Electrochemistry - Metallurgical Thermodynamics - Metallurgical Engineering Previous Year Questions

1

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2007

The standard EMF of the cell is

A

-1.17 V

B

-1.21 V

C

-1.36 V

D

+1.56 V

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2

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2007

When the activity of alumina is 0.1, the EMF of this cell is

A

-1.17 V

B

-1.21 V

C

-1.36 V

D

+1.21 V

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3

2009 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2009

The activity of copper in the 'impure copper' is 0.5 at 298 K. The minimum voltage required to refine 'impure copper' to pure copper using an electrolyte having Cu²⁺ ions at 298 K is

A

0.9 mV

B

9 mV

C

90 mV

D

900 mV

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4

2010 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2010

The difference in reversible potential between oxygen reduction reaction and hydrogen evolution reaction at any pH in an aqueous electrolyte is (given standard reduction potentials for hydrogen evolution reaction: \(E^0_{2H^+/H_2} = 0\) V, SHE and oxygen reduction reaction: \(E^0_{O_2/4OH^-} = 0.4\) V, SHE. Also, \(p_{H_2} = p_{O_2} = 1\) atm)

A

0 V

B

0.41 V

C

0.82 V

D

1.23 V

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5

2011 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2011

A metal is electrochemically polarized to a potential which is higher than the standard reduction potential of the metal. The overvoltage will be

A

zero

B

negative

C

positive

D

initially negative, then positive

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6

2011 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2011

Al₂O₃ + 6H⁺ + 6e^- = 3H₂O + 2Al \( \Delta G^0 = 897.3 \) kJ
where, hydrogen ion concentration is unity. The reduction potential of the above reaction under standard state will be

A

-1.55 V

B

-1.40 V

C

1.65 V

D

1.75 V

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7

2013 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2013

For the following electrochemical reaction \( Sn + 2H^+ = Sn^{2+} + H_2 \), if the solution has \( Sn^{2+} \) concentration \( 10^{-2} \) M and pH 5 at 298 K, which of the following is true?
Given: standard reduction potential for \( Sn^{2+} + 2e^- \rightarrow Sn \) is -0.136 V versus SHE; \( p_{H_2} = 1 \) atm

A

Sn undergoes oxidation

B

\(H^+ \) undergoes reduction

C

\(Sn^{2+} \) undergoes reduction

D

No net reaction

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8

2014 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2014

An electrolytic refining cell for copper consists of an alloy with activity of copper \(a_{Cu} = 0.8\) as the anode, and pure copper as the cathode. What is the absolute value of the cell potential (in millivolts) at 25°C, given that copper is divalent? Faraday constant is 96500 C/mol and the universal gas constant is 8.314 J/(mol.K). ______

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9

2017 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2017

For the electrochemical reaction, \(Cu^{2+} + Zn = Zn^{2+} + Cu\) ; the standard cell potential at 25°C and 1 atm pressure is: \n(Given: \(E^o (Cu^{2+}/Cu) = 0.337 V\) and \(E^o (Zn^{2+}/Zn) = -0.763 V\))

A

-0.426 V

B

0.426 V

C

0.55 V

D

1.1 V

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10

2017 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2017

The Pourbaix plot of the reaction Al³⁺ + 2H₂O = AlO₂⁻ + 4H⁺ in potential (E) versus pH diagram is:

A

B

C

D

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11

2017 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2017

A solution contains 10⁻³ M of Fe³⁺ at 25°C. The solubility product of Fe(OH)₃ is 10⁻³⁹. Assuming activity equals concentration, the minimum pH at which Fe³⁺ will precipitate as Fe(OH)₃ is __________ (answer up to two decimal places)

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12

2018 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2018

What is the voltage required to electrolytically refine impure copper of activity a_Cu = 0.9 (Raoultian standard state) to pure copper at 300 K
Given: Gas constant R = 8.314 J mol⁻¹ K⁻¹, and Faraday’s constant F = 96500 C mol⁻¹.

A

1.36 mV

B

2.72 mV

C

0 mV

D

5.44 mV

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13

2020 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2020

Which one of the following processes is an example of an electrolytic cell?

