Read the following passage and answer the next five questions based on it.
Battery or cell converts chemical energy of the redox reaction to electrical energy. In fuel cell (a galvanic cell), the chemical energy of combustion of fuels like H2, ethanol, etc. are directly converted to electrical energy. In a fuel cell, H2 and O2 react to produce electricity, where H2 gas is oxidised at anode and oxygen is reduced at cathode and the reactions involved are
Anode reaction : H2 + 2OH− → 2H2O + 2e−
Cathode reaction : O2 + 2H2O + 4e− → 4OH−
67.2 L of H2 at STP reacts in 15 minutes.
The source of electrical energy on the Apollo moon flight was :
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → H2-O2 Fuel cell
A fuel cell is a galvanic cell that converts the energy of combustion of a fuel such as hydrogen directly into electrical energy, as long as the reactants are supplied. In the hydrogen–oxygen fuel cell, hydrogen and oxygen are bubbled through porous carbon electrodes into concentrated aqueous NaOH:
\( \displaystyle \text{Cathode: }\ce{O2(g) + 2H2O(l) + 4e^- -> 4OH^-(aq)} \)
\( \displaystyle \text{Anode: }\ce{2H2(g) + 4OH^-(aq) -> 4H2O(l) + 4e^-} \)
\( \displaystyle \text{Cell reaction: }\ce{2H2(g) + O2(g) -> 2H2O(l)} \)
This cell supplied the electrical power in the Apollo space programme.
NCERT (2026-27 edition):
Fuel Cells – …
