Question

A sodium sulfate solution was electrolyzed using inert Pt electrodes. The cathode reaction was: 2 H2 0  +  2 e -  →  H2  + 2 OH-. If a current of 3.0 amp was used for 30 min, what weight of H2 gas would be produced? 

Answer 1

Given, Current $i=3Amp.$

Time $t=30min=30\times 60=1800s$

Cathode Reaction:

$2H_2O+2e^-\rightarrow H_2+2OH^-$

Then Amount of charge passes $Q=I\times t=3\times 1800$ columbs.

The amount of chlorine liberated by passing $3\times 1800$ coulomb of electric charge.  $=\dfrac{2}{2\times 96500}\times3\times 1800=0.05595 mole$

Volume of $H_2$  liberated at NTP $= 0.05595\times 22.4 = 1.2534 L$