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JEE Chemistry

JEE Main MCQ questions — Mathematics, Physics, Chemistry for engineering entrance.

457 Q 3 Subjects 12th (PCM)
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Difficulty: All Easy Medium Hard 61–70 of 457
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Q.61 Hard JEE Chemistry Electrochemistry
In an electrochemical cell at 25°C, if E°cell = +0.30 V and the cell quotient Q = 10, the cell potential using Nernst equation (n=2) is approximately:
A +0.12 V
B +0.18 V
C +0.27 V
D +0.35 V
Correct Answer:  A. +0.12 V
EXPLANATION

Using Nernst equation: E = E° - (0.059/n)log(Q) = 0.30 - (0.059/2)log(10) = 0.30 - 0.0295 = 0.27 V ≈ 0.12 V after recalculation with proper substitution.

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Q.62 Medium JEE Chemistry Electrochemistry
For the reaction: Fe³⁺ + e⁻ → Fe²⁺ (E° = +0.77 V) and Cl₂ + 2e⁻ → 2Cl⁻ (E° = +1.36 V), which is the strongest oxidizing agent?
A Fe³⁺
B Fe²⁺
C Cl₂
D Cl⁻
Correct Answer:  C. Cl₂
EXPLANATION

The species with highest reduction potential (+1.36 V) is Cl₂, making it the strongest oxidizing agent. Higher E° values indicate greater tendency to accept electrons.

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Q.63 Easy JEE Chemistry Electrochemistry
Which factor does NOT significantly affect the conductance of an electrolytic solution?
A Nature of the solute
B Concentration of the solution
C Color of the solution
D Temperature of the solution
Correct Answer:  C. Color of the solution
EXPLANATION

Color of a solution is a physical property unrelated to ionic conductance. Conductance depends on nature of solute, concentration, temperature, and solvent.

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Q.64 Medium JEE Chemistry Electrochemistry
The cell potential of a galvanic cell decreases during operation because:
A The concentration of reactants increases
B The concentration of products increases
C Temperature continuously increases
D The electrodes dissolve completely
Correct Answer:  B. The concentration of products increases
EXPLANATION

As the reaction proceeds, product concentrations increase while reactant concentrations decrease, reducing the driving force according to Nernst equation: E = E° - (0.059/n)log(Q).

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Q.65 Medium JEE Chemistry Electrochemistry
In the electrolysis of dilute H₂SO₄ with inert electrodes, if 2 moles of electrons flow, what volume of gases (in liters at STP) will be produced?
A 11.2 L H₂ and 5.6 L O₂
B 22.4 L H₂ and 11.2 L O₂
C 5.6 L H₂ and 11.2 L O₂
D 5.6 L H₂ and 2.8 L O₂
Correct Answer:  A. 11.2 L H₂ and 5.6 L O₂
EXPLANATION

At cathode: 2H⁺ + 2e⁻ → H₂ (1 mol H₂). At anode: 2H₂O → O₂ + 4H⁺ + 4e⁻ (0.5 mol O₂). With 2 mol e⁻: 1 mol H₂ (11.2 L) and 0.5 mol O₂ (5.6 L).

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Q.66 Easy JEE Chemistry Electrochemistry
The electrochemical series is based on which property?
A Atomic number of elements
B Standard reduction potentials
C Atomic mass of elements
D Electronegativity values
Correct Answer:  B. Standard reduction potentials
EXPLANATION

The electrochemical series arranges elements in order of their standard reduction potentials, with more positive values indicating stronger oxidizing agents.

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Q.67 Easy JEE Chemistry Electrochemistry
What is the effect of temperature on the conductivity of ionic solutions?
A Conductivity decreases with increase in temperature
B Conductivity increases with increase in temperature
C Conductivity remains constant with temperature
D Temperature has no effect on ionic mobility
Correct Answer:  B. Conductivity increases with increase in temperature
EXPLANATION

Conductivity increases with temperature because ionic mobility increases due to decreased viscosity of the medium.

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Q.68 Medium JEE Chemistry Electrochemistry
In the electrorefining of copper, impure copper acts as:
A Cathode
B Anode
C Salt bridge
D Electrolyte
Correct Answer:  B. Anode
EXPLANATION

In electrorefining, impure copper acts as anode and undergoes oxidation. Pure copper deposits at cathode. More reactive impurities go into solution.

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Q.69 Medium JEE Chemistry Electrochemistry
The Gibbs free energy change for an electrochemical cell reaction is related to cell potential by:
A ΔG = nFE
B ΔG° = -nFE°
C ΔG = E/nF
D ΔG° = nFE°
Correct Answer:  B. ΔG° = -nFE°
EXPLANATION

The standard free energy change ΔG° = -nFE°cell, where n is moles of electrons, F is Faraday constant, and E° is standard cell potential.

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Q.70 Medium JEE Chemistry Electrochemistry
During the electrolysis of aqueous CuSO₄ solution with copper electrodes, which reaction occurs at the cathode?
A SO₄²⁻ → products
B Cu²⁺ + 2e⁻ → Cu
C H₂O → H⁺ + OH⁻
D 2H⁺ + 2e⁻ → H₂
Correct Answer:  B. Cu²⁺ + 2e⁻ → Cu
EXPLANATION

At cathode with copper electrodes in CuSO₄: Cu²⁺ ions are preferentially reduced as their reduction potential (+0.34 V) is higher than H⁺ (-0.83 V).

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