Question

The mass of copper that will be deposited at cathode in electrolysis of 0.2 molar solution of copper sulphate with a quantity of electricity equal to that required to liberate 2.24 litre of hydrogen from 0.1 molar aqueous h2 s o4 is past will be

Answer 1

Molar gas volume at stp = 22.4 liters

The moles of hydrogen Gas deposited from Sulphuric acid is :

2.24/22.4 = 0.1 moles

1 Faraday = 96500 C

For hydrogen gas to be deposited 2 electrons are required hence :

1 mole of hydrogen gas requires:

96500 × 2 = 193000 C

1 mole = 193000 C

0.1 moles =?

0.1 × 193000 = 19300 C

For copper to be deposited we need 2 electrons therefore :

1 mole = 96500 × 2 = 193000

The moles deposited by 19300 C will be :

19300/193000 = 0.1 moles

Molar mass of copper = 64

Mass deposited = 64 × 0.1 = 6.4 grams