Conductance and Electrochemical Cells - Electrochemistry - Life Sciences Previous Year Questions

1

2007 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2007

A fuel cell is based on the idea of the reaction H₂(g) + ½ O₂(g) → H₂O(l) generating electricity. The standard free energy change (ΔG°) for this reaction at 298 K is –237.13 kJ/mol. The standard cell potential for the system at 298 K is (1 Faraday = 96500 coulombs)

A

2.457 volts

B

1.228 volts

C

-1.228 volts

D

-2.457 volts

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2

2008 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2008

An electrochemical cell of the following representation was found to be a galvanic cell, where ‘A’ and ‘B’ represent different metals.
\[A(s) \mid A^{2+} (aq) \; 1 \; M \; \| \; B^{2+} (aq) \; 1M \mid B(s)\]
Which of the following statements with respect to the cell is correct?

A

The cell converts electrical energy to chemical energy spontaneously.

B

The cell uses electrical energy to deposit ‘A’ and dissolve ‘B’ spontaneously.

C

\(A^{2+}/A\) is a stronger reducing agent than \(B^{2+}/B\).

D

\(A^{2+}/A\) is a stronger oxidizing agent than \(B^{2+}/B\).

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3

2008 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2008

The limiting molar conductivities of some species are given in \((S \; cm^2 \; mol^{-1})\) units:
\[\Lambda_m^0(HCl) = 425.9; \; \Lambda_m^0(NaCl) = 126.4; \; \Lambda_m^0(H^+) = 349.6\]
Find the limiting molar conductivity of \(Na^+\) ion.

A

50.1

B

76.3

C

299.5

D

476.0

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4

2009 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2009

Given the following standard electrode potentials at 25 °C: \( \frac{1}{2} Fe^{2+} + e^- = \frac{1}{2} Fe(s) ; E^0 = -0.440 \, V \) \( Fe^{3+} + e^- = Fe^{2+} ; E^0 = +0.771 \, V \) The standard electrode potential at 25 °C for \( Fe^{3+} + 3e^- = Fe(s) \) is

A

\(-0.036 \, V \)

B

\(-0.331 \, V \)

C

\(-0.662 \, V \)

D

\(-2.422 \, V \)

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5

2010 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2010

A battery delivers a steady current of 1.25 A for 90 minutes. The total charge 'Q' (in Coulomb units) is

A

6750

B

1012.5

C

112.5

D

12.5

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6

2012 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2012

The value of standard half cell potential of Cu²⁺, Cu couple (E°_{Cu²⁺, Cu}) is 0.34 V. A wire of pure copper is immersed into a solution of copper nitrate. If the measured cell potential against standard hydrogen electrode at 298 K is 0.24 V, the molar concentration of copper nitrate is {Assume activity of Cu²⁺ = [Cu²⁺]}.

A

4.1 × 10^-4 M

B

2.0 × 10^-2 M

C

3.4 × 10^-2 M

D

1.8 × 10^-1 M

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7

2013 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2013

The molar conductance at infinite dilution (in S m² mol^-1) of acetic acid is

A

1028 × 10^-4

B

820.4 × 10^-4

C

690.5 × 10^-4

D

390.8 × 10^-4

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8

2013 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2013

If the molar conductance of an acetic acid solution is \(15.2 \times 10^{-4}\) S m² mol^-1, then the percentage (%) dissociation of acetic acid in the solution will be

A

3.89

B

2.20

C

1.85

D

1.48

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9

2016 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2016

For a weak acid at 298 K the molar conductivities (in ohm^-1 m² mol^-1) at infinite dilution and 0.04 mol dm^-3 are \( 4.3 \times 10^{-2} \) and \( 1.0 \times 10^{-2} \), respectively. The degree of dissociation of the acid (0.04 mol dm^-3) at 298 K is ______________.

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10

2017 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2017

The EMF for the following cell at 298.15 K is
Ag(s) | Ag⁺(aq., 0.01 M) || Ag⁺(aq., 1.0 M) | Ag(s)
(Standard reduction potential for Ag⁺ + e⁻ → Ag is -0.80 V)

A

0.12 V

B

0.68 V

C

0.80 V

D

0.92 V

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11

2018 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2018

The standard reduction potential (E°) for the conversion of Cr₂O₇²⁻ to Cr³⁺ at 25 °C in an aqueous solution of pH 3.0 is 1.33 V. The concentrations of Cr₂O₇²⁻ and Cr³⁺ are 1.0 × 10⁻⁴ M and 1.0 × 10⁻³ M, respectively. Then the potential of this half-cell reaction is (Given: Faraday constant = 96500 C mol⁻¹, Gas constant R = 8.314 J K⁻¹ mol⁻¹)

A

1.04 V

B

0.94 V

C

0.84 V

D

0.74 V

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12

2019 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2019

Given the standard reduction potentials, E°(Cu²⁺/Cu) = 0.34 V and E°(Ag⁺/Ag) = 0.80 V, the standard free energy change (ΔG°) for the reaction
Cu(s) + 2Ag⁺(aq) → Cu²⁺(aq) + 2Ag(s)
in kJ mol⁻¹ (rounded off to one decimal place; F= 96500 C mol⁻¹), is ____

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13

2020 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2020

The standard potential ($E^0_{cell}$) for a cell reaction given below is +0.7 V. The standard reaction free energy ($\Delta_r G^0$) for this cell is ______ kJ mol⁻¹ (correct up to two decimal places). (Given: Faraday constant, F = 96500 C mol⁻¹) $\text{Au}^{3+} (aq) + 3 \text{Ag} (s) \longrightarrow \text{Au} (s) + 3 \text{Ag}^+ (aq)$

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14

2021 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2021

Given the standard reduction potentials, $E^\circ_{Mg^{2+}/Mg} = -2.37 \text{ V}$ and $E^\circ_{Ag^+/Ag} = 0.80 \text{ V}$, the potential of the following cell
Ag⁺(aq., 1 mM) + Mg(s) ⇌ Ag(s) + Mg²⁺(aq., 0.2 M)
at 25 °C is ________ V (rounded off to two decimal places).
(Given: Faraday constant = 96500 C mol⁻¹, Gas constant R = 8.314 J K⁻¹ mol⁻¹)

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15

2022 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2022

Molar conductance of monobromoacetic acid at infinite dilution is calculated to be \(x \times 10^{-4} \text{ S m}^2 \text{ mol}^{-1}\) at 25 °C. The value of \(x\) is (round off to the nearest integer)
Given:

A

164

B

195

C

389

D

467

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16

2023 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2023

E° = 1.10 V for the following cell reaction:
\(\text{Zn(s)} + \text{Cu}^{2+}(\text{aq}) \rightleftharpoons \text{Zn}^{2+}(\text{aq}) + \text{Cu(s)}\)
For this reaction, the equilibrium constant is \(y \times 10^{37}\) at 298 K. The value of \(y\) is _____ (rounded off to two decimal places).
(Given: \(F = 96485\ \text{C mol}^{-1}\), \(R = 8.314\ \text{J K}^{-1}\text{mol}^{-1}\))

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17

2025 · Life Sciences · Electrochemistry · Conductance and Electrochemical Cells

Life Sciences (XL) 2025

The standard potentials (\(E^0\)) for the Fe³⁺/Fe and Fe³⁺/Fe²⁺ couples are –0.04 V and +0.76 V, respectively.
Given: Faraday constant = 96500 C mol⁻¹.
The value for \(E^0(Fe^{2+}/Fe)\), in V, is __________. (rounded off to two decimal places)

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