Question

Peroxy disulphuric acid `(H_(2)S_(2)O_(8))` can be prepared by electrolytic oxidation of `H_(2)SO_(4)` as :
`2H_(2)SO_(4) rarr H_(2)S_(2)O_(8)+2H^(+)+2e^(-)`
Oxygen and hydrogen are by products. In such an electrolysis 9.72 litre of `H_(2)` and 2.35 litre of `O_(2)` were generated at NTP. What is the mass of peroxy disulphuric acid formed ?

Answer 1

Anodic reaction : `2H_(2)SO_(4) rarr H_(2)S_(2)O_(8)+2H^(+) +2e^(-)`
`2H_(2)O rarr 4H^(+)+O_(2)+2e^(-)`
Cathodic reaction : `2H_(2)O+2e^(-) rarr 2OH^(-) +H_(2)`
Total equivalent of `H_(2)S_(2)O_(8)`+ equivalent of oxygen = Equivalent of `H_(2)`
9.72 litre `H_(2)=9.72/11.2=0.868` equivalent
2.35 litre `O_(2)=2.35/5.6=0.42` equivalent
Equivalent of `H_(2)S_(2)O_(8)=(0.868-0.420)`
`=0.448`
Mass of `H_(2)S_(2)O_(8)=0.448xx194/2=43.456 g`