Question

In a fuel cell, $H_2$ and $O_2$ react to produce electricity. In the process $H_2$ gas is oxidised at the anode and $O_2$ is reduced at the cathode. If $67.2L$ of $H_2$ at $STP$ reacts in $15min$, what is the average currecnt produced? If the entire current is used for electro deposition of $Cu$ from $C{u}^{2+}$, how many grams of $Cu$ are deposited?

• A. $i=443.3A,M_{Cu}=190.5g$
• B. $i=643.3A,M_{Cu}=190.5g$
• C. $i=643.3A,M_{Cu}=180.5g$
• D. $i=543.3A,M_{cu}=190.5g$

Answer 1

The correct option is B $i=643.3A,M_{Cu}=190.5g$

Reaction at the anode of fuel cell,

$\underset{1mol22.4L}{H_2\left(g\right)}\to \underset{2mol2F}{2H^{+}}+2e^{-}$

$22.4L\text{of}{H}_2\text{correspond}=2\times 96500C$
$67.2L\text{of}{H}_2\text{correspond}=\frac{2\times 96500}{22.4}\times 67.2C$

$\text{Time}=15\times 60s$

$\text{Average current}=\frac{\text{Charge}}{\text{Time}}$
$\text{Average current}=\frac{2\times 96500\times 67.2}{22.4\times 15\times 60}=643.3A$

$\text{Mass of copper deposited}=\frac{\text{Equivalent weight}}{96500}\times \text{Charge}$
$\text{Mass of copper deposited by}\frac{2\times 96500}{22.4}\times 67.2C=\frac{63.5}{2\times 96500}\times \frac{2\times 96500\times 67.2}{22.4}=190.5g$