Electrochemistry Test

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Electrochemistry Test - 5

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following is mostly used as a reference electrode?

A
ZnCl₂

B
CuSO₄

C
Na₂SO₃

D
Hg₂Cl₂

Solution

The reference electrode is made by using Hg₂Cl₂.
Question 2
1 / -0

During the measurement of EMF of a half cell using a reference electrode and a salt bridge, if the salt bridge is removed, then the voltage

A
remains unchanged

B
decreases to half the previous value

C
increases to its maximum value

D
drops to zero or becomes negative

Solution

A salt bridge, in electrochemistry, is a laboratory device used to connect the oxidation and reduction half-cells of a galvanic cell. It maintains electrical neutrality within the internal circuit, preventing the cell from rapidly running its reaction to equilibrium. If no salt bridge were present, the solution in one half cell would accumulate negative charge and the solution in the other half cell would accumulate positive charge as the reaction proceeded, quickly preventing further reaction, and hence production of electricity.

Hence, during the measurement of EMF of a half cell using a reference electrode and a salt bridge, if the salt bridge is removed, then the voltage drops to zero or becomes negative.

Question 3

1 / -0

Match Column–I with Column–II and indicate your answer by selecting the appropriate option.

Column–I	Column–II
(A) Standard hydrogen electrode	(a) Chemical equivalent/Faraday
(B) Electrochemical equivalent	(b) ΔG^o < 0
(C) E⁰ > 0	(c) Calibration of potentiometer
(D) Weston cadmium cell	(d) E⁰ = 0 at all temperatures

(A) – (d), (B) – (a), (C) – (b), (D) – (c)

(A) – (a), (B) – (d), (C) – (b), (D) – (c)

(A) – (d), (B) – (a), (C) – (c), (D) – (b)

(A) – (c), (B) – (a), (C) – (b), (D) – (d)

Solution

(A) Standard hydrogen electrode has E⁰ = 0 at all temperatures.
So, (A) – (d)
(B) Electrochemical equivalent = Chemical equivalent/Faraday
So, (B) – (a)
(C) E⁰ > 0 corresponds to ΔG⁰ < 0 as both indicate spontaneity of a cell reaction.
So, (C) – (b)
(D) Weston cadmium cell is a standard cell used to calibrate a potentiometer.
So, (D) – (c)
Answer: (A) – (d), (B) – (a), (C) – (b), (D) – (c)

Question 4
1 / -0

An electrochemical cell is represented as follows.

Pt (H₂, 1 atm) | 0.1 M HCl || 0.1 M acetic acid | (H₂, 1 atm) Pt

The emf of this cell will not be zero because the

A
pH values of 0.1 M HCl and 0.1 M acetic acid are not the same

B
acids used in two compartments are different

C
emf of a cell depends on the molarities of acids used

D
temperature is constant

Solution

The emf of this cell will not be zero because the pH values of 0.1 M HCl and 0.1 M acetic acid are not the same.
Question 5
1 / -0

Nernst equation E = E^o - (RT/nF) lnQ indicates that the equilibrium constant K_c will be equal to Q when

A
E = E^o

B
RT/nF = 1

C
E = zero

D
E^o = 1

Solution

Nernst equation E = E^o - (RT/nF) lnQ
At equilibrium: K_c = Q
E = 0
Therefore, E^o = (RT/nF)lnK_c

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Electrochemistry Test - 5

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Electrochemistry Test - 5

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Question 1

ZnCl2

CuSO4

Na2SO3

Hg2Cl2

Solution

Question 2

remains unchanged

decreases to half the previous value

increases to its maximum value

drops to zero or becomes negative

Solution

Question 3

(A) – (d), (B) – (a), (C) – (b), (D) – (c)

(A) – (a), (B) – (d), (C) – (b), (D) – (c)

(A) – (d), (B) – (a), (C) – (c), (D) – (b)

(A) – (c), (B) – (a), (C) – (b), (D) – (d)

Solution

Question 4

pH values of 0.1 M HCl and 0.1 M acetic acid are not the same

acids used in two compartments are different

emf of a cell depends on the molarities of acids used

temperature is constant

Solution

Question 5

E = Eo

RT/nF = 1

E = zero

Eo = 1

Solution

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ZnCl₂

CuSO₄

Na₂SO₃

Hg₂Cl₂

E = E^o

E^o = 1