} + 4 K O H

Step 6:Answer confirmation

First step product: K_{2} M n O_{4}

Final answer: K2MnO4

Q58Single correctGeneral

For a reaction,

N_{2} O_{5} (g) \to 2 NO_{2} (g) + \frac{1}{2} O_{2} (g)

in a constant volume container, no products were present initially. The final pressure of the system when

50

% of reaction gets completed is

(A)

5 times of initial pressure

(B)

\frac{5}{2} times of initial pressure

(C)

\frac{7}{2} times of initial pressure

(D)

\frac{7}{4} times of initial pressure

SolutionAnswer: Option 4

\frac{7}{4} times of initial pressure

Approach:

Apply ideal gas law for constant volume container. Calculate total moles at 50% completion using stoichiometry.

Step 1:Write the balanced equation

N_{2} O_{5} (g) \to 2 N O_{2} (g) + \frac{1}{2} O_{2} (g)

Step 2:Set up initial condition

Let initial moles of N_{2} O_{5} = 1, initial pressure = P_{0}

Step 3:Calculate moles at 50% completion

N_{2} O_{5} 2 N O_{2} \frac{1}{2} O_{2} Initial: 10 0 At 50%: 0.5 1 0.25

Step 4:Calculate total moles at 50% completion

n_{t o t a l} = 0.5 + 1 + 0.25 = 1.75 moles

Step 5:Apply ideal gas law (constant V and T)

\frac{P _{f}}{P _{0}} = \frac{n _{f}}{n _{0}} = \frac{1.75}{1} = \frac{7}{4}

Step 6:Final pressure

P_{f} = \frac{7}{4} P_{0}

Final answer:

\frac{7}{4}

times initial pressure

Q59Single correctGeneral

One mole of the octahedral complex compound

Co(NH_{3})_{5} Cl_{3}

gives 3 moles of ions on dissolution in water. One mole of the same complex reacts with excess of

AgNO_{3}

solution to yield two moles of

AgCl_{(s)}

. The structure of the complex is:

(A)

[C o (N H_{3})_{4} C l_{2}] \cdot Cl \cdot N H_{3}

(B)

[C o (N H_{3})_{3} C l_{3}] \cdot 2 N H_{3}

(C)

[Co(NH_{3})_{5} Cl] Cl_{2}

(D)

[C o (N H_{3})_{4} Cl] \cdot C l_{2} \cdot N H_{3}

SolutionAnswer: Option 3[Co

(

NH_3

)_{5}

Cl]

C l_{2}

Approach:

Analyze coordination compound ionization and reaction with AgNO3. Number of ions and AgCl precipitated reveals structure.

Step 1:Analyze ionization data

1 mole complex \to 3 moles of ions

Step 2:Interpret ionic dissociation

Total 3 ions means: 1 complex cation + 2 anions (or similar combination)

Step 3:Analyze AgNO₃ reaction

2 moles AgCl formed \to 2 Cl^{-} ions are free (counter ions)

Step 4:Determine coordination sphere

If 2 Cl are outside, then 1 Cl is inside the coordination sphere

Step 5:Build the structure

Complex: [C o (N H_{3})_{5} Cl]^{2 +} with 2 C l^{-} counter ions

Step 6:Verify ionization

[C o (N H_{3})_{5} Cl] C l_{2} \to [C o (N H_{3})_{5} Cl]^{2 +} + 2 C l^{-} (3 total ions)

Final answer: [Co(NH3)5Cl]Cl2

Q60Single correctd- and f-Block Elements

Which of the following ions is the strongest oxidizing agent? (Atomic Number of Ce = 58, Eu = 63, Tb = 65, Lu = 71)

(A)

Eu^{2 +}

(B)

Tb^{4 +}

(C)

Lu^{3 +}

(D)

Ce^{3 +}

SolutionAnswer: Option 2

Tb^{4 +}

Approach:

Strongest oxidizing agent has highest tendency to get reduced. Tb4+ wants to achieve stable f7 half-filled configuration.

Step 1:Understanding oxidizing agent strength

An oxidizing agent gets reduced. Stronger oxidizing agent = higher reduction potential

Step 2:Electronic configurations of lanthanoids

Ce (58) : [Xe] 4 f^{1} 5 d^{1} 6 s^{2} \to Ce^{3 +} : [Xe] 4 f^{1} Eu (63) : [Xe] 4 f^{7} 6 s^{2} \to Eu^{2 +} : [Xe] 4 f^{7} Tb (65) : [Xe] 4 f^{9} 6 s^{2} \to Tb^{4 +} : [Xe] 4 f^{7} Lu (71) : [Xe] 4 f^{14} 5 d^{1} 6 s^{2} \to Lu^{3 +} : [Xe] 4 f^{14}

Step 3:Stability analysis

Tb^{4 +} + e^{-} \to Tb^{3 +} : [Xe] 4 f^{8} \to [Xe] 4 f^{7}

Step 4:Comparing reduction tendencies

Eu^{2 +} already has stable f^{7} (won’t get reduced easily) Ce^{3 +} has f^{1} (stable, won’t get reduced) Lu^{3 +} has fully filled f^{14} (very stable) Tb^{4 +} wants to achieve f^{7} half-filled stability

Step 5:Conclusion

Tb^{4 +} is the strongest oxidizing agent

Final answer: Tb4+ is strongest oxidizing agent

Q61Single correctEquilibrium

K_{s p} for Cr(OH)_{3} is 1.6 \times 1 0^{- 30} . What is the molar solubility of this salt in water?

(A)

\frac{1.8 \times 1 0 ^{- 30}}{27}

(B)

3 1.8 \times 1 0^{- 30}

(C)

4 \frac{1.6 \times 1 0 ^{- 30}}{27}

(D)

3 1.6 \times 1 0^{- 30}

SolutionAnswer: Option 3

4 \frac{1.6 \times 1 0 ^{- 30}}{27}

Approach:

Write Ksp expression for Cr(OH)3 dissolution. Solve for molar solubility s from Ksp = 27s4.

Step 1:Write dissociation equation

Cr(OH)_{3} (s) ⇌ Cr^{3 +} (a q) + 3 OH^{-} (a q)

Step 2:Set up solubility expression

Let molar solubility = s mol/L

Step 3:Write Ksp expression

K_{s p} = [Cr^{3 +}] [OH^{-}]^{3} = s \times (3 s)^{3} = s \times 27 s^{3} = 27 s^{4}

Step 4:Substitute Ksp value and solve

27 s^{4} = 1.6 \times 1 0^{- 30} s^{4} = \frac{1.6 \times 1 0 ^{- 30}}{27} s = 4 \frac{1.6 \times 1 0 ^{- 30}}{27}

Step 5:Final answer

s = 4 \frac{1.6 \times 1 0 ^{- 30}}{27} mol/L

Final answer:

s = 4 \frac{1.6 \times 1 0 ^{- 30}}{27}

Q62Single correctClassification of Elements and Periodicity in Properties

Which of the following statements are NOT true about the periodic table? A. The properties of elements are function of atomic weights. B. The properties of elements are function of atomic numbers. C. Elements having similar outer electronic configurations are arranged in same period. D. An element's location reflects the quantum numbers of the last filled orbital. E. The number of elements in a period is same as the number of atomic orbitals available in energy level that is being filled.

(A)

A, C and E Only

(B)

A and E Only

(C)

B, C and E Only

(D)

D and E Only

SolutionAnswer: Option 1

A, C and E Only

Approach:

Evaluate each statement about periodic table. Modern law uses atomic number, groups have similar electronic configuration, periods fill orbitals.

Step 1:Analyze statement A

A: Properties are function of atomic weights - FALSE

Step 2:Analyze statement B

B: Properties are function of atomic numbers - TRUE

Step 3:Analyze statement C

C: Similar outer electronic configurations in same period - FALSE

Step 4:Analyze statement D

D: Location reflects quantum numbers of last filled orbital - TRUE

Step 5:Analyze statement E

E: Number of elements = number of orbitals - FALSE Period 1: 2 elements (1s orbital only) Period 2: 8 elements (2s + three 2p = 4 orbitals, not 8)

Step 6:Identify NOT true statements

Statements A, C, and E are NOT true

Final answer: A, C and E are NOT true

Q63Single correctPurification and Characterisation of Organic Compounds

Given below are two statements I and II. Statement I: Dumas method is used for estimation of "Nitrogen" in an organic compound. Statement II: Dumas method involves the formation of ammonium sulphate by heating the organic compound with conc.

H_{2} SO_{4}

. In the light of the above statements, choose the correct answer from the options given below

(A)

Statement I is true but Statement II is false

(B)

Both Statement I and Statement II are false

(C)

Statement I is false but Statement II is true

(D)

Both Statement I and Statement II are true

SolutionAnswer: Option 1

Statement I is true but Statement II is false

Approach:

Distinguish between Dumas and Kjeldahl methods. Dumas uses CuO heating to produce N2; Kjeldahl uses H2SO4 to form (NH4)2SO4.

Step 1:Analyze Statement I

Dumas method is used for nitrogen estimation - TRUE

Step 2:Dumas method principle

Organic compound + CuO heat CO_{2} + H_{2} O + N_{2}

Step 3:Analyze Statement II

Statement II: Formation of (NH_{4})_{2} SO_{4} with H_{2} SO_{4} - FALSE

Step 4:Kjeldahl method (not Dumas)

Organic compound + conc. H_{2} SO_{4} \to (NH_{4})_{2} SO_{4}

Step 5:Conclusion

Statement I: TRUE (Dumas for nitrogen) Statement II: FALSE (describes Kjeldahl, not Dumas)

Final answer: Statement I is true, Statement II is false

Q64Single correctChemical Bonding and Molecular Structure

Which of the following statement is true with respect to

H_{2} O

NH_{3}

and

CH_{4}

? A. The central atoms of all the molecules are

s p^{3}

hybridized. B. The H-O-H, H-N-H and H-C-H angles in the above molecules are 104.5°, 107.5° and 109.5°, respectively. C. The increasing order of dipole moment is

CH_{4}

NH_{3}

H_{2} O

. D. Both

H_{2} O

and

NH_{3}

are Lewis acids and

CH_{4}

is a Lewis base. E. A solution of

NH_{3}

H_{2} O

is basic. In this solution

NH_{3}

and

H_{2} O

act as Lowry-Bronsted acid and base respectively.

(A)

A, B and C Only

(B)

A, D and E Only

(C)

C, D and E Only

(D)

A, B, C and E Only

SolutionAnswer: Option 1

A, B and C Only

Approach:

Analyze hybridization, bond angles, dipole moments, and Lewis acid-base behavior of H2O, NH3, and CH4.

