This set of Chemical Industry Multiple Choice Questions & Answers (MCQs) focuses on “Inorganic Chemical – Fuel Cells”.
1. Which of the following reaction takes place at anode in hydrogen-oxygen fuel cell?
a) \(H_2+\frac{1}{2} O_2 \rightarrow H_2 O\)
b) \(H_2 O \rightarrow H_2+ O_2\)
c) \(H_2+2OH^-\rightarrow 2H_2 O+ 2e^-\)
d) \(O_2+H_2 O+ 2e^-\rightarrow HO_2^-+ OH^-\)
View Answer
Explanation: \(H_2+\frac{1}{2} O_2 \rightarrow H_2 O\) is an overall reaction whereas \(H_2 O \rightarrow H_2+ O_2\) is an unbalanced reaction. \(O_2+H_2 O+ 2e^-\rightarrow HO_2^-+ OH^-\) is a reduction reaction which takes place at cathode, and \(H_2+2OH^-\rightarrow 2H_2 O+ 2e^-\) is the anodic reaction (oxidation reaction).
2. The reversible efficiency of a fuel cell is given by _________________
a) \(\frac{∆G}{∆H} \)
b) \(\frac{∆H}{∆G} \)
c) \(1-\frac{T∆S}{∆G} \)
d) \(1-\frac{T∆G}{∆H} \)
View Answer
Explanation: Efficiency of a fuel cell is conversion of ∆H to ∆G(useful electrical energy), hence the ideal or reversible efficiency is given by \(ƞ_r=\frac{∆G}{∆H}=1-\frac{T∆S}{∆H}.\)
3. What is the efficiency of Carnot cycle (where T1 is source temperature and T2 is sink temperature)?
a) \(\frac{(T_1-T_2)}{T_2} \)
b) \(\frac{(T_2-T_1)}{T_1} \)
c) \(\frac{(T_1-T_2)}{T_1} \)
d) \(\frac{(T_2-T_1)}{T_2} \)
View Answer
Explanation: The efficiency of an ideal Carnot cycle is given by \(\frac{(1-T_2)}{T_2},\) where T1 is high temperature reservoir and T2 is low temperature reservoir.
4. What is the overall efficiency of a fuel cell? (E=Delivered voltage, I=current delivered for a period of time T)
a) \(\frac{(EIT)}{∆H} \)
b) \(\frac{(ET)}{∆HI} \)
c) \(1-(\frac{(EIT)}{∆H}) \)
d) \(\frac{∆H}{EIT} \)
View Answer
Explanation: The overall efficiency of a fuel cell is given by \(ƞ_o=\frac{EIT}{∆H}.\) It is the fraction of heat reaction of primary fuel converted into useful electric work at the device terminals.
5. Which of the following statement is true regarding efficiencies of fuel cell?
a) ƞ0 = ƞr
b) ƞ0 > ƞr
c) ƞ0 < ƞr
d) ƞ0 ≤ ƞr
View Answer
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. Which electrolyte is used in a high-temperature fuel cell using coal?
a) MgCO3
b) Fused K2CO3
c) CaCO3
d) Fused Na2CO3
View Answer
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. Which of the following reaction takes place at cathode in high temperature fuel cell using coal?
a) \(\frac{1}{2}\) 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–
View Answer
Explanation: \(\frac{1}{2}\) 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. Gas under high equivalent temperature gas systems is termed as ________________
a) Compressed gas
b) Dissolved gas
c) Liquefied gas
d) Plasma
View Answer
Explanation: Gas under high equivalent temperature gas systems is termed as Plasma. Plasma contains high velocity electrons, anode and cathode material, and ions of the original gaseous media.
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