This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Electroplating Equipment and Operating Conditions”.
1. Identify the correct conditions for electroplating to take place (in K and in ATM).
a) T=200 and P=20
b) T=300 and P=25
c) T=100 and P=60
d) T=110 and P=30
Explanation: For electroplating to take place, the temperature must be above 0 degree Celsius (that is above 273 kelvin) and the pressure must be atmospheric pressure. Thus the suitable temperature from the above options are T=300 and P=25.
2. Which of the following is wrong about the working conditions of electroplating?
a) Temperature follows a steady state
b) Pressure follows a steady state
c) Pressure is compressed
d) Pressure is neglected
Explanation: If a graph between temperature and pressure is drawn, then it is seen that temperature gives a straight line (that is pressure and temperature are directly proportional). Thus temperature is maintained at steady state.
3. If the temperature of cadmium bath is maintained at 400 K and the concentration of cadmium is 70 g, calculate the pressure at that temperature (given, the gas constant is 8.314 J /mol. • K).
Explanation: According to Falton’s formula P=TR/C, where T is the temperature, R is the gas constant, C is the concentration. So, here P = 400 x 8.314/70 = 47.50.
4. If the pressure of mercury bath is maintained at 30 ATM and the concentration of mercury is 89 g, calculate the temperature at that pressure (given, the gas constant is 8.314 J/mol. • K).
Explanation: According to Falton’s formula P=TR/C, where T is the temperature, R is the gas constant, C is the concentration. Therefore T=PC/R. So, here T=30 x 89/8.314 = 312.4.
5. What will happen if the electroplating conditions are exceeded in a system?
a) The process will come to halt
b) Excess metal deposition will take place
c) Electrolyte leakage will take place
d) Impurities will not be removed
Explanation: When electroplating has to continue in a steady state, the conditions of temperature and pressure has to be satisfied. If the conditions exceed the normal conditions then the process comes to halt.
6. What should be the minimum amount of current that has to be passed to get leakage free metal.
a) 240 A
b) 200 A
c) 350 A
d) 100 A
Explanation: Though the amount of current depends on the metal that is used, the minimum amount of current required for all metals that are discovered is 100 A.
7. Where does pure metal gets deposited after passing current?
d) Negative pole
Explanation: During electroplating, impure metal is kept as anode and electrolyte is the metal salt solution. After the current has passed, the electrons will pass through the electrolyte and hence we will get the pure metal at anode.
8. What is the cause of the formation of the depletion layer?
a) Deletion in charge carriers
b) Leakage current
c) Deposition of extra layer on pure metal
d) Extra depletion
Explanation: When electroplating takes place, there is a value called the critical concentration where the amount of deposition is controlled by the passage of current. When this concentration exceeds, we get a depletion layer.
9. Calculate the concentration of the metal formed from the given data.
Explanation: According to Falton’s formula P=TR/C, where T is the temperature, R is the gas constant, C is the concentration. Therefore C = TR/P. So, here T = 340 x 8.314/ 120 = 23.56.
10. Using which formula is concentration calculated?
a) Falton method
b) Thomson method
c) Robert method
d) Lewis method
Explanation: Electroplating method was started in 1880 by Falton. He was the first to give the law for calculating the amount of concentration during electroplating. According to his law P=TR/C.
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