Engineering Questions with Answers - Multiple Choice Questions

Chemical Industry MCQ’s – Inorganic Chemical – Fuel Cells

1 - Question

Which of the following reaction takes place at anode in hydrogen-oxygen fuel cell?
a) H2+12O2→H2O
b) H2O→H2+O2
c) H2+2OH−→2H2O+2e−
d) O2+H2O+2e−→HO−2+OH−

Explanation: H2+12O2→H2O is an overall reaction whereas H2O→H2+O2 is an unbalanced reaction. O2+H2O+2e−→HO−2+OH− is a reduction reaction which takes place at cathode, and H2+2OH−→2H2O+2e− is the anodic reaction (oxidation reaction).

2 - Question

The reversible efficiency of a fuel cell is given by _________________
a) ΔGΔH
b) ΔHΔG
c) 1−TΔSΔG
d) 1−TΔGΔH

Explanation: Efficiency of a fuel cell is conversion of ∆H to ∆G(useful electrical energy), hence the ideal or reversible efficiency is given by ƞr=ΔGΔH=1−TΔSΔH.

3 - Question

What is the efficiency of Carnot cycle (where T1 is source temperature and T2 is sink temperature)?
a) (T1−T2)T2
b) (T2−T1)T1
c) (T1−T2)T1
d) (T2−T1)T2

Explanation: The efficiency of an ideal Carnot cycle is given by (1−T2)T2, where T1 is high temperature reservoir and T2 is low temperature reservoir.

4 - Question

What is the overall efficiency of a fuel cell? (E=Delivered voltage, I=current delivered for a period of time T)
a) (EIT)ΔH
b) (ET)ΔHI
c) 1−((EIT)ΔH)
d) ΔHEIT

Explanation: The overall efficiency of a fuel cell is given by ƞo=EITΔH. It is the fraction of heat reaction of primary fuel converted into useful electric work at the device terminals.

5 - Question

Which of the following statement is true regarding efficiencies of fuel cell?
a) ƞ0 = ƞr
b) ƞ0 > ƞr
c) ƞ0 < ƞr
d) ƞ0 ≤ ƞr
Explanation: ƞ0 < ƞr. ƞ0 is the overall efficiency of the fuel cell which includes incorrect ∆H at the electrodes, I2 R losses from cell resistances and polarizability. Hence overall efficiency is always less than the reversible or ideal efficiency.

6 - Question

Which electrolyte is used in a high-temperature fuel cell using coal?
a) MgCO3
b) Fused K2CO3
c) CaCO3
d) Fused Na2CO3
Explanation: Fused K2CO3 is used as electrolyte in high temperature fuel cell using coal. Coal volatiles are sent into a high temperature fused K2CO3 electrolyte fuel cell from retort.

7 - Question

Which of the following reaction takes place at cathode in high temperature fuel cell using coal?
a) 12 O2+ CO2+ 2e– →CO3-2
b) C+2CO3-2 →3CO2+ 4e–
c) CO+CO3-2 →2CO2+ 2e–
d) H2+ CO3-2 → H2 O+CO2+ 2e–
Explanation: 12 O2+ CO2+ 2e– →CO3-2 being reduction reaction takes place at cathode. C+2CO3-2 →3CO2+ 4e– Is an anodic reaction for CH4, CO+CO3-2 → 2CO2+ 2e– is an anodic reaction for CO and H2+ CO3-2 → H2 O+CO2+ 2e– is an anodic reaction for H2.

8 - Question

Gas under high equivalent temperature gas systems is termed as ________________
a) Compressed gas
b) Dissolved gas
c) Liquefied gas
d) Plasma