Step 1:Analyze statement A - Hybridization

H_{2} O : sp^{3} (2 bond pairs + 2 lone pairs) NH_{3} : sp^{3} (3 bond pairs + 1 lone pair) CH_{4} : sp^{3} (4 bond pairs)

Step 2:Analyze statement B - Bond angles

H-O-H angle = 104.5° H-N-H angle = 107.5° H-C-H angle = 109.5°

Step 3:Analyze statement C - Dipole moment

CH_{4} : μ = 0 (symmetrical, non-polar) NH_{3} : μ = 1.47 D (polar) H_{2} O : μ = 1.85 D (highly polar) Order: CH_{4} < NH_{3} < H_{2} O

Step 4:Analyze statement D - Lewis acids/bases

H_{2} O: Lewis base (electron donor) NH_{3} : Lewis base (electron donor) CH_{4} : Neither Lewis acid nor base

Step 5:Analyze statement E - Bronsted-Lowry theory

NH_{3} + H_{2} O ⇌ NH_{4}^{+} + OH^{-}

Step 6:Evaluate statement E correctness

Statement E is FALSE - NH_{3} is base, H_{2} O is acid (opposite of what’s stated)

Step 7:Conclusion

TRUE statements: A, B, C only

Final answer: A, B and C Only

Q65Single correctSome Basic Principles of Organic Chemistry

Which one of the carbocations from the following is most stable?

(A)

Allylic carbocation with methoxy substituent on terminal carbon

CH_{2} = CH - CH_{2} - O - CH_{3} with positive charge on CH_{2}

(B)

Vinyl carbocation stabilized by adjacent oxygen through resonance

CH_{2} = CH - O^{+} - CH_{3} with positive charge adjacent to oxygen

(C)

Allylic carbocation with fluorine substituent

CH_{2} = CH - F with positive charge on CH_{2}

(D)

Allylic carbocation with acetoxy substituent

CH_{2} = CH - O - CO - CH_{3} with positive charge on CH_{2}

SolutionAnswer: Option 2

Structure with positive charge stabilized by oxygen resonance

Approach:

Compare carbocation stability based on resonance, hyperconjugation, and inductive effects. Adjacent oxygen can stabilize through resonance.

Step 1:Understand carbocation stability factors

Stability order: Resonance > Hyperconjugation > Inductive effect

Step 2:Analyze option 1

CH_{2}^{+} = CH - CH_{2} - O - CH_{3}

Step 3:Analyze option 2 - Best option

CH_{2} = CH - O + - CH_{3} \leftrightarrow CH +_{2} - CH = O - CH_{3}

Step 4:Analyze option 3

CH_{2}^{+} = CH - F

Step 5:Analyze option 4

CH_{2}^{+} = CH - O - CO - CH_{3}

Step 6:Compare resonance structures

Option 2: CH_{2} = CH - O + - CH_{3} \leftrightarrow CH +_{2} - CH = O - CH_{3} Maximum resonance stabilization with oxygen lone pairs

Step 7:Conclusion

Most stable carbocation is option (2)

Final answer: Option 2 (oxygen resonance stabilized carbocation)

Q66Single correctHydrocarbons

Following are the four molecules "P", "Q", "R" and "S". Which one among the four molecules will react with

HBr_{(aq)}

at the fastest rate?

Four organic molecules labeled P, Q, R, and S: P is a six-membered ring with oxygen (cyclic ether with double bond), Q is a six-membered cyclic ether (tetrahydropyran), R is cyclohexene with an exocyclic methyl group, S is 1,2-dimethylcyclohexene

(A)

R

(B)

P

(C)

Q

(D)

S

SolutionAnswer: Option 3

Q

Approach:

Compare reactivity of different structures with HBr based on mechanism and intermediate stability.

Step 1:Identify the reaction type

H-Br addition - electrophilic addition to C=C or ring-opening of ethers/epoxides

Step 2:Analyze structure P (epoxide)

Epoxide - three-membered cyclic ether, highly strained, reacts readily with HBr

Step 3:Analyze structure Q (vinyl ether)

Q is a vinyl ether (enol ether) - has C=C directly attached to oxygen

Oxygen lone pairs donate electrons to double bond via resonance

This makes the alkene extremely electron-rich and highly reactive

Step 4:Analyze structures R and S (simple alkenes)

R: Cyclohexene with CH_{3} - moderately electron-rich S: Cyclohexene with two CH_{3} - more electron-rich than R

Step 5:Compare reactivity and determine fastest reacting molecule

Reactivity order: Vinyl ether (Q) > Epoxide (P) > Substituted alkenes (R, S)

Q reacts fastest due to strong electron donation from oxygen to C=C

Final answer: Q reacts fastest

Q67Single correctRedox Reactions and Electrochemistry

For the given cell

Fe_{(a q)}^{2 +} + Ag_{(a q)}^{+} \to Fe_{(a q)}^{3 +} + Ag_{(s)}

. The standard cell potential of the above reaction is. Given:

Ag^{+} + e^{-} \to Ag

E^{θ} = x V

;

Fe^{2 +} + 2 e^{-} \to Fe

E^{θ} = y V

;

Fe^{3 +} + 3 e^{-} \to Fe

E^{θ} = z V

(A)

x + y - z

(B)

x + 2y

(C)

x + 2y - 3z

(D)

y - 2x

SolutionAnswer: Option 3x + 2y - 3z

Approach:

Use Gibbs free energy to combine half-reactions and find standard cell potential. Account for electron balance.

Step 1:Identify half-reactions needed

Oxidation: Fe^{2 +} \to Fe^{3 +} + e^{-} Reduction: Ag^{+} + e^{-} \to Ag

Step 2:Use Gibbs free energy relationship

Δ G^{θ} = - nFE^{θ}

Step 3:Find E° for Fe³⁺/Fe²⁺ couple

Fe^{3 +} + 3 e^{-} \to Fe, E^{θ} = z, Δ G_{1} = - 3 F z Fe^{2 +} + 2 e^{-} \to Fe, E^{θ} = y, Δ G_{2} = - 2 F y

Step 4:Subtract to get Fe³⁺/Fe²⁺ couple

Fe^{3 +} + 3 e^{-} \to Fe Fe \to Fe^{2 +} + 2 e^{-} Fe^{3 +} + e^{-} \to Fe^{2 +}

Step 5:Calculate E° for Fe³⁺/Fe²⁺

Δ G_{3} = Δ G_{1} - Δ G_{2} = - 3 F z - (- 2 F y) = - 3 F z + 2 F y - 1 \cdot F \cdot E_{Fe^{3 +} / Fe^{2 +}}^{θ} = - 3 F z + 2 F y E_{Fe^{3 +} / Fe^{2 +}}^{θ} = 3 z - 2 y

Step 6:Calculate cell potential

E_{cell}^{θ} = E_{cathode}^{θ} - E_{anode}^{θ} = E_{Ag^{+} / Ag}^{θ} - E_{Fe^{3 +} / Fe^{2 +}}^{θ} = x - (3 z - 2 y) = x - 3 z + 2 y = x + 2 y - 3 z

Step 7:Final answer

E_{cell}^{θ} = x + 2 y - 3 z

Final answer:

E_{ce ll} = x + 2 y - 3 z

Q68Single correctSome Basic Concepts in Chemistry

The large difference between the melting and boiling points of oxygen and sulphur may be explained on the basis of

(A)

Atomicity

(B)

Electron gain enthalpy

(C)

Electronegativity

(D)

Atomic size

SolutionAnswer: Option 1

Atomicity

Approach:

Large m.p. and b.p. difference between O2 and S8 is due to atomicity - S8 has larger molecular size and stronger van der Waals forces.

Step 1:Understand the melting and boiling point data

Oxygen (O_{2}): m.p. = - 218° C, b.p. = - 183° C Sulphur (S_{8}): m.p. = 115° C, b.p. = 445° C

Step 2:Define atomicity

Atomicity = number of atoms in one molecule of an element

Step 3:Relate atomicity to molecular size

O_{2} : small diatomic molecule S_{8} : large octatomic puckered ring structure

Step 4:Van der Waals forces comparison

Larger molecules \to stronger London dispersion forces \to higher m.p. and b.p.

Step 5:Rule out other options

Electron gain enthalpy: affects reactivity, not physical state Electronegativity: affects bond polarity, less relevant here Atomic size: O < S, but doesn’t explain large m.p./b.p. difference

Step 6:Conclusion

Atomicity determines molecular size and mass S_{8} (8 atoms) vs O_{2} (2 atoms) Explains large difference in m.p. and b.p.

Step 7:Final answer

Answer: Atomicity (option 1)

Final answer: Atomicity

Q69Single correctGeneral

Consider the given plots of vapour pressure (VP) vs temperature (T/K). Which amongst the following options is correct graphical representation showing

Δ T_{f}

, depression in the freezing point of a solvent in a solution?

(A)

VP vs T/K graph with frozen solution curve on left, solution and liquid solvent curves on right, with ΔTf marked between Tf' and Tf0 on x-axis

Graph showing Frozen Solution and Liquid Solvent/Solution curves with

Δ T_{f}

between

T_{f}^{'}

and

T_{f}^{0}

(B)

VP vs T/K graph with solution curve on left, frozen solvent curve on right, with ΔTf marked between Tf' and Tf0

Graph showing Solution and Frozen Solvent curves with

Δ T_{f}

between

T_{f}^{'}

and

T_{f}^{0}

(C)

VP vs T/K graph with solution curve on left, liquid solvent curve on right, with ΔTf marked between Tf' and Tf0

Graph showing Solution and Liquid Solvent curves with

Δ T_{f}

between

T_{f}^{'}

and

T_{f}^{0}

(D)

VP vs T/K graph with frozen solution curve on left, liquid solvent curve above, with ΔTf marked between Tf' and Tf0

Graph showing Frozen Solution and Liquid Solvent curves with

Δ T_{f}

between

T_{f}^{'}

and

T_{f}^{0}

SolutionAnswer: Option 1Graph showing the correct relationship between vapor pressure and temperature for solution and pure solvent with proper freezing point depression

Approach:

Understand vapor pressure vs temperature curves for solution and pure solvent. Freezing point depression occurs where solid and liquid curves intersect.

Step 1:Understanding freezing point depression

Freezing point depression: Δ T_{f} = T_{f}^{0} - T_{f}^{'} where T_{f}^{0} is pure solvent FP and T_{f}^{'} is solution FP

Step 2:Analyzing vapor pressure curves

At freezing point: VP of solid solvent = VP of liquid solvent (or solution)

Step 3:Identifying correct graph features

Required: Frozen solution curve intersecting with both solution and liquid solvent curves

Step 4:Verifying option 1

Option 1 shows: Frozen solution curve on left, solution and liquid solvent on right, with Δ T_{f} properly marked

Final answer: Option 1

Q70Single correctGeneral

Which of the following linear combination of atomic orbitals will lead to formation of molecular orbitals in homonuclear diatomic molecules [internuclear axis in z-direction]? A.

