Question

Which of the following is/are TRUE for Hydrogen-oxygen fuel cells?

• A. Conc. KOH or NaOH is placed between the electrodes to act as an electrolyte
• B. At anode :
  $2H_2\left(g\right)+4O{H}^{-}\left(aq\right)\to 4H_{2}O\left(l\right)+4e^{-}$
• C. At cathode:
  $O_2\left(g\right)+2H_{2}O\left(l\right)+4e^{-}\to 4O{H}^{-}\left(aq\right)$
• D. None of these

Answer 1

Answer: (A), (B), (C)

At cathode:

$O_2\left(g\right)+2H_{2}O\left(l\right)+4e^{-}\to 4O{H}^{-}\left(aq\right)$
Concentrated KOH or NaOH solution is placed between the electrodes to act as the electrolyte. Hydrogen and oxygen gases are bubbled through the porous electrodes into the KOH/ NaOH solution. The following electrode reactions take place:
At anode:$2H_2\left(g\right)+4O{H}^{\ominus }\left(aq\right)\to 4H_{2}O\left(l\right)+4e^{-}$
At cathode: $O_2\left(g\right)+2H_{2}O\left(l\right)+4e^{-}\to 4O{H}^{\ominus }\left(aq\right)$
Overall reaction:
$\underset{–}{}2H_2\left(g\right)+O_2\left(g\right)\to 2H_{2}O\left(l\right)\underset{–}{}$