Question

Which of the following is TRUE for Hydrogen-oxygen fuel cell?

• A. Conc. KOH or NaOH is placed between the electrodes to act as the 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. $Noneofthese$

Answer 1

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

The correct options are
A Conc. KOH or NaOH is placed between the electrodes to act as the 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:

$O_2\left(g\right)+2H_{2}O\left(l\right)+4e^{-}\to 4O{H}^{-}\left(aq\right)$
The fuel cell which we are talking about here is the cell which was used in Apollo space Programme.
It was also a drinking water source for astronauts.
It is $H_2-O_2$ fuel cell.
It consists of porous carbon electrodes containing suitable catalysts (finely divided Pt or Pd) incorporated in them for increasing the rate of electrode reactions. 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. 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:
$\underset{–}{}2H_2\left(g\right)+O_2\left(g\right)\to 2H_{2}O\left(l\right)\underset{–}{}$