Answer to Question #156304 in General Chemistry for Tayyaba riaz

Question

How much electrical energy is required to generate 1.000L of H, at 25°C and 1.00 atm pressure by the electrolysis of water?

Answer 1

Redox reactions in water electrolysis :

Anode: 2H₂O (l) = O₂ (g) + 4H⁺ (aq) + 4e^-

Cathode: 4H₂O (l) + 4e^- = 2H₂ (g) + 4OH^- (aq)

Reaction: 2H₂O = 2H₂ (g) + O₂ (g)

mol H₂:

n = PV/RT

n = (1.00 atm x 1.000 L)/(0.082 atm•L/mol•K x 298 K)

n = 0.041 mol

From reaction at cathode : mol ratio of electron and H₂ = 4 : 2, so mol electrons :

= 4/2 x mol H₂ = 2 x 0.041 mol = 0.082 mol

1 Faraday is the amount of electricity that is passed in the electrolysis cell to obtain 1 mole of electrons.

1 Faraday = 1 mole of electrons = 96500 Coulombs

So the energy required :

0.082 Faraday