a) Calculate the mass of Li formed by electrolysis of molten LiCl by a current of 8.2 104 A flowing for a period of 14 hr. Assume the electrolytic cell is 70. percent efficient. (b) What is the energy requirement for this electrolysis per mole of Li formed if the applied emf is + 8.4 V? answer in kWh/mol

a) Answer:

= 210,000 gram or 210 Kg

Explanation:

14 hr is equivalent to;

= 14 * 3600 s

But;

8.2x10^4 A = 8.2x10^4 Coulomb / second = 8.2x10^4 C/s

1 Faraday = 96485C

Molar mass of Li: 6.941 g/mol

Therefore;

{ (8.2x10^4 C/s) * (14*3600s) * (6.941 g/mol) / (96485C/mol) }*70%

= 2.1x10^5 gram or 210 kg

b. Answer;

= 0.23 kWh/mol

Explanation and solution;

Energy per mole is given by;

(96485C/mol) * (8.4V) = 8.10x10^5 (J/mol)

= 8.10x10^5 (Ws/mol)

Divide by 3600s/h to get:

= 8.10x10^5 (Ws/mol)

= 225 Wh/mol

= 0.23 kWh/mol