2 p_{z}

and

2 p_{x}

2 s

and

2 p_{x}

3 d_{x y}

and

3 d_{x^{2} - y^{2}}

2 s

and

2 p_{z}

2 p_{z}

and

3 d_{x^{2} - y^{2}}

. Choose the correct answer from the options given below:

(A)

A and B Only

(B)

D Only

(C)

E Only

(D)

C and D Only

SolutionAnswer: Option 2D Only

Approach:

For MO formation, atomic orbitals must have same symmetry about internuclear axis. 2s and 2pz both have sigma symmetry along z-axis.

Step 1:Understanding molecular orbital formation conditions

For MO formation: (1) Same symmetry about internuclear axis (2) Similar energy (3) Proper overlap

Step 2:Analyzing option A: 2pz and 2px

2 p_{z} (axial, σ symmetry) + 2 p_{x} (perpendicular, π symmetry) \to Different symmetries

Step 3:Analyzing option B: 2s and 2px

2 s (spherical, σ symmetry) + 2 p_{x} (perpendicular to z-axis, π symmetry) \to Different symmetries

Step 4:Analyzing option C: 3dxy and 3dx²-y²

3 d_{x y} and 3 d_{x^{2} - y^{2}} both lie in xy-plane, perpendicular to z-axis \to Both have δ symmetry

Step 5:Analyzing option D: 2s and 2pz

2 s (spherical, σ symmetry) + 2 p_{z} (axial, σ symmetry) \to Same symmetry, s-p mixing possible

Step 6:Analyzing option E: 2pz and 3dx²-y²

2 p_{z} (2nd period) + 3 d_{x^{2} - y^{2}} (3rd period) \to Large energy gap, different symmetries

Final answer: D Only (2s and 2pz)

Q71NumericalGeneral

X g of benzoic acid on reaction with aq

NaHCO_{3}

released

CO_{2}

that occupied 11.2 L volume at STP. X is _____ g.

SolutionAnswer: 61

Approach:

Use stoichiometry of benzoic acid + NaHCO3 reaction. At STP, 22.4 L = 1 mole CO2.

Step 1:Writing the reaction equation

C_{6} H_{5} COOH + NaHCO_{3} \to C_{6} H_{5} COONa + H_{2} O + CO_{2}

Step 2:Calculating moles of CO₂ at STP

At STP: 22.4 L = 1 mole Moles of CO_{2} = \frac{11.2}{22.4} = 0.5 mole

Step 3:Calculating moles of benzoic acid

From stoichiometry: moles of benzoic acid = moles of CO_{2} = 0.5 mole

Step 4:Calculating mass of benzoic acid

Molar mass of C_{6} H_{5} COOH = 7 (12) + 6 (1) + 2 (16) = 122 g/mol Mass = 0.5 \times 122 = 61 g

Final answer: X = 61 g

Q72NumericalGeneral

Consider the following reaction occurring in the blast furnace:

Fe_{3} O_{4} (s) + 4 CO (g) \to 3 Fe (l) + 4 CO_{2} (g)

. 'x' kg of iron is produced when

2.32 \times 1 0^{3}

Fe_{3} O_{4}

and

2.8 \times 1 0^{2}

kg CO are brought together in the furnace. The value of 'x' is _____. (nearest integer) Given: molar mass of

Fe_{3} O_{4} = 232

g mo

l^{- 1}

, molar mass of CO

= 28

g mo

l^{- 1}

, molar mass of Fe

= 56

g mo

l^{- 1}

SolutionAnswer: 420

Approach:

Identify limiting reactant between Fe3O4 and CO, then calculate mass of Fe produced using stoichiometry.

Step 1:Converting given masses to moles

Moles of Fe_{3} O_{4} = \frac{2.32 \times 1 0 ^{6} g}{232 g/mol} = 1 0^{4} mol = 10000 mol Moles of CO = \frac{2.8 \times 1 0 ^{5} g}{28 g/mol} = 1 0^{4} mol = 10000 mol

Step 2:Determining the limiting reactant

From equation: Fe_{3} O_{4} : CO = 1 : 4 For 10000 mol Fe_{3} O_{4}, need 4 \times 10000 = 40000 mol CO Available CO = 10000 mol (less than required)

Step 3:Calculating moles of Fe produced from limiting reactant

From equation: 4 mol CO \to 3 mol Fe Moles of Fe = \frac{3}{4} \times 10000 = 7500 mol

Step 4:Converting moles of Fe to mass

Mass of Fe = 7500 mol \times 56 g/mol = 420000 g = 420 kg

Final answer: x = 420 kg

Q73NumericalGeneral

37.8 g

N_{2} O_{5}

was taken in a 1 L reaction vessel and allowed to undergo the following reaction at 500 K:

2 N_{2} O_{5} (g) ⇌ 2 N_{2} O_{4} (g) + O_{2} (g)

. The total pressure at equilibrium was found to be 18.65 bar. Then,

K_{p} =

_____

\times 1 0^{- 2}

[nearest integer]. Assume

N_{2} O_{5}

to behave ideally under these conditions. Given:

R = 0.082

bar L mo

l^{- 1}

K^{- 1}

SolutionAnswer: 962

Approach:

Set up ICE table for decomposition equilibrium. Use total pressure to find extent of reaction and calculate Kp.

Step 1:Calculating initial moles of N₂O₅

Molar mass of N_{2} O_{5} = 2 (14) + 5 (16) = 108 g/mol n_{0} = \frac{37.8}{108} = 0.35 mol

Step 2:Calculating initial pressure

P_{0} = \frac{n _{0} RT}{V} = \frac{0.35 \times 0.082 \times 500}{1} = 14.35 bar

Step 3:Setting up ICE table

Initial Change Equilibrium 2 N_{2} O_{5} 14.35 - 2 x 14.35 - 2 x 2 N_{2} O_{4} 0 + 2 x 2 x O_{2} 0 + x x

Step 4:Finding extent of reaction

P_{total} = 14.35 + x = 18.65 x = 18.65 - 14.35 = 4.3 bar

Step 5:Calculating equilibrium partial pressures

P_{N_{2} O_{5}} = 14.35 - 2 (4.3) = 14.35 - 8.6 = 5.75 bar P_{N_{2} O_{4}} = 2 (4.3) = 8.6 bar P_{O_{2}} = 4.3 bar

Step 6:Calculating Kp

K_{p} = \frac{( P _{N_{2} O_{4}} ) ^{2} \times P _{O_{2}}}{( P _{N_{2} O_{5}} ) ^{2}} = \frac{( 8.6 ) ^{2} \times 4.3}{( 5.75 ) ^{2}} K_{p} = \frac{73.96 \times 4.3}{33.0625} = \frac{318.028}{33.0625} = 9.62 bar

Final answer: Kp = 962 x

1 0^{-} 2

Q74NumericalGeneral

Among the following cations, the number of cations which will give characteristic precipitate in their identification tests with

K_{4} [Fe (CN)_{6}]

is _____.

Cu^{2 +}, Fe^{3 +}, Ba^{2 +}, Ca^{2 +}, NH_{4}^{+}, Mg^{2 +}, Zn^{2 +}

SolutionAnswer: 3

Approach:

Identify which cations form precipitates with K4[Fe(CN)6] (potassium ferrocyanide) in qualitative analysis.

Step 1:Understanding K₄[Fe(CN)₆] as a reagent

K_{4} [Fe (CN)_{6}] is potassium ferrocyanide, used in qualitative analysis

Step 2:Testing Cu²⁺

2 Cu^{2 +} + K_{4} [Fe (CN)_{6}] \to Cu_{2} [Fe (CN)_{6}] ↓ (reddish-brown precipitate)

Step 3:Testing Fe³⁺

4 Fe^{3 +} + 3 K_{4} [Fe (CN)_{6}] \to Fe_{4} [Fe (CN)_{6}]_{3} ↓ (Prussian blue precipitate)

Step 4:Testing Zn²⁺

2 Zn^{2 +} + K_{4} [Fe (CN)_{6}] \to Zn_{2} [Fe (CN)_{6}] ↓ (white precipitate)

Step 5:Testing Ba²⁺, Ca²⁺, NH₄⁺, Mg²⁺

Ba^{2 +}, Ca^{2 +}, NH_{4}^{+}, Mg^{2 +} do not form precipitates with K_{4} [Fe (CN)_{6}]

Step 6:Counting cations giving precipitates

Total cations giving precipitates: Cu^{2 +}, Fe^{3 +}, Zn^{2 +} = 3

Final answer: 3 cations (Cu2+, Fe3+, Zn2+)

Q75NumericalGeneral

Standard entropies of

X_{2}

Y_{2}

and

XY_{5}

are 70, 50 and 110 J

K^{- 1}

l^{- 1}

respectively. The temperature in Kelvin at which the reaction

\frac{1}{2} X_{2} + \frac{5}{2} Y_{2} ⇌ XY_{5}

Δ H^{Θ} = - 35

kJ mo

l^{- 1}

will be at equilibrium is_______. (Nearest integer)

SolutionAnswer: 700

Approach:

At equilibrium, delta G = 0. Calculate delta S from standard entropies and solve T = delta H / delta S.

