This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Electrochemistry – Galvanic Cells”.
1. A galvanic cell converts electrical energy into chemical energy.
a) True
b) False
View Answer
Explanation: A galvanic cell is a type of electrochemical cell that converts chemical energy into electrical energy. The electrochemical cell which converts electrical energy into chemical energy is called electrolytic cell.
2. Who invented the galvanic cell?
a) Galvani and Volta
b) Henry Cavendish
c) Joseph Priestley
d) Antoine Lavoisier
View Answer
Explanation: Electrochemical cells are also called galvanic or voltaic cells, after the names of Luigi Galvani and Alessandro Volta who were the first to perform experiments on the conversion of chemical energy into electrical energy.
3. Which of the following electrolytes is not preferred in a salt bridge?
a) KCl
b) KNO3
c) NH4NO3
d) NaCl
View Answer
Explanation: In a salt bridge, the electrolytes like KCl, KNO3 or NH4NO3 are preferred because their ions have almost equal transport number, viz., 0.5, i.e., they move with almost the same speed when an electric current flows through them.
4. Which of the following is false regarding galvanic cells?
a) It converts chemical energy into electrical energy
b) The electrolytes taken in the two beakers are different
c) The reactions taking place are non-spontaneous
d) To set up this cell, a salt bridge is used
View Answer
Explanation: Galvanic cells are used to convert chemical energy into electrical energy. Two electrodes are usually set up in two separate beakers. The electrolytes taken in the two beakers are different. Galvanic cells are based upon spontaneous redox reactions. A salt bridge is used to set up this cell.
5. The electrode on which oxidation occurs is called the anode. True or False?
a) True
b) False
View Answer
Explanation: An anode is an electrode where oxidation takes place. An anode is a negative pole in a galvanic cell. In an electrolytic cell, the anode acts as the positive pole. Cathodes are electrodes where reduction takes place.
6. A cell is prepared by dipping a copper rod in 1 M CuSO4 solution and an iron rod in 2 M FeSO4 solution. What are the cathode and anode respectively?
a) Cathode: Iron, Anode: Copper
b) Cathode: Copper, Anode: Iron
c) Cathode: Iron, Anode: Iron
d) Cathode: Copper, Anode: Copper
View Answer
Explanation: The given cell is represented as:
Fe (s) | FeSO4 (2 M) || CuSO4 (1 M) | Cu (s)
Since the E° of iron < E° of copper, copper rod acts as the cathode and iron rod acts as the anode.
7. Which of the following is the correct order of reactivity of metals?
a) Zn > Mg > Fe > Cu > Ag
b) Zn > Mg > Fe > Ag > Cu
c) Mg > Zn > Fe > Ag > Cu
d) Mg > Zn > Fe > Cu > Ag
View Answer
Explanation: Greater the oxidation potential of metal, the more easily it can lose electrons and hence greater is its reactivity. As a result, a metal with greater oxidation potential can displace metals with lower oxidation potentials from their salt solutions. Hence, the correct order of reactivity is Mg > Zn > Fe > Cu > Ag.
8. Which of the following is a correct method to calculate the EMF of a galvanic cell?
a) Standard EMF of the cell = [Standard reduction potential of the reduction half reaction] + [Standard reduction potential of the oxidation half reaction]
b) Standard EMF of the cell = [Standard oxidation potential of the oxidation half reaction] – [Standard reduction potential of the reduction half reaction]
c) E°cell = E°cathode – E°anode
d) Standard EMF of the cell = [Standard reduction potential of the right hand side electrode] + [Standard reduction potential of the left hand side electrode]
View Answer
Explanation: The correct methods to calculate the EMF of a galvanic cell are:
Standard EMF of the cell = [Standard reduction potential of the reduction half reaction] – [Standard reduction potential of the oxidation half reaction].
Standard EMF of the cell = [Standard oxidation potential of the oxidation half reaction] + [Standard reduction potential of the reduction half reaction].
E°cell = E°cathode – E°anode.
Standard EMF of the cell = [Standard reduction potential of the right hand side electrode] – [Standard reduction potential of the left hand side electrode].
9. What is the EMF of a galvanic cell if E°cathode = 0.80 volts and E°anode = -0.76 volts?
a) 1.56 volts
b) 0.04 volts
c) -1.56 volts
d) -0.04 volts
View Answer
Explanation: Given,
E°cathode = 0.80 volts
E°anode = -0.76 volts
E°cell = E°cathode – E°anode
E°cell = 0.80 – (-0.76)
E°cell = 1.56 volts.
10. What is the EMF of a galvanic cell if the standard oxidation potential of the oxidation half-reaction is 0.64 volts and the standard reduction potential of the reduction half-reaction is 0.48 volts?
a) 1.48 volts
b) 1.12 volts
c) 1.36 volts
d) 0.96 volts
View Answer
Explanation: Given,
Standard oxidation potential of the oxidation half reaction = 0.64 volts
Standard reduction potential of the reduction half reaction = 0.48 volts
Standard EMF of the cell = [Standard oxidation potential of the oxidation half reaction] + [Standard reduction potential of the reduction half reaction]
= 0.64 + 0.48
= 1.12 volts.
11. What is the EMF of a galvanic cell if the standard reduction potential of the reduction half-reaction is -0.38 volts and the standard reduction potential of the oxidation half-reaction is 0.52 volts?
a) -0.9 volts
b) -0.6 volts
c) 0.9 volts
d) 0.6 volts
View Answer
Explanation: Given,
Standard reduction potential of the reduction half reaction = -0.38 volts
Standard reduction potential of the oxidation half reaction = 0.52 volts
Standard EMF of the cell = [Standard reduction potential of the reduction half reaction] – [Standard reduction potential of the oxidation half reaction]
= -0.38 – (0.52)
= -0.9 volts.
12. What is the standard reduction potential of the cathode of a galvanic cell if the standard EMF of the cell and the standard reduction potential of the anode are 2.71 and -2.37 respectively?
a) 0.68 volts
b) -0.68 volts
c) -0.34 volts
d) 0.34 volts
View Answer
Explanation: Given,
Standard EMF of the cell = E°cell = 2.71 volts
Standard reduction potential of the anode = E°anode = -2.37 volts
E°cell = E°cathode – E°anode
E°cathode = E°cell + E°anode
= 2.71 + (-2.37)
= 0.34 volts.
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