Four moles of electrons were transferred from anode to cathode in an experiment on electrolysis of water. The total volume of the two gases (dry and at STP) produced will be approximately (in litres)

During electrolysis of water

At Cathode  4H⁺ + 4e^- → 2H₂

At Anode     4OH^- → 2H₂O + O₂ + 4e^-

4 moles of electrons = 4 F electricity = 4eq of each gas is liberated.

1 eq of H₂ = 11.2 lit at STP

4 eq of H₂ = 4 x 11.2 lit = 44.8 lit

1 eq of O₂ = 5.6 lit at STP

4 eq of O₂ = 4 x 5.6 lit = 22.4 lit

Total volume of both gases = 44.8 + 22.4 = 67.2 lit.