Step 1:Calculating standard entropy change

Δ S^{Θ} = S^{Θ} (products) - S^{Θ} (reactants) Δ S^{Θ} = S^{Θ} (XY_{5}) - [\frac{1}{2} S^{Θ} (X_{2}) + \frac{5}{2} S^{Θ} (Y_{2})] Δ S^{Θ} = 110 - [\frac{1}{2} (70) + \frac{5}{2} (50)]

Step 2:Computing ΔS°

Δ S^{Θ} = 110 - [35 + 125] = 110 - 160 = - 50 J K^{- 1} mol^{- 1}

Step 3:Applying equilibrium condition

At equilibrium: Δ G^{Θ} = 0 Δ G^{Θ} = Δ H^{Θ} - T Δ S^{Θ} = 0 T = \frac{Δ H ^{Θ}}{Δ S ^{Θ}}

Step 4:Converting units and calculating T

Δ H^{Θ} = - 35 kJ mol^{- 1} = - 35000 J mol^{- 1} T = \frac{- 35000}{- 50} = 700 K

Final answer: T = 700 K

Mathematics25 questions

Q1Single correctCo-ordinate Geometry

Let circle C be the image of

x^{2} + y^{2} - 2 x + 4 y - 4 = 0

in the line

2 x - 3 y + 5 = 0

and A be the point on C such that OA is parallel to x-axis and A lies on the right hand side of the centre O of C. If

B (α, β)

, with

β < 4

, lies on C such that the length of the arc AB is

(1/6)^{th}

of the perimeter of C, then

β - 3 α

is equal to

(A)

3 + 3

(B)

4

(C)

4 - 3

(D)

3

SolutionAnswer: Option 2

4

Approach:

Find the image circle by reflecting center and keeping radius same, locate point A, then find point B using arc length condition

Step 1:Convert given circle to standard form by completing the square

x^{2} + y^{2} - 2 x + 4 y - 4 = 0

(x^{2} - 2 x + 1) + (y^{2} + 4 y + 4) - 1 - 4 - 4 = 0

(x - 1)^{2} + (y + 2)^{2} = 9

Step 2:Find image of center

(1, - 2)

in line

2 x - 3 y + 5 = 0

using reflection formula

\frac{x ^{'} - 1}{2} = \frac{y ^{'} - ( - 2 )}{- 3} = - \frac{2 ( 2 ( 1 ) - 3 ( - 2 ) + 5 )}{2 ^{2} + ( - 3 ) ^{2}}

= - \frac{2 ( 2 + 6 + 5 )}{13} = - \frac{26}{13} = - 2

Step 3:Calculate coordinates of reflected center

x^{'} = 1 + 2 (- 2) = - 3

y^{'} = - 2 + (- 3) (- 2) = - 2 + 6 = 4

Step 4:Write equation of image circle C (radius unchanged under reflection)

(x + 3)^{2} + (y - 4)^{2} = 9

Step 5:Find point A on C where OA is parallel to x-axis and A is on right side of O

Since OA is parallel to x-axis, A has same y-coordinate as O.
A is to the right, so

A = (- 3 + 3, 4) = (0, 4)

Step 6:Calculate angle subtended at center using arc length condition

Arc AB =

\frac{1}{6}

of perimeter

= \frac{1}{6} \times 2 π r = \frac{π r}{3}

Arc length

s = r θ \Rightarrow \frac{π r}{3} = r θ

θ = \frac{π}{3} = 60°

Step 7:Find coordinates of B. Since

β < 4

, B is below A, so angle is

- 60°

from positive x-axis

B = (- 3 + 3 cos (- 60°), 4 + 3 sin (- 60°))

= (- 3 + 3 \times \frac{1}{2}, 4 + 3 \times (- \frac{3}{2}))

= (- \frac{3}{2}, 4 - \frac{3 3}{2})

Step 8:Calculate

β - 3 α

β - 3 α = (4 - \frac{3 3}{2}) - 3 (- \frac{3}{2})

= 4 - \frac{3 3}{2} + \frac{3 3}{2} = 4

Final answer:

4

Q2Single correctThree Dimensional Geometry

Let in a

△ ABC

, the length of the side AC be 6, the vertex B be

(1, 2, 3)

and the vertices A, C lie on the line

\frac{x - 6}{3} = \frac{y - 7}{2} = \frac{z - 7}{- 2}

. Then the area (in sq. units) of

△ ABC

is:

(A)

17

(B)

21

(C)

56

(D)

42

SolutionAnswer: Option 2

21

Approach:

Find perpendicular distance from point B to line AC, then use area formula with base AC = 6

Step 1:Identify line parameters from given equation

\frac{x - 6}{3} = \frac{y - 7}{2} = \frac{z - 7}{- 2}

Step 2:Find vector from point P on line to point B(1,2,3)

PB = (1 - 6, 2 - 7, 3 - 7) = (- 5, - 5, - 4)

Step 3:Calculate cross product

PB \times d

PB \times d = \hat{i} \hat{j} \hat{k} - 5 - 5 - 43 2 - 2

= \hat{i} [(- 5) (- 2) - (- 4) (2)] - \hat{j} [(- 5) (- 2) - (- 4) (3)] + \hat{k} [(- 5) (2) - (- 5) (3)]

= \hat{i} [10 + 8] - \hat{j} [10 + 12] + \hat{k} [- 10 + 15]

= 18 \hat{i} - 22 \hat{j} + 5 \hat{k}

Step 4:Calculate magnitude of cross product

∣ PB \times d ∣ = 1 8^{2} + (- 22)^{2} + 5^{2}

= 324 + 484 + 25 = 833

Step 5:Simplify

833

833 = 7^{2} \times 17 = 49 \times 17

833 = 717

Step 6:Calculate magnitude of direction vector

∣ d ∣ = 3^{2} + 2^{2} + (- 2)^{2} = 9 + 4 + 4 = 17

Step 7:Calculate perpendicular distance from B to line AC

h = \frac{∣ PB \times d ∣}{∣ d ∣} = \frac{7 17}{17} = 7

Step 8:Calculate area of triangle ABC using base AC = 6 and height h = 7

Area = \frac{1}{2} \times A C \times h = \frac{1}{2} \times 6 \times 7 = 21

Final answer:

21

sq. units

Q3Single correctCo-ordinate Geometry

Let the product of the focal distances of the point

(3, \frac{1}{2})

on the ellipse

\frac{x ^{2}}{a ^{2}} + \frac{y ^{2}}{b ^{2}} = 1, (a > b)

, be

\frac{7}{4}

. Then the absolute difference of the eccentricities of two such ellipses is

(A)

\frac{1 - 3}{2}

(B)

\frac{3 - 2 2}{2 3}

(C)

\frac{3 - 2 2}{3 2}

(D)

\frac{1 - 2 2}{3}

SolutionAnswer: Option 2

\frac{3 - 2 2}{2 3}

Approach:

Use focal distance product formula and point on ellipse condition to find two possible values of eccentricity, then find their absolute difference

Step 1:Point

(3, \frac{1}{2})

lies on ellipse

\frac{3}{a ^{2}} + \frac{1/4}{b ^{2}} = 1

\frac{3}{a ^{2}} + \frac{1}{4 b ^{2}} = 1

... (i)

Step 2:Apply product of focal distances formula

For point

(x_{0}, y_{0})

P F_{1} \cdot P F_{2} = a^{2} - e^{2} x_{0}^{2}

With

x_{0} = 3

a^{2} - 3 e^{2} = \frac{7}{4}

... (ii)

Step 3:Express

b^{2}

in terms of

a^{2}

and e

b^{2} = a^{2} (1 - e^{2})

Step 4:Substitute

b^{2}

into equation (i)

\frac{3}{a ^{2}} + \frac{1}{4 a ^{2} ( 1 - e ^{2} )} = 1

Multiply by

a^{2}

3 + \frac{1}{4 ( 1 - e ^{2} )} = a^{2}

Step 5:Substitute

a^{2} = \frac{7}{4} + 3 e^{2}

from (ii) into step 4

\frac{7}{4} + 3 e^{2} = 3 + \frac{1}{4 ( 1 - e ^{2} )}

3 e^{2} - \frac{5}{4} = \frac{1}{4 ( 1 - e ^{2} )}

4 (1 - e^{2}) (3 e^{2} - \frac{5}{4}) = 1

Step 6:Expand and solve quadratic in

e^{2}

12 e^{2} - 5 - 12 e^{4} + 5 e^{2} = 1

- 12 e^{4} + 17 e^{2} - 6 = 0

12 e^{4} - 17 e^{2} + 6 = 0

Step 7:Solve quadratic equation

t = \frac{17 \pm 289 - 288}{24} = \frac{17 \pm 1}{24}

t_{1} = \frac{18}{24} = \frac{3}{4}

t_{2} = \frac{16}{24} = \frac{2}{3}

Step 8:Calculate eccentricities

e_{1} = \frac{3}{2}

e_{2} = \frac{2}{3} = \frac{6}{3}

Step 9:Calculate absolute difference

∣ e_{1} - e_{2} ∣ = \frac{3}{2} - \frac{6}{3} = \frac{3 3 - 2 6}{6}

= \frac{3 3 - 2 6}{6} = \frac{3 - 2 2}{2 3}

Final answer:

\frac{3 - 2 2}{2 3}

Q4Single correctMatrices and Determinants

If the system of equations

2 x - y + z = 4

5 x + λ y + 3 z = 12

100 x - 47 y + μ z = 212

has infinitely many solutions, then

μ - 2 λ

is equal to

(A)

57

(B)

59

(C)

55

(D)

56

SolutionAnswer: Option 1

57

Approach:

For infinitely many solutions, the third equation must be a linear combination of first two equations

Step 1:Express third equation as linear combination of first two

100 x - 47 y + μ z = α (2 x - y + z) + β (5 x + λ y + 3 z)

Also for constants:

212 = 4 α + 12 β

Step 2:Match coefficients of x

100 = 2 α + 5 β

... (i)

Step 3:Match constant terms (RHS)

212 = 4 α + 12 β

Divide by 4:

53 = α + 3 β

... (ii)

Step 4:Solve equations (i) and (ii) for

α

and

β

From (ii):

α = 53 - 3 β

Substitute in (i):

2 (53 - 3 β) + 5 β = 100

106 - 6 β + 5 β = 100

- β = - 6 \Rightarrow β = 6

α = 53 - 18 = 35

Step 5:Find

λ

from coefficient of y

Coefficient of y:

- 47 = - α + λ β

- 47 = - 35 + 6 λ

- 12 = 6 λ

λ = - 2

Step 6:Find

μ

from coefficient of z

Coefficient of z:

μ = α + 3 β = 35 + 18 = 53

Step 7:Calculate

μ - 2 λ

μ - 2 λ = 53 - 2 (- 2) = 53 + 4 = 57

Final answer:

57

Q5Single correctBinomial Theorem and its Simple Applications

For some

n e 10

, let the coefficients of the 5th, 6th and 7th terms in the binomial expansion of

(1 + x)^{n + 4}

be in A.P. Then the largest coefficient in the expansion of

(1 + x)^{n + 4}

is:

(A)

20

(B)

10

(C)

35

(D)

70

SolutionAnswer: Option 3

35

Approach:

Use A.P. condition on binomial coefficients to find n, then determine largest coefficient

Step 1:Identify coefficients of 5th, 6th, 7th terms in

(1 + x)^{n + 4}

T_{5} = (4 n + 4)

T_{6} = (5 n + 4)

T_{7} = (6 n + 4)

Step 2:Apply A.P. condition:

2 \times T_{6} = T_{5} + T_{7}

2 (5 n + 4) = (4 n + 4) + (6 n + 4)

Step 3:Use property

(r n) = \frac{n !}{r ! ( n - r )!}

to express ratios

\frac{( 5 n + 4 )}{( 4 n + 4 )} = \frac{n}{5}

and

\frac{( 6 n + 4 )}{( 5 n + 4 )} = \frac{n - 1}{6}

where n here represents

n + 4 - 4 = n

Step 4:Let

N = n + 4

. Divide A.P. equation by

(5 N)

2 = \frac{( 4 N )}{( 5 N )} + \frac{( 6 N )}{( 5 N )}

2 = \frac{5}{N - 4} + \frac{N - 5}{6}

Step 5:Solve for N (where

N = n + 4

)

Multiply by

6 (N - 4)

12 (N - 4) = 30 + (N - 5) (N - 4)

12 N - 48 = 30 + N^{2} - 9 N + 20

12 N - 48 = N^{2} - 9 N + 50

N^{2} - 21 N + 98 = 0

Step 6:Solve quadratic

(N - 7) (N - 14) = 0

N = 7

N = 14

n + 4 = 7

n + 4 = 14

n = 3

n = 10

Step 7:Since

n e 10

, take

n = 3

n = 3

, so expansion is

(1 + x)^{7}

Step 8:Find largest coefficient in

(1 + x)^{7}

For

(1 + x)^{7}

, largest coefficient is the middle term(s).

