Electrochemistry MCQs Question and Answer in Engineering Chemistry

1

For the concentration cell, M|M⁺ (aq, 0.01 mol/dm³)| |M⁺ (aq), 0.1 mol/dm³|M the EMF (E) of the cell at a temperature (T) equals

A) $$2.303\frac{{RT}}{F}$$ B) $$ - 2.303\frac{{RT}}{F}$$ C) $$E_{{M^ + }|m}^ \circ + 2.303\frac{{RT}}{F}$$ D) $$E_{{M^ + }|m}^ \circ - 2.303\frac{{RT}}{F}$$

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Answer & Solution

Answer: Option A

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2

The activity of water at 11 bar and 298 K is

A) 1.101 B) 1.007 C) 0.998 D) 0.898

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Answer & Solution

Answer: Option B

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3

Given that E°(Fe³⁺, Fe) = -0.4 V and E°(Fe²⁺, Fe) = -0.44 V, the value of E°(Fe³⁺, Fe²⁺) is

A) 0.76V B) -0.40 V C) -0.76 V D) 0.40 V

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Answer & Solution

Answer: Option A

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4

According to the Debye-Huckel limiting law, if the concentration of a dilute aqueous solution of KCl is increased 4-fold, the value of In γ_z (γ_z is the molar mean ionic activity coefficient) will

A) decrease by a factor of 2 B) increase by a factor of 2 C) decrease by a factor of 4 D) increase by a factor of 4

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Answer: Option A

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5

Given the standard potential for the following half-cell reaction at 298 K,
Cu⁺(aq) + e^- → Cu(s); E° = 0.52 V
Cu²⁺(aq) + e^- → Cu⁺(aq); E° = 0.16 V
Calculate the ΔG° (kJ) for the reaction, [2Cu⁺(aq) → Cu(s) + Cu²⁺]

A) -34.740 B) -65.720 C) -69.480 D) -131.440

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Answer & Solution

Answer: Option A

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6

A student recorded a polarogram of 2.0 mM Cd²⁺ solution and forget to add KCl solution. What type of error do you expect in his results?

A) Only migration current will be observed B) Only diffusion current will be observed C) Both migration current as well as diffusion current will be observed D) Both catalytic current as well as diffusion current will be observed

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Answer & Solution

Answer: Option D

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7

For a 2 molal aqueous NaCl solution, the mean ionic activity coefficient $$\left( {{\gamma _ \pm }} \right)$$ and the Debye-Huckel Limiting Law constant (A) are related as

A) $$\log {\gamma _ \pm } = \sqrt 2 A$$ B) $$\log {\gamma _ \pm } = - \sqrt 2 A$$ C) $${\gamma _ \pm } = {10^4}$$ D) $${\gamma _ \pm } = {10^{ - 4}}$$

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Answer & Solution

Answer: Option B

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8

The standard reduction potentials at 298 K for single electrodes are given below.

Electrode	Electrode potential (volt)
Mg²⁺ /Mg	-2.34
Zn²⁺ /Zn	-0.76
Fe²⁺ /Fe	-0.44

From this we can infer that

A) Zn can reduce both Mg²⁺ and Fe²⁺ B) Fe can reduce both Mg²⁺ and Zn²⁺ C) Mg can reduce both Zn²⁺ and Fe²⁺ D) Mg can reduce Zn²⁺ but not Fe²⁺

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Answer & Solution

Answer: Option C

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9

For the reaction, Hg₂Cl₂(s) + H₂(g) → 2Hg(liq) + 2HCl(aq), the correct representation of the cell and the thermodynamic properties ΔG, ΔH and ΔS at 298 K respectively, are (Given: E₂₉₈ = 0.2684 V and temperature coefficient = 3 × 10^-4 VK^-1)

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Answer & Solution

Answer: Option A

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10

The Nernst equation for the reaction, A²⁺ + 2e^- → B, in terms of the free energy change is

A) ΔG = ΔG° + 2.303 RT log $$\frac{{\left[ B \right]}}{{\left[ A \right]}}$$ B) ΔG = ΔG° - 2.303 RT log $$\frac{{\left[ B \right]}}{{\left[ A \right]}}$$ C) -ΔG = -ΔG° + 2.303 RT log $$\frac{{\left[ B \right]}}{{\left[ A \right]}}$$ D) ΔG = -ΔG° + 2.303 RT log $$\frac{{\left[ B \right]}}{{\left[ A \right]}}$$

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Answer & Solution

Answer: Option A

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