Question

When an electric current is passed through acidified water, $112ml$ of hydrogen gas at $STP$ collects at the cathode in $965$ seconds. What is the current passed, in ampere?

• A. $1.0$
• B. $0.5$
• C. $0.1$
• D. $2.0$

Answer 1

Answer: (A)

$1.0$

At $STP$, $22.4litres=1moleof{H}_{2}gas=2g$ of $H_2$ gas.

$\therefore$ $112mlof{H}_{2}gascontains\frac{2\times 112}{22.4\times {10}^3}=0.01g$ of $H_2$ gas

Now,

${2H}^{+}+{2e}^{-}\to H_2$

According to Faraday's law,

$nF=1mole$

where, $F=$ Faraday's constant$=96500C$

& $n=numberofelectrons=2$

$\therefore$ $1$ mole deposits $2\times 96500C$

$0.01g$ deposits $\frac{2\times 96500\times 0.01}{2}=965C$

$\therefore$ Current $=\frac{Charge}{Time}=\frac{965}{965}$

$=1Ampere$

Hence, option $\left(A\right)$ is correct.