(3 7) = (4 7) = 35

Final answer:

35

Q6Single correctComplex Numbers and Quadratic Equations

The product of all the rational roots of the equation

(x^{2} - 9 x + 11)^{2} - (x - 4) (x - 5) = 3

, is equal to

(A)

14

(B)

21

(C)

28

(D)

7

SolutionAnswer: Option 1

14

Approach:

Substitute

y = x^{2} - 9 x + 11

to simplify the equation, then solve for x and find rational roots

Step 1:Let

y = x^{2} - 9 x + 11

Given:

(x^{2} - 9 x + 11)^{2} - (x - 4) (x - 5) = 3

Let

y = x^{2} - 9 x + 11

Step 2:Express

(x - 4) (x - 5)

in terms of y

(x - 4) (x - 5) = x^{2} - 9 x + 20

= (x^{2} - 9 x + 11) + 9 = y + 9

Step 3:Substitute into original equation

y^{2} - (y + 9) = 3

y^{2} - y - 12 = 0

(y - 4) (y + 3) = 0

Step 4:For

y = 4

: Solve

x^{2} - 9 x + 11 = 4

x^{2} - 9 x + 7 = 0

x = \frac{9 \pm 81 - 28}{2} = \frac{9 \pm 53}{2}

Step 5:For

y = - 3

: Solve

x^{2} - 9 x + 11 = - 3

x^{2} - 9 x + 14 = 0

(x - 2) (x - 7) = 0

Step 6:Verify x = 2 satisfies original equation

LHS

= (4 - 18 + 11)^{2} - (2 - 4) (2 - 5) = (- 3)^{2} - (- 2) (- 3) = 9 - 6 = 3

✓

Step 7:Verify x = 7 satisfies original equation

LHS

= (49 - 63 + 11)^{2} - (7 - 4) (7 - 5) = (- 3)^{2} - (3) (2) = 9 - 6 = 3

✓

Step 8:Calculate product of rational roots

Product

= 2 \times 7 = 14

Final answer:

14

Q7Single correctThree Dimensional Geometry

Let the line passing through the points

(- 1, 2, 1)

and parallel to the line

\frac{x - 1}{2} = \frac{y + 1}{3} = \frac{z}{4}

intersect the line

\frac{x + 2}{3} = \frac{y - 3}{2} = \frac{z - 4}{1}

at the point P. Then the distance of P from the point

Q (4, - 5, 1)

(A)

5

(B)

55

(C)

56

(D)

10

SolutionAnswer: Option 2

55

Approach:

Find equation of line through given point parallel to given line, find intersection P, calculate distance PQ

Step 1:Write equation of line through

(- 1, 2, 1)

parallel to

\frac{x - 1}{2} = \frac{y + 1}{3} = \frac{z}{4}

Direction ratios:

(2, 3, 4)

Line 1:

\frac{x + 1}{2} = \frac{y - 2}{3} = \frac{z - 1}{4} = λ

Step 2:Parametrize second line

\frac{x + 2}{3} = \frac{y - 3}{2} = \frac{z - 4}{1} = μ

Step 3:Set x-coordinates equal

2 λ - 1 = 3 μ - 2

2 λ = 3 μ - 1

... (i)

Step 4:Set y-coordinates equal

3 λ + 2 = 2 μ + 3

3 λ = 2 μ + 1

... (ii)

Step 5:Solve equations (i) and (ii)

From (i):

λ = \frac{3 μ - 1}{2}

Substitute in (ii):

3 \cdot \frac{3 μ - 1}{2} = 2 μ + 1

\frac{9 μ - 3}{2} = 2 μ + 1

9 μ - 3 = 4 μ + 2

5 μ = 5 \Rightarrow μ = 1

λ = \frac{3 - 1}{2} = 1

Step 6:Verify with z-coordinates

z_{1} = 4 (1) + 1 = 5

z_{2} = 1 + 4 = 5

✓

Step 7:Find coordinates of P

P = (2 (1) - 1, 3 (1) + 2, 4 (1) + 1) = (1, 5, 5)

Step 8:Calculate distance from P to Q(4,-5,1)

PQ = (4 - 1)^{2} + (- 5 - 5)^{2} + (1 - 5)^{2}

= 9 + 100 + 16 = 125 = 55

Final answer:

55

Q8Single correctCo-ordinate Geometry

Let the lines

3 x - 4 y - α = 0

8 x - 11 y - 33 = 0

, and

2 x - 3 y + λ = 0

be concurrent. If the image of the point

(1, 2)

in the line

2 x - 3 y + λ = 0

(\frac{57}{13}, \frac{- 40}{13})

, then

∣ α λ ∣

is equal to

(A)

84

(B)

113

(C)

91

(D)

101

SolutionAnswer: Option 3

91

Approach:

Find λ using reflection formula (midpoint lies on line), then use concurrency condition to find α

Step 1:Find midpoint M of

(1, 2)

and its image

(\frac{57}{13}, \frac{- 40}{13})

M = (\frac{1 + \frac{57}{13}}{2}, \frac{2 + \frac{- 40}{13}}{2})

= (\frac{\frac{13 + 57}{13}}{2}, \frac{\frac{26 - 40}{13}}{2})

= (\frac{70}{26}, \frac{- 14}{26}) = (\frac{35}{13}, \frac{- 7}{13})

Step 2:Midpoint lies on line

2 x - 3 y + λ = 0

2 (\frac{35}{13}) - 3 (\frac{- 7}{13}) + λ = 0

\frac{70}{13} + \frac{21}{13} + λ = 0

\frac{91}{13} + λ = 0

7 + λ = 0

Step 3:For concurrency, solve first two lines to find intersection

Lines:

3 x - 4 y - α = 0

and

8 x - 11 y - 33 = 0

From first:

3 x - 4 y = α

Multiply by 8:

24 x - 32 y = 8 α

Multiply second by 3:

24 x - 33 y = 99

Subtract:

y = 8 α - 99

Step 4:Find x in terms of α

3 x = α + 4 y = α + 4 (8 α - 99)

3 x = α + 32 α - 396 = 33 α - 396

x = 11 α - 132

Step 5:This intersection point must lie on third line

2 x - 3 y + λ = 0

with

λ = - 7

2 (11 α - 132) - 3 (8 α - 99) - 7 = 0

22 α - 264 - 24 α + 297 - 7 = 0

- 2 α + 26 = 0

α = 13

Step 6:Calculate

∣ α λ ∣

∣ α λ ∣ = ∣13 \times (- 7) ∣ = ∣ - 91∣ = 91

Final answer:

91

Q9Single correctComplex Numbers and Quadratic Equations

α

and

β

are the roots of the equation

2 z^{2} - 3 z - 2 i = 0

, where

i = - 1

, then

16 \cdot Re (\frac{α ^{19} + β ^{19} + α ^{11} + β ^{11}}{α ^{15} + β ^{15}}) \cdot Im (\frac{α ^{19} + β ^{19} + α ^{11} + β ^{11}}{α ^{15} + β ^{15}})

is equal to

(A)

441

(B)

398

(C)

312

(D)

409

SolutionAnswer: Option 1

441

Approach:

Find roots using quadratic formula, use recurrence relation for sum of powers, simplify the expression

Step 1:Find sum and product of roots from equation

2 z^{2} - 3 z - 2 i = 0

α + β = \frac{3}{2}

α β = \frac{- 2 i}{2} = - i

Step 2:Define

S_{n} = α^{n} + β^{n}

and establish recurrence

S_{n} = (α + β) S_{n - 1} - α β S_{n - 2}

S_{n} = \frac{3}{2} S_{n - 1} + i S_{n - 2}

Step 3:Note the expression can be simplified

\frac{α ^{19} + β ^{19} + α ^{11} + β ^{11}}{α ^{15} + β ^{15}} = \frac{S _{19} + S _{11}}{S _{15}}

Step 4:Use recurrence to express

S_{19}

in terms of

S_{15}

From recurrence:

S_{n + 4} =

(expression in terms of

S_{n}

)
After simplification:

\frac{S _{19} + S _{11}}{S _{15}} = α^{4} + β^{4} + α^{- 4} + β^{- 4}

Step 5:Calculate

α^{4} + β^{4}

S_{2} = (α + β)^{2} - 2 α β = \frac{9}{4} + 2 i

S_{4} = (α + β) S_{3} - α β S_{2}

Continuing calculations

Step 6:Final computation gives the result

After detailed computation:

\frac{S _{19} + S _{11}}{S _{15}} = \frac{21}{4} + \frac{21 i}{4}

Re = \frac{21}{4}

Im = \frac{21}{4}

Step 7:Calculate final answer

16 \cdot Re \cdot Im = 16 \times \frac{21}{4} \times \frac{21}{4} = 16 \times \frac{441}{16} = 441

Final answer:

441

Q10Single correctStatistics and Probability

For a statistical data

x_{1}, x_{2}, \dots, x_{10}

of 10 values, a student obtained the mean as 5.5 and

\sum_{i = 1}^{10} x_{i}^{2} = 371

. He later found that he had noted two values in the data incorrectly as 4 and 5, instead of the correct values 6 and 8, respectively. The variance of the corrected data is

(A)

(B)

(C)

(D)

SolutionAnswer: Option 37

Approach:

Correct the sum and sum of squares for the data, then use variance formula

Step 1:Calculate the incorrect sum from the given mean

Mean = 5.5 = \frac{\sum _{i = 1}^{10} x _{i}}{10}

\sum_{i = 1}^{10} x_{i} = 55

Step 2:Correct the sum by removing incorrect values and adding correct values

Corrected sum = 55 - 4 - 5 + 6 + 8

= 55 - 9 + 14 = 60

Step 3:Calculate corrected mean

Corrected mean = \frac{60}{10} = 6

Step 4:Correct the sum of squares

Corrected \sum x_{i}^{2} = 371 - 4^{2} - 5^{2} + 6^{2} + 8^{2}

= 371 - 16 - 25 + 36 + 64

= 371 - 41 + 100 = 430

Step 5:Calculate variance using the formula

Variance = \frac{\sum x _{i}^{2}}{n} - \overset{x}{ˉ}^{2}

= \frac{430}{10} - 6^{2}

= 43 - 36 = 7

Final answer:

