Which of the following lanthanide elements has the electronic configuration [Xe]4f⁷5d¹6s²?

The correct answer is A: Gadolinium (Gd). Gadolinium has atomic number 64 with configuration [Xe]4f⁷5d¹6s². The half-filled 4f⁷ configuration makes Gd exceptionally stable. This is the only lanthanide with a 5d electron, making it unique among the lanthanide series.

Which of the following elements forms the most stable hydride?

The correct answer is B: F. Fluorine forms HF which is the most stable hydride among halogens due to the strong H-F bond (high bond energy ~570 kJ/mol), resulting from fluorine's high electronegativity.

At 25°C, the rate constant is 3 × 10⁻² s⁻¹ and at 35°C it is 6 × 10⁻² s⁻¹. What is the temperature coefficient (Q₁₀) for this reaction?

The correct answer is B: 2. Q₁₀ = k(T+10)/k(T) = (6 × 10⁻²)/(3 × 10⁻²) = 2. For typical reactions, Q₁₀ = 2-3

In a reaction, the rate increases by a factor of 8 when [A] doubles and by a factor of 2 when [B] doubles. What is the overall order of the reaction?

The correct answer is C: 4. When [A] doubles, rate increases by 8 = 2³, so order w.r.t. A = 3. When [B] doubles, rate increases by 2 = 2¹, so order w.r.t. B = 1. Overall order = 3 + 1 = 4.

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Physical Chemistry

Chemistry questions for JEE Main — Physical, Organic, Inorganic Chemistry.

52 Q 5 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 52

Topics in JEE Chemistry

All Physical Chemistry 100 Organic Chemistry 100 Inorganic Chemistry 100 Electrochemistry 100 Chemical Kinetics 57

Q.1 Medium Physical Chemistry

A solution contains 0.1 M weak acid HA (Ka = 1×10⁻⁵). The degree of ionization is approximately:

A 0.01

B 0.001

C 0.1

D 0.0316

Correct Answer: D. 0.0316

EXPLANATION

For weak acid: α = √(Ka/C) = √(1×10⁻⁵/0.1) = √(1×10⁻⁴) = 0.01 or 1%. Using exact formula: α ≈ 0.0316 (3.16%)

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Q.2 Medium Physical Chemistry

For the reaction 2A(g) ⇌ B(g) + C(g), if initial pressure is 2 atm and degree of dissociation is 0.5, what is the total pressure at equilibrium?

A 3 atm

B 2.5 atm

C 4 atm

D 1.5 atm

Correct Answer: A. 3 atm

EXPLANATION

Initial: 2 atm of A. At equilibrium with α = 0.5: A dissociates to (1-0.5)×2 = 1 atm, producing B and C each at 0.5 atm. Total = 1 + 0.5 + 0.5 = 2 atm × (1 + α) = 2 × 1.5 = 3 atm

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Q.3 Medium Physical Chemistry

The molar conductivity of a weak electrolyte increases with dilution because:

A Conductivity of ions increases

B Degree of ionization increases

C Number of ions decreases

D Viscosity of solution increases

Correct Answer: B. Degree of ionization increases

EXPLANATION

At higher dilutions, weak electrolytes ionize more completely, increasing degree of ionization and thus molar conductivity

Test

Q.4 Medium Physical Chemistry

For an exothermic reaction at 298 K, which condition favors spontaneity?

A ΔH > 0, ΔS > 0

B ΔH < 0, ΔS < 0

C ΔH < 0, ΔS > 0

D ΔH > 0, ΔS < 0

Correct Answer: C. ΔH < 0, ΔS > 0

EXPLANATION

ΔG = ΔH - TΔS; For spontaneity ΔG < 0. Exothermic (ΔH < 0) with ΔS > 0 always gives ΔG < 0

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Q.5 Medium Physical Chemistry

The rate law for reaction is: rate = k[A]²[B]. If [A] is doubled and [B] is halved, how does rate change?

A Increases by 2 times

B Decreases by 2 times

C Remains same

D Increases by 4 times

Correct Answer: A. Increases by 2 times

EXPLANATION

New rate = k(2[A])²(0.5[B]) = k × 4[A]² × 0.5[B] = 2k[A]²[B] = 2 × original rate

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Q.6 Medium Physical Chemistry

Which pair of substances will form an ideal solution?

A Ethanol and water

B Benzene and toluene

C Acetone and chloroform

D Acetic acid and water

Correct Answer: B. Benzene and toluene

EXPLANATION

Benzene and toluene are both aromatic hydrocarbons with similar molecular structures, forming nearly ideal solutions

Test

Q.7 Medium Physical Chemistry

At 25°C, for a cell with E°cell = 0.92 V, what is ΔG°? (F = 96485 C/mol)

A -88.8 kJ/mol

B -177.6 kJ/mol

C -44.4 kJ/mol

D -266.4 kJ/mol

Correct Answer: B. -177.6 kJ/mol

EXPLANATION

ΔG° = -nFE°; For bivalent ion transfer: ΔG° = -2 × 96485 × 0.92 ≈ -177.6 kJ/mol

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Q.8 Medium Physical Chemistry

Ksp of AgCl is 1.8 × 10⁻¹⁰. What is the molar solubility in 0.1 M NaCl solution?

A 1.8 × 10⁻⁹ M

B 1.8 × 10⁻¹⁰ M

C 4.24 × 10⁻⁵ M

D 1.34 × 10⁻⁵ M

Correct Answer: A. 1.8 × 10⁻⁹ M

EXPLANATION

In presence of 0.1 M Cl⁻: Ksp = [Ag⁺][Cl⁻]; 1.8 × 10⁻¹⁰ = s × 0.1; s = 1.8 × 10⁻⁹ M

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Q.9 Medium Physical Chemistry

What is the pH of a buffer solution containing 0.1 M acetic acid and 0.15 M sodium acetate? (Ka = 1.8 × 10⁻⁵)

A 4.92

B 5.22

C 4.74

D 5.48

Correct Answer: B. 5.22

EXPLANATION

Using Henderson-Hasselbalch: pH = pKa + log([salt]/[acid]) = 4.74 + log(0.15/0.1) = 4.74 + 0.48 = 5.22

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Q.10 Medium Physical Chemistry

For a first-order reaction with half-life of 10 minutes, what percentage of reactant remains after 30 minutes?

A 50%

B 25%

C 12.5%

D 6.25%

Correct Answer: C. 12.5%

EXPLANATION

After 3 half-lives (30 min): (1/2)³ = 1/8 = 12.5% remains

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