Question

When an electric current is passed through acidified water, $112\, mL$ of hydrogen gas at N.T.P. was collected at the cathode in $965$ seconds. The current passed, in ampere, is :

• A. 1
• B. 0.5
• C. 0.1
• D. 2

Answer 1

Answer: (A)

1

Answer 2

At cathode: $2 H ^{+}( aq )+2 e^{-} \rightarrow H _{2}( g )$

At NTP, $22.4\, L$ or $22400\, mL$ of $H _{2}=1\, mol$ of $H _{2}$
$112\, mL$ of $H _{2}=\frac{1}{22400} \times 112=0.005\, mol$ of $H _{2}$

We know $n =\frac{I \times t}{F}$
$0.005 =\frac{I \times 965}{2 \times 96500} \Rightarrow I=1\, A$