A current of `1 A` is possed through a dilute solution of sulphuric acid for some time to liberate `1 g` of oxygen. How much hydrogen is liberated during this period? How long was the current passed? Faraday constant `= 96500 C mol^(-1)`.

Explanation

The relative atomic mass of oxygen `= 16` and its `valency = 2` so that the chemical equivalent `E = 16/2 = 8`.
Chemical equivalent of hydrogen `=1`
`m_(oxygen)/m_(hydrogen) = E_(oxygen)/E_(hydrogen) = 8/1`
or, `m_(hydrogen/8 = 1g/8 = 0.125 g`.
We have, `1 g` of oxygen `= 1/8` gram-equivalent.
The charge needed to liberate `1/8` gram-equivalent
`= 1/8` faraday
`=96500/8 C ~= 1.12 xx 10^4 C`.
As the current is `1 A`, the time taken is
`t = Q/i = (1.2 xx 10^4 C)/(1 A)`
`= 1.2 xx 10^4 s`
`= 3 hours 20 minutes`