A fuel cell can be constructed that uses the following two half-reactions.
CO₂(g) + 6H⁺(aq) + 6e– => CH₃OH(aq) + H₂O(l) E^o = + 0.05 V
O₂(g) + 4H⁺(aq) + 4e– => 2H₂O(l) E^o = +1.23 V

Which one of the following would occur at the negative electrode of the cell as it generates electricity?
A. production of H⁺
B. formation of H₂O
C. consumption of CO₂
D. reduction of CH₃OH
Solution
Which one of the following statements about this fuel cell is most likely to be correct?
A. An external power supply is used to recharge the cell.
B. Gaseous products are recycled into the cell to improve efficiency.
C. Chemical energy is not completely converted into electrical energy.
D. More H⁺ ions are produced at the anode than are consumed at the cathode.
Solution

Many reactions occurring in plant and animal cells involve a chemical called nicotinamide adenine dinucleotide, NAD+. One such reaction is
2NADH(aq) + 2H⁺(aq) + O₂(g) <=>2NAD⁺(aq) + 2H₂O(l)
It has been suggested that this reaction could be used in biochemical fuel cells to power pacemakers used to
control irregular heartbeats.
If this reaction were performed in a fuel cell, NADH would
A. undergo oxidation at the anode.
B. undergo reduction at the cathode.
C. undergo reduction at the anode.
D. undergo oxidation at the cathode.
Solution