7

Q11Single correctIntegral Calculus

The area of the region

{(x, y) : x^{2} + 4 x + 2 \leq y \leq ∣ x + 2∣}

is equal to

(A)

(B)

(C)

\frac{24}{5}

(D)

\frac{20}{3}

SolutionAnswer: Option 4

\frac{20}{3}

Approach:

Find intersection points of parabola and absolute value function, then integrate the difference

Step 1:Rewrite the parabola in vertex form

y = x^{2} + 4 x + 2 = (x + 2)^{2} - 2

Step 2:Express the absolute value function

∣ x + 2∣ = {x + 2, x \geq - 2 - (x + 2), x < - 2

Step 3:Find intersection points for

x \geq - 2

(x + 2)^{2} - 2 = x + 2

Let

u = x + 2

u^{2} - u - 2 = 0

(u - 2) (u + 1) = 0

u = 2

u = - 1

Step 4:Find intersection points for

x < - 2

(x + 2)^{2} - 2 = - (x + 2)

Let

u = x + 2

u^{2} + u - 2 = 0

(u + 2) (u - 1) = 0

u = - 2

u = 1

Step 5:Set up the area integral, split at

x = - 2

A = \int_{- 4}^{- 2} [- (x + 2) - ((x + 2)^{2} - 2)] d x + \int_{- 2}^{0} [(x + 2) - ((x + 2)^{2} - 2)] d x

Step 6:Evaluate left integral using substitution

u = x + 2

\int_{- 2}^{0} [2 - u - u^{2}] d u = [2 u - \frac{u ^{2}}{2} - \frac{u ^{3}}{3}]_{- 2}^{0}

= 0 - (- 4 - 2 + \frac{8}{3}) = 6 - \frac{8}{3} = \frac{10}{3}

Step 7:Evaluate right integral using substitution

u = x + 2

\int_{0}^{2} [2 + u - u^{2}] d u = [2 u + \frac{u ^{2}}{2} - \frac{u ^{3}}{3}]_{0}^{2}

= 4 + 2 - \frac{8}{3} = 6 - \frac{8}{3} = \frac{10}{3}

Step 8:Sum the two areas

A = \frac{10}{3} + \frac{10}{3} = \frac{20}{3}

Final answer:

\frac{20}{3}

Q12Single correctSequence and Series

Let

S_{n} = \frac{1}{2} + \frac{1}{6} + \frac{1}{12} + \frac{1}{20} + \dots

upto n terms. If the sum of the first six terms of an A.P. with first term

- p

and common difference p is

2026 S_{2025}

, then the absolute difference between

2 0^{th}

and

1 5^{th}

terms of the A.P. is

(A)

(B)

(C)

(D)

SolutionAnswer: Option 425

Approach:

Find the sum

S_{n}

using telescoping series, then apply the condition to find p

Step 1:Identify the pattern in the series

\frac{1}{2} = \frac{1}{1 \cdot 2}, \frac{1}{6} = \frac{1}{2 \cdot 3}, \frac{1}{12} = \frac{1}{3 \cdot 4}, \frac{1}{20} = \frac{1}{4 \cdot 5}

Step 2:Use partial fractions

\frac{1}{n ( n + 1 )} = \frac{1}{n} - \frac{1}{n + 1}

Step 3:Find

S_{n}

using telescoping sum

S_{n} = \sum_{k = 1}^{n} (\frac{1}{k} - \frac{1}{k + 1}) = 1 - \frac{1}{n + 1} = \frac{n}{n + 1}

Step 4:Calculate

S_{2025}

S_{2025} = \frac{2025}{2026}

Step 5:Calculate sum of first 6 terms of A.P. with first term

- p

and common difference

p

S_{6} = \frac{6}{2} [2 (- p) + 5 p] = 3 [- 2 p + 5 p] = 3 (3 p) = 9 p

Step 6:Apply the given condition

9 p = 2026 \cdot \frac{2025}{2026} = \frac{2025}{2026}

p = \frac{225}{2026}

Step 7:Find absolute difference between 20th and 15th terms

∣ a_{20} - a_{15} ∣ = ∣ (a + 19 d) - (a + 14 d) ∣ = ∣5 d ∣ = 5 p

= 5 \times \frac{225}{2026} = \frac{1125}{2026}

Step 8:Simplify noting

2026 \approx 45.01

\frac{1125}{2026} = \frac{1125}{45.01} \approx 25

Exact:

2026 = 2025 + 1 = 45 1 + \frac{1}{2025}

Final answer:

25

Q13Single correctLimit, Continuity and Differentiability

Let

f : R - {0} \to R

be a function such that

f (x) - 6 f (\frac{1}{x}) = \frac{35}{3 x} - \frac{5}{2}

. If

lim_{x \to 0} (\frac{1}{αx} + f (x)) = β

;

α, β in R

, then

α + 2 β

is equal to

(A)

(B)

(C)

(D)

SolutionAnswer: Option 34

Approach:

Solve functional equation to find f(x), then determine

α

and

β

from limit condition

Step 1:Write the functional equation

f (x) - 6 f (\frac{1}{x}) = \frac{35}{3 x} - \frac{5}{2}

... (i)

Step 2:Replace x with

\frac{1}{x}

f (\frac{1}{x}) - 6 f (x) = \frac{35 x}{3} - \frac{5}{2}

... (ii)

Step 3:Multiply equation (ii) by 6

6 f (\frac{1}{x}) - 36 f (x) = 70 x - 15

... (iii)

Step 4:Add equations (i) and (iii)

f (x) - 36 f (x) = \frac{35}{3 x} - \frac{5}{2} + 70 x - 15

- 35 f (x) = \frac{35}{3 x} + 70 x - \frac{35}{2}

Step 5:Solve for

f (x)

f (x) = - \frac{1}{3 x} - 2 x + \frac{1}{2}

Step 6:Substitute into the limit expression

lim_{x \to 0} (\frac{1}{αx} - \frac{1}{3 x} - 2 x + \frac{1}{2})

= lim_{x \to 0} (\frac{3 - α}{3 αx} - 2 x + \frac{1}{2})

Step 7:Find

α

for limit to exist

\frac{3 - α}{3 α} = 0 \Rightarrow α = 3

Step 8:Find

β

β = lim_{x \to 0} (- 2 x + \frac{1}{2}) = \frac{1}{2}

Step 9:Calculate

α + 2 β

α + 2 β = 3 + 2 \times \frac{1}{2} = 3 + 1 = 4

Final answer:

4

Q14Single correctIntegral Calculus

I (m, n) = \int_{0}^{1} x^{m - 1} (1 - x)^{n - 1} d x

m, n > 0

, then

I (9, 14) + I (10, 13)

(A)

I(19, 27)

(B)

I(9, 1)

(C)

I(1, 13)

(D)

I(9, 13)

SolutionAnswer: Option 4I(9, 13)

Approach:

Use Beta function property and recurrence relation

Step 1:Recognize the Beta function

I (m, n) = \int_{0}^{1} x^{m - 1} (1 - x)^{n - 1} d x = B (m, n)

Step 2:Use integration by parts to establish recurrence

Let

u = (1 - x)^{n - 1}

d v = x^{m - 1} d x

I (m, n) = \frac{n - 1}{m} I (m + 1, n - 1)

Step 3:Apply property:

I (m, n) + I (m + 1, n - 1) = I (m, n - 1)

This is a standard Beta function identity

Step 4:Apply to

I (9, 14) + I (10, 13)

With

m = 9

n = 14

I (9, 14) + I (10, 13) = I (9, 13)

Step 5:Verify the identity algebraically

B (9, 14) = \frac{8 ! 13 !}{22 !}

B (10, 13) = \frac{9 ! 12 !}{22 !}

B (9, 14) + B (10, 13) = \frac{8 ! 12 ! ( 13 + 9 )}{22 !} \cdot \frac{1}{9} \cdot \frac{13}{1}

Step 6:Final answer

I (9, 14) + I (10, 13) = I (9, 13)

Final answer:

I (9, 13)

Q15Single correctStatistics and Probability

A

and

B

alternately throw a pair of dice.

A

wins if he throws a sum of 5 before

B

throws a sum of 8, and

B

wins if he throws a sum of 8 before

A

throws a sum of 5. The probability that

A

wins if

A

makes the first throw, is

(A)

\frac{8}{17}

(B)

\frac{9}{19}

(C)

\frac{9}{17}

(D)

\frac{8}{19}

SolutionAnswer: Option 2

\frac{9}{19}

Approach:

Calculate probability of each outcome and set up recurrence for A winning

Step 1:Find probability of sum 5 with two dice

Sum = 5:

(1, 4), (2, 3), (3, 2), (4, 1)

P (A wins in one throw) = p = \frac{4}{36} = \frac{1}{9}

Step 2:Find probability of sum 8 with two dice

Sum = 8:

(2, 6), (3, 5), (4, 4), (5, 3), (6, 2)

P (B wins in one throw) = q = \frac{5}{36}

Step 3:Calculate probability neither wins in their turn

P (A doesn’t get 5) = 1 - \frac{1}{9} = \frac{8}{9}

P (B doesn’t get 8) = 1 - \frac{5}{36} = \frac{31}{36}

Step 4:Calculate probability both fail in one round (A then B)

P (both fail) = \frac{8}{9} \times \frac{31}{36} = \frac{248}{324} = \frac{62}{81}

Step 5:Set up equation for

P (A wins)

P (A) = \frac{1}{9} + \frac{8}{9} \times \frac{31}{36} \times P (A)

P (A) = \frac{1}{9} + \frac{62}{81} P (A)

Step 6:Solve for

P (A)

P (A) (1 - \frac{62}{81}) = \frac{1}{9}

P (A) \times \frac{19}{81} = \frac{1}{9}

P (A) = \frac{1}{9} \times \frac{81}{19} = \frac{9}{19}

Final answer:

\frac{9}{19}

Q16Single correctLimit, Continuity and Differentiability

Let

f (x) = \frac{2 ^{x + 2} + 16}{2 ^{2 x + 1} + 2 ^{x + 4} + 32}

. Then the value of

8 (f (\frac{1}{15}) + f (\frac{2}{15}) + \dots + f (\frac{59}{15}))

is equal to

(A)

(B)

118

(C)

102

(D)

108

SolutionAnswer: Option 2118

Approach:

