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 quantity of electricity produced in the oxidation of 67.2 L of H2 at STP is :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 579000 C
The charge carried by one mole of electrons is one faraday, about 96500 C. So the quantity of electricity is the number of moles of electrons multiplied by F.
From the anode reaction, each mole of \( \ce{H2} \) releases 2 moles of electrons:
\( \displaystyle \ce{H2 + 2OH^- -> 2H2O + 2e^-} \)
67.2 L of hydrogen at STP is 67.2 / 22.4 = 3 mol, which gives 3 × 2 = 6 mol of electrons:
\( \displaystyle Q=n(e^-)\times F=6\times96500\ \mathrm{C}=579000\ \mathrm{C} \)
So the quantity of electricity produced is 579000 C (6 F).