Question

A dilute aqueous solution of MgSO4 is electrolysed using Pt electrodes. The total charge required for obtaining 1 mol gas at anode is?

Answer 1

Total 386000 Coulomb charge will be required for obtaining 1 mol gas at anode.

It usually requires a large amount of current to produce much oxygen or hydrogen gas.  

For example, how much electrical current would be needed to produce one mole of oxygen gas?  The mass of oxygen is 32 g, and at room temperature and pressure conditions about 24 litres.

Step 1: Balanced equation at the anode

H2O   1/2O2 (g) + 2H+ + 2e-  Oxidation = Anode

It will take 4 moles of electrons to produce 1 mole of oxygen gas.

Step 2: Electrical current is usually measured in amperes.  A current of 1 amp for 1 second is one Coulomb (C) of electrons.  There are approximately 95500 C in a mole of electrons, so our 4 moles of electrons is

4 x 96500 = 386000 C

Total charge= 386000 C