250+ TOP MCQs on Inorganic Chemical – Fuel Cells and Answers

Chemical Industry Multiple Choice Questions 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^-)

Answer: c
Clarification: (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} )

Answer: a
Clarification: 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} )

Answer: a
Clarification: 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} )

Answer: a
Clarification: 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 = ƞ_r
b) ƞ₀ > ƞ_r
c) ƞ₀ < ƞ_r
d) ƞ₀ ≤ ƞ_r

Answer: c
Clarification: ƞ₀ < ƞ_r. 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

Answer: b
Clarification: 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^–

Answer: a
Clarification: (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

Answer: d
Clarification: 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.