This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Faraday’s Laws of Electrolysis”.

1. According to Faraday’s first law of electrolysis, the amount of any substance deposited at the electrode is directly proportional to the quantity of _______________
a) Voltage drop
b) Resistance
c) Electricity passed
d) Tolerance

Explanation: According to Faraday’s law of electrolysis, the amount of any substance deposited at the electrode is directly proportional to the quantity of electricity passed. It is given by:
m = (Q / F) * (M / Z)
where, m = Mass of the substance liberated at an electrode in grams
Q = Total electric charge passed through the substance in Coulombs
M = Molar mass of the substance in grams per mol
Z = Valency number of ions of the substance
For Faraday’s first law, M, F, and z are constants, so that the larger the value of Q the larger m will be.

2. Electrochemical equivalent may be defined as the ____________ of the substance deposited by the passage of 1 coulomb of electricity.
a) Volume
b) Weight
c) Density
d) Velocity

Explanation: Electrochemical equivalent may be defined as the weight of the substance deposited by the passage of 1 coulomb of electricity. The electrochemical equivalent of an element is measured with a voltameter.

a) 1 coulomb
b) 1000 coulomb
c) 5000 coulomb
d) 96500 coulomb

Explanation: 1 Faraday = 96,500 Coulomb. It is calculated mathematically and is widely used everywhere.

4. According to Faraday’s second law, the weights of different substances evolved by the passage of the same quantity of electricity are proportional to their _______________
a) Chemical equivalent weight
b) Current supply
c) Chemical equivalent density
d) Volume

Explanation: According to Faraday’s second law, the weights of different substances evolved by the passage of same quantity of electricity are proportional to their chemical equivalent weights. For Faraday’s second law, Q, F, and z are constants, so that the larger the value of M/z (equivalent weight) the larger m will be.

5. Silver is electrodeposited on a metallic vessel of surface area 800 cm2 by passing a current of 0.2 A for 3 hours. The thickness of silver deposited is ____________
a) 0.1 mm
b) 0.02 mm
c) 0.05 mm
d) 0.2 mm

Explanation: The thickness of silver deposited is 0.0288 mm. It is calculated mathematically.
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6. The velocity with which an ion moves under a potential gradient of __________ volt/cm in a solution is called ionic mobility.
a) 5
b) 4
c) 3
d) 1

Explanation: The velocity with which an ion moves under a potential gradient of one volt/cm in a solution is called ionic mobility. The separation of ions according to their mobility in the gas phase is called ion mobility spectrometry, in liquid phase, it is called electrophoresis.

7. The unit of ionic mobility in SI system is ____________
a) msV-1
b) m3sV2
c) m2s-1V-1
d) m2s-1V

Explanation: The unit of ionic mobility in SI system is m2s-1V-1. The separation of ions according to their mobility in gas phase is called ion mobility spectrometry, in liquid phase it is called electrophoresis.

8. Which of the following factor does not affect ionic mobility?
a) Pressure
b) Nature of ions
c) Temperature
d) Concentration of the solution

Explanation: The factors which affect the ionic mobility are- nature of the ions, concentration of the solution, temperature and the applied potential difference. It does not get affected by pressure.

9. Faraday constant is the amount of electricity present in 100 moles of electrons.
a) True
b) False

Explanation: Faraday constant is the amount of electricity present in 1 mole of electrons. It is equal to 96500 C mol-1.

10. The molecular formula of cryolite is ____________
a) Al2O3
b) Fe2O3
c) Na3AlF6
d) Na3MgI6

Explanation: The molecular formula of cryolite is Na3AlF6. Cryolite is used as an insecticide and a pesticide. It is also used to give fireworks a yellow color.

11. Refined bauxite is dissolved in molten cryolite at a temperature slightly below ____________
a) 00C
b) 1000C
c) 20000C
d) 10000C

Explanation: Refined bauxite is dissolved in molten cryolite at a temperature slightly below 10000C. Cryolite is used as an insecticide and a pesticide. It is also used to give fireworks a yellow color.

12. Aluminium and its alloys can be given shapes of pipes, tubes, rods, wires, plates or foils.
a) True
b) False

Explanation: Aluminium and its alloys can be given shapes of pipes, tubes, rods, wires, plates or foils. Aluminium is one of the most widely used element. The main alloying agents of aluminium are copper, zinc, magnesium, manganese, and silicon

Sanfoundry Global Education & Learning Series – Engineering Chemistry.

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