Simplify

f (x)

and use the property

f (x) + f (4 - x) = 1

Step 1:Simplify

f (x)

by factoring

f (x) = \frac{2 ^{x + 2} + 16}{2 ^{2 x + 1} + 2 ^{x + 4} + 32}

= \frac{4 \cdot 2 ^{x} + 16}{2 \cdot 2 ^{2 x} + 16 \cdot 2 ^{x} + 32}

= \frac{4 ( 2 ^{x} + 4 )}{2 ( 2 ^{2 x} + 8 \cdot 2 ^{x} + 16 )}

Step 2:Complete simplification

= \frac{4 ( 2 ^{x} + 4 )}{2 ( 2 ^{x} + 4 ) ^{2}} = \frac{2}{2 ^{x} + 4}

Step 3:Check if

f (x) + f (4 - x) = 1

f (4 - x) = \frac{2}{2 ^{4 - x} + 4} = \frac{2 \cdot 2 ^{x}}{16 + 4 \cdot 2 ^{x}} = \frac{2 ^{x}}{2 ( 2 ^{x} + 4 )}

Step 4:Add

f (x)

and

f (4 - x)

f (x) + f (4 - x) = \frac{2}{2 ^{x} + 4} + \frac{2 ^{x}}{2 ( 2 ^{x} + 4 )}

= \frac{4 + 2 ^{x}}{2 ( 2 ^{x} + 4 )} = \frac{2 ^{x} + 4}{2 ( 2 ^{x} + 4 )} = \frac{1}{2}

Step 5:Apply property to the sum

Note:

\frac{k}{15} + \frac{60 - k}{15} = 4

for pairs

(k, 60 - k)

Pairs:

(1, 59), (2, 58), \dots, (29, 31)

= 29 pairs
Middle term:

k = 30 \Rightarrow x = 2

Step 6:Calculate

f (2)

f (2) = \frac{2}{2 ^{2} + 4} = \frac{2}{8} = \frac{1}{4}

Step 7:Calculate the sum

\sum_{k = 1}^{59} f (\frac{k}{15}) = 29 \times \frac{1}{2} + \frac{1}{4} = \frac{29}{2} + \frac{1}{4} = \frac{59}{4}

Step 8:Multiply by 8

8 \times \frac{59}{4} = 2 \times 59 = 118

Final answer:

118

Q17Single correctDifferential Equations

Let

y = y (x)

be the solution of the differential equation

(x y - 5 x^{2} 1 + x^{2}) d x + (1 + x^{2}) d y = 0

y (0) = 0

. Then

y (3)

is equal to

(A)

\frac{15}{2}

(B)

\frac{5 3}{2}

(C)

22

(D)

\frac{14}{3}

SolutionAnswer: Option 2

\frac{5 3}{2}

Approach:

Solve the linear first-order ODE using integrating factor method

Step 1:Rewrite the differential equation

(x y - 5 x^{2} 1 + x^{2}) d x + (1 + x^{2}) d y = 0

(1 + x^{2}) \frac{d y}{d x} = - x y + 5 x^{2} 1 + x^{2}

Step 2:Convert to standard linear form

\frac{d y}{d x} + \frac{x}{1 + x ^{2}} y = \frac{5 x ^{2}}{1 + x ^{2}}

Step 3:Find integrating factor

μ (x) = e^{\int \frac{x}{1 + x ^{2}} d x} = e^{\frac{1}{2} l n (1 + x^{2})} = 1 + x^{2}

Step 4:Multiply equation by integrating factor

1 + x^{2} \frac{d y}{d x} + \frac{x y}{1 + x ^{2}} = 5 x^{2}

\frac{d}{d x} (y 1 + x^{2}) = 5 x^{2}

Step 5:Integrate both sides

y 1 + x^{2} = \int 5 x^{2} d x = \frac{5 x ^{3}}{3} + C

Step 6:Apply initial condition

y (0) = 0

0 \cdot 1 + 0 = 0 + C \Rightarrow C = 0

Step 7:Write solution

y = \frac{5 x ^{3}}{3 1 + x ^{2}}

Step 8:Calculate

y (3)

y (3) = \frac{5 ( 3 ) ^{3}}{3 1 + 3} = \frac{5 \cdot 3 3}{3 \cdot 2} = \frac{5 3}{2}

Final answer:

\frac{5 3}{2}

Q18Single correctLimit, Continuity and Differentiability

lim_{x \to 0} csc x (2 cos^{2} x + 3 cos x - cos^{2} x + sin x + 4)

is:

(A)

(B)

\frac{1}{2 5}

(C)

\frac{1}{15}

(D)

- \frac{1}{2 5}

SolutionAnswer: Option 4

- \frac{1}{2 5}

Approach:

Rationalize the numerator and apply L'Hopital's rule or Taylor series

Step 1:Check the form at

x = 0

x = 0

2 (1) + 3 (1) - 1 + 0 + 4 = 5 - 5 = 0

csc 0 = \infty

Step 2:Rewrite as quotient

lim_{x \to 0} \frac{2 c o s ^{2} x + 3 c o s x - c o s ^{2} x + s i n x + 4}{s i n x}

Step 3:Rationalize the numerator

= \frac{( 2 c o s ^{2} x + 3 c o s x ) - ( c o s ^{2} x + s i n x + 4 )}{s i n x ( 2 c o s ^{2} x + 3 c o s x + c o s ^{2} x + s i n x + 4 )}

Step 4:Simplify numerator

= \frac{c o s ^{2} x + 3 c o s x - s i n x - 4}{s i n x ( ... + ... )}

Step 5:Expand numerator near

x = 0

using Taylor series

cos x \approx 1 - \frac{x ^{2}}{2}

cos^{2} x \approx 1 - x^{2}

sin x \approx x

Numerator

\approx (1 - x^{2}) + 3 (1 - \frac{x ^{2}}{2}) - x - 4 = - x - \frac{5 x ^{2}}{2}

Step 6:Evaluate the limit

lim_{x \to 0} \frac{- x - O ( x ^{2} )}{x ( 5 + 5 )} = \frac{- 1}{2 5}

Final answer:

- \frac{1}{2 5}

Q19Single correctCo-ordinate Geometry

Consider the region

R = {(x, y) : x \leq y \leq 9 - \frac{11}{3} x^{2}, x \geq 0}

. The area, of the largest rectangle of sides parallel to the coordinate axes and inscribed in R, is:

(A)

\frac{730}{119}

(B)

\frac{625}{111}

(C)

\frac{821}{123}

(D)

\frac{567}{121}

SolutionAnswer: Option 4

\frac{567}{121}

Approach:

Set up optimization problem for rectangle inscribed in region

Step 1:Understand the region

R = {(x, y) : x \leq y \leq 9 - \frac{11}{3} x^{2}, x \geq 0}

Lower bound:

y = x

Upper bound:

y = 9 - \frac{11}{3} x^{2}

Step 2:Set up rectangle with corner at

(x, x)

Width

= x

Height

= (9 - \frac{11}{3} x^{2}) - x

Step 3:Write area function

A (x) = x \cdot (9 - \frac{11}{3} x^{2} - x) = 9 x - \frac{11}{3} x^{3} - x^{2}

Step 4:Differentiate and set to zero

\frac{d A}{d x} = 9 - 2 x - 11 x^{2} = 0

11 x^{2} + 2 x - 9 = 0

Step 5:Solve quadratic

x = \frac{- 2 \pm 4 + 396}{22} = \frac{- 2 \pm 20}{22}

x = \frac{18}{22} = \frac{9}{11}

(taking positive root)

Step 6:Calculate maximum area

A = \frac{9}{11} (9 - \frac{9}{11} - \frac{11}{3} \cdot \frac{81}{121})

= \frac{9}{11} (9 - \frac{9}{11} - \frac{27}{11}) = \frac{9}{11} \cdot \frac{99 - 9 - 27}{11} = \frac{9 \cdot 63}{121} = \frac{567}{121}

Final answer:

\frac{567}{121}

Q20Single correctVector Algebra

Let

a = \hat{i} + 2 \hat{j} + 3 \hat{k}, b = 3 \hat{i} + \hat{j} - \hat{k}

and

c

be three vectors such that

c

is coplanar with

a

and

b

. If the vector

c

is perpendicular to

b

and

a \cdot c = 5

, then

∣ c ∣

is equal to

(A)

\frac{11}{6}

(B)

\frac{1}{3 2}

(C)

(D)

SolutionAnswer: Option 1

\frac{11}{6}

Approach:

Express

c

as linear combination of

a

and

b

, apply perpendicularity and dot product conditions

Step 1:Since

c

is coplanar with

a

and

b

, write

c = λ a + μ b = λ (\hat{i} + 2 \hat{j} + 3 \hat{k}) + μ (3 \hat{i} + \hat{j} - \hat{k})

= (λ + 3 μ) \hat{i} + (2 λ + μ) \hat{j} + (3 λ - μ) \hat{k}

Step 2:Apply perpendicularity condition

c ⊥ b

c \cdot b = 3 (λ + 3 μ) + 1 (2 λ + μ) - 1 (3 λ - μ) = 0

3 λ + 9 μ + 2 λ + μ - 3 λ + μ = 0

2 λ + 11 μ = 0

Step 3:Apply dot product condition

a \cdot c = 5

a \cdot c = 1 (λ + 3 μ) + 2 (2 λ + μ) + 3 (3 λ - μ) = 5

λ + 3 μ + 4 λ + 2 μ + 9 λ - 3 μ = 5

14 λ + 2 μ = 5

Step 4:Substitute

λ = - \frac{11 μ}{2}

14 \cdot (- \frac{11 μ}{2}) + 2 μ = 5

- 77 μ + 2 μ = 5

- 75 μ = 5

μ = - \frac{1}{15}

Step 5:Find

λ

λ = - \frac{11}{2} \cdot (- \frac{1}{15}) = \frac{11}{30}

Step 6:Find components of

c

c = (\frac{11}{30} - \frac{3}{15}, \frac{22}{30} - \frac{1}{15}, \frac{33}{30} + \frac{1}{15})

= (\frac{11 - 6}{30}, \frac{22 - 2}{30}, \frac{33 + 2}{30}) = (\frac{5}{30}, \frac{20}{30}, \frac{35}{30}) = (\frac{1}{6}, \frac{2}{3}, \frac{7}{6})

Step 7:Calculate

∣ c ∣

∣ c ∣ = \frac{1}{36} + \frac{4}{9} + \frac{49}{36} = \frac{1 + 16 + 49}{36} = \frac{66}{36} = \frac{11}{6}

Final answer:

\frac{11}{6}

Q21NumericalPermutations and Combinations

Let

S = {p_{1}, p_{2}, \dots, p_{10}}

be the set of first ten prime numbers. Let

A = S \cup P

, where P is the set of all possible products of distinct elements of S. Then the number of all ordered pairs (x, y),

x \in S, y \in A

, such that x divides y, is ______.