A

Corrosion of a metal rod in ambient atmosphere

B

Charging of a rechargeable battery

C

Discharging of a rechargeable battery

D

Sacrificial cathodic protection system

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14

2020 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2020

A galvanic cell is formed by connecting Zn (E̊_Zn²⁺/Zn = −0.76 V) and Fe (E̊_Fe²⁺/Fe = −0.44 V) wires immersed in their respective ion solutions. The cell discharges spontaneously with a voltage of 0.5 V. The ratio of the concentration of [Fe²⁺] to [Zn²⁺] ions in the cell is of the order of:

A

10⁻⁶

B

10⁻⁵

C

10⁶

D

10⁷

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15

2021 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2021

If \(E^o_{Ni^{2+}/Ni} = -0.25\) V, the value of \(\mu^o_{Ni^{2+}}\) (in J mol\(^{-1}\)) at 298 K is: __________ (round off to nearest integer).
Given: F = 96500 C mol\(^{-1}\)

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16

2022 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2022

The emf of the cell
Au-Pb(liquid) | PbCl₂-KCl(liquid) | Cl₂(gas, 0.5 atm), C(graphite)
is 1.2327 V at 873 K. Activity of Pb in the Au-Pb alloy is 0.72 and the activity of PbCl₂ in the electrolyte is 0.18. The standard Gibbs energy of formation of PbCl₂(liquid) at 873 K is _____ kJ·mol⁻¹ (round off to 1 decimal place).
Given: R = 8.314 J·K⁻¹·mol⁻¹ and F = 96500 C·mol⁻¹.

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17

2023 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2023

In an aqueous solution of \(Fe^{2+}\) ions with concentration of \(10^{-4}\) M at 298 K and atmospheric pressure, the reduction potential of Fe in volt is __________ (round off to 2 decimal places).
Given: Standard reduction potential, \(E^0_{Fe^{2+}/Fe} = -0.44\) V
Faraday's constant, \(F = 96500\) C per mole of electrons
Universal gas constant, \(R = 8.314\) J mol\(^{-1}\)K\(^{-1}\)

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18

2024 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2024

The cupric ion (\( Cu^{2+} \)) concentration in the electrolyte (at \( 298 \, K \)) required to make the potential of pure copper equal to \( 0.17 \, V \) is _____ \( \times 10^{-6} \, gram \cdot mol \cdot (litre)^{-1} \).
(Round off to two decimal places).
Gas constant \( R = 8.314 \, J \cdot mol^{-1} \cdot K^{-1} \)
Faraday's constant \( F = 96500 \, C \cdot mol^{-1} \) (of electrons)
Standard reduction potential of Cu, \( E^o = 0.34 \, V \)

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19

2025 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2025

Consider the following cell reaction:
\( \text{Mg} + \text{Cd}^{2+} \rightleftharpoons \text{Mg}^{2+} + \text{Cd} \)
The standard Gibbs free energy change for the reaction is ______ kJ (rounded off to an integer).
Given: Standard oxidation potentials for the reactions with respect to standard hydrogen electrode are:
\( \text{Mg} \rightleftharpoons \text{Mg}^{2+} + 2e^- \qquad E^\circ = 2.37 \text{ V} \)
\( \text{Cd} \rightleftharpoons \text{Cd}^{2+} + 2e^- \qquad E^\circ = 0.403 \text{ V} \)
Faraday's constant = 96500 C mol⁻¹

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20

2026 · Metallurgical Engineering · Metallurgical Thermodynamics · Electrochemistry

Metallurgical Engineering (MT) 2026

Al₂O₃ can be electrolyzed with an inert anode or a carbon anode.
Overall reactions are as follows:
Reaction I: For inert anode,
2/3 Al₂O₃ (s) → 4/3 Al (l) + O₂ (g) ; ΔG° (in Joules) = 1124800 – 218 T
Reaction II: For carbon anode,
2/3 Al₂O₃ (s) + C (s) → 4/3 Al (l) + CO₂ (g) ; ΔG° (in Joules) = 730700 – 218 T
T denotes temperature in Kelvin
Given: Faraday constant = 96500 Coulomb
If inert anode is replaced by carbon anode during electrolysis of Al₂O₃ at temperature 1300 K, the decrease in the magnitude of decomposition potential between the two reactions (rounded off to two decimal places) is __________ Volts.

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