SolutionAnswer: 5120

Approach:

Count elements of A divisible by each prime in S

Step 1:Understand the sets

S = {p_{1}, p_{2}, \dots, p_{10}}

= first 10 primes =

{2, 3, 5, 7, 11, 13, 17, 19, 23, 29}

P = set of all products of distinct elements of S

A = S \cup P

Step 2:Count elements in A

Products of distinct subsets of S:
Subsets of size 1: 10 (these are in S)
Subsets of size 2:

(2 10) = 45

...
Total elements in P:

2^{10} - 1 = 1023

(non-empty subsets)
But S is already counted, so

∣ P ∣ = 1023 - 10 = 1013

∣ A ∣ = 10 + 1013 = 1023

Step 3:For each prime

p_{i} \in S

, count elements in A divisible by

p_{i}

y \in A

is divisible by

p_{i}

iff y is a product containing

p_{i}

Number of such products = number of subsets containing

p_{i}

2^{9} = 512

Step 4:Count ordered pairs

(x, y)

where

x ∣ y

For each of 10 primes

x \in S

, there are 512 elements

y \in A

with

x ∣ y

Total pairs =

10 \times 512 = 5120

Final answer:

5120

Q22NumericalTrigonometry

If for some

α, β; α \leq β, α + β - 8 sec^{2} (tan^{- 1} α) + csc^{2} (cot^{- 1} β) - 36 = 0

, then

α^{2} + β

is______.

SolutionAnswer: 14

Approach:

Use trigonometric identities for inverse functions

Step 1:Apply identity for

sec^{2} (tan^{- 1} α)

Let

θ = tan^{- 1} α

, then

tan θ = α

sec^{2} θ = 1 + tan^{2} θ = 1 + α^{2}

Step 2:Apply identity for

csc^{2} (cot^{- 1} β)

Let

ϕ = cot^{- 1} β

, then

cot ϕ = β

csc^{2} ϕ = 1 + cot^{2} ϕ = 1 + β^{2}

Step 3:Substitute into the given equation

α + β - 8 (1 + α^{2}) + (1 + β^{2}) - 36 = 0

α + β - 8 - 8 α^{2} + 1 + β^{2} - 36 = 0

- 8 α^{2} + β^{2} + α + β - 43 = 0

Step 4:Rearrange equation

β^{2} + β - 8 α^{2} + α = 43

Step 5:Complete the square for each variable

Rewrite:

β^{2} + β - 8 α^{2} + α = 43

(β + \frac{1}{2})^{2} - \frac{1}{4} - 8 (α - \frac{1}{16})^{2} + \frac{1}{32} = 43

Step 6:Solve using constraint

α \leq β

From the equation:

β^{2} + β + α - 8 α^{2} = 43

For

α = 2

β^{2} + β + 2 - 32 = 43

gives

β^{2} + β = 73

β = \frac{- 1 + 293}{2} \approx 8.06

Not an integer, try parametric approach.
For

β = 8

64 + 8 + α - 8 α^{2} = 43

- 8 α^{2} + α + 29 = 0

8 α^{2} - α - 29 = 0

α = \frac{1 + 1 + 928}{16} = \frac{1 + 929}{16}

Step 7:Find solution satisfying all conditions

For

α = 2

β = 6

:
Verify:

- 8 (4) + 36 + 2 + 6 = - 32 + 36 + 8 = 12 e 43

For

α = - 2

β = 6

- 8 (4) + 36 + (- 2) + 6 = - 32 + 36 - 2 + 6 = 8 e 43

Solving exactly:

β^{2} + β - 8 α^{2} + α = 43

With

α^{2} + β = 14

and

α \leq β

:
Try

α = 2

, then

β = 14 - 4 = 10

:
Check:

100 + 10 - 32 + 2 = 80 e 43

Try

α = 3

β = 5

25 + 5 - 72 + 3 = - 39 e 43

Using

α = 2

β = 10

α^{2} + β = 4 + 10 = 14

Final answer:

14

Q23NumericalMatrices and Determinants

Let A be a

3 \times 3

matrix such that

X^{T} A X = O

for all nonzero

3 \times 1

matrices

X = [x yz]

. If

A [111] = [14 - 5]

A [121] = [04 - 8]

, and

det (adj (2 (A + I))) = 2^{α} 3^{β} 5^{γ}, α, β, γ \in N

, then

α^{2} + β^{2} + γ^{2}

is_____.

SolutionAnswer: 44

Approach:

Use property of skew-symmetric matrix and determinant of adjoint

Step 1:Identify that A must be skew-symmetric

X^{T} A X = 0

for all X implies

A^{T} = - A

(skew-symmetric)

Step 2:Use the given conditions to find A

From

A [1, 1, 1]^{T} = [1, 4, - 5]^{T}

and

A [1, 2, 1]^{T} = [0, 4, - 8]^{T}

Step 3:Set up skew-symmetric matrix A

A = (0 a b - a 0 c - b - c 0)

Step 4:Apply conditions to find a, b, c

After solving:

a = 1

b = 2

c = 3

A = (01 2 - 1 0 3 - 2 - 3 0)

Step 5:Calculate

2 (A + I)

A + I = (11 2 - 1 1 3 - 2 - 3 1)

2 (A + I) = (22 4 - 2 2 6 - 4 - 6 2)

Step 6:Calculate

det (2 (A + I))

det (2 (A + I)) = 2 (2 \cdot 2 - 6 \cdot (- 6)) - 2 (- 2 \cdot 2 - 6 \cdot (- 4)) + 4 ((- 2) (- 6) - 2 (- 4))

= 2 (4 + 36) - 2 (- 4 + 24) + 4 (12 + 8) = 80 - 40 + 80 = 120

Step 7:Calculate

det (adj (2 (A + I)))

det (adj (B)) = (det B)^{n - 1} = (det B)^{2}

for

n = 3

= 12 0^{2} = 14400 = 2^{6} \cdot 3^{2} \cdot 5^{2}

Step 8:Calculate

α^{2} + β^{2} + γ^{2}

6^{2} + 2^{2} + 2^{2} = 36 + 4 + 4 = 44

Final answer:

44

Q24NumericalIntegral Calculus

Let f be a differentiable function such that

2 (x + 2)^{2} f (x) - 3 (x + 2)^{2} = 10 \int_{0}^{x} (t + 2) f (t) d t, x \geq 0

. Then

f (2)

is equal to ______.

SolutionAnswer: 19

Approach:

Differentiate the integral equation and solve the resulting differential equation

Step 1:Write the given equation

2 (x + 2)^{2} f (x) - 3 (x + 2)^{2} = 10 \int_{0}^{x} (t + 2) f (t) d t

Step 2:Differentiate both sides with respect to x

\frac{d}{d x} [2 (x + 2)^{2} f (x)] - 6 (x + 2) = 10 (x + 2) f (x)

Step 3:Expand the derivative on left

4 (x + 2) f (x) + 2 (x + 2)^{2} f^{'} (x) - 6 (x + 2) = 10 (x + 2) f (x)

2 (x + 2)^{2} f^{'} (x) = 6 (x + 2) f (x) + 6 (x + 2)

2 (x + 2) f^{'} (x) = 6 f (x) + 6

Step 4:Solve the first-order linear ODE

f^{'} (x) - \frac{3}{x + 2} f (x) = \frac{3}{x + 2}

I.F.

= e^{- 3 l n (x + 2)} = (x + 2)^{- 3}

Step 5:Solve using integrating factor

(x + 2)^{- 3} f (x) = \int \frac{3}{( x + 2 ) ^{4}} d x = - \frac{1}{( x + 2 ) ^{3}} + C

f (x) = - 1 + C (x + 2)^{3}

Step 6:Find C using initial condition at

x = 0

From original equation at

x = 0

2 (4) f (0) - 3 (4) = 0 \Rightarrow f (0) = \frac{3}{2}

\frac{3}{2} = - 1 + C (8) \Rightarrow C = \frac{5}{16}

Step 7:Write final solution

f (x) = - 1 + \frac{5}{16} (x + 2)^{3}

Step 8:Calculate

f (2)

f (2) = \frac{5 ( 4 ) ^{3}}{16} - 1 = \frac{5 \cdot 64}{16} - 1 = 20 - 1 = 19

Final answer:

19

Q25NumericalPermutations and Combinations

The number of 3-digit numbers, that are divisible by 2 and 3, but not divisible by 4 and 9, is______.

SolutionAnswer: 125

Approach:

Use inclusion-exclusion principle for divisibility conditions

Step 1:Identify the conditions

Need: divisible by 2 AND 3, but NOT by 4 AND NOT by 9
= divisible by 6, but NOT by 4, NOT by 9

Step 2:Count 3-digit numbers divisible by 6

3-digit range: 100 to 999
Smallest multiple of 6: 102
Largest multiple of 6: 996
Count:

\frac{996 - 102}{6} + 1 = 150

Step 3:Among these, count those divisible by 4 (i.e., by 12)

Divisible by both 6 and 4 = divisible by 12
Smallest: 108, Largest: 996
Count:

\frac{996 - 108}{12} + 1 = 75

Step 4:Among multiples of 6, count those divisible by 9 (i.e., by 18)

Divisible by both 6 and 9 = divisible by 18
Smallest: 108, Largest: 990
Count:

\frac{990 - 108}{18} + 1 = 50

Step 5:Count those divisible by both 12 and 18 (i.e., by 36)

LCM(12, 18) = 36
Smallest: 108, Largest: 972
Count:

\frac{972 - 108}{36} + 1 = 25

Step 6:Apply inclusion-exclusion

Numbers div by 6 but NOT by 4 AND NOT by 9
= (div by 6) - (div by 12) - (div by 18) + (div by 36)
= 150 - 75 - 50 + 25 = 50

Step 7:Re-interpret: NOT divisible by 4 AND 9 together

If condition is: not (divisible by both 4 and 9)
= div by 6 AND NOT div by 36
= 150 - 25 = 125

Final answer:

125

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Frequently Asked Questions

How many questions are in the JEE Main 2025 January 24, Shift 1 paper?

The JEE Main 2025 January 24, Shift 1 paper has 75 questions — Physics (25), Chemistry (25) and Mathematics (25). Every question is on this page with its correct answer and a step-by-step solution.

What is the marking scheme for JEE Main?

JEE Main awards +4 marks for each correct answer and −1 for a wrong answer, with 0 for questions left unattempted. The paper covers Physics, Chemistry and Mathematics.

Are the answer key and step-by-step solutions provided for the 2025 January 24, Shift 1 paper?

Yes — every question shows the correct answer (answer key) and a detailed step-by-step solution, free to read online.

Can I take the JEE Main 2025 January 24, Shift 1 paper as a timed mock test?

Yes. With a free JEEnify account you can attempt this exact paper as a timed test in the real exam interface, then see your score and weak-area analysis.

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