Question

An electrolytic cell is constructed for preparing hydrogen. For an average current of 1 ampere in the circuit, the time required to produced $450mL$ of hydrogen at NTP is approximately.

• A. 30 min
• B. 1 hour
• C. 2 hours
• D. 5 hours

Answer 1

The correct option is B 1 hour

At NTP, 1 mole of $H_2=22400mL$
$450mL$ of $H_2$ at NTP $=\frac{450mL}{22400L/mol}=0.02mol$
$2H^{+}+2e^{-}\to H_2$
Number of moles of electrons $=2\times$ number of moles of $H_2=2\times 0.02=0.04mol$

Number of moles of electrons

$=\frac{I\left(A\right)\times t\left(s\right)}{96500C/mol{e}^{-}}$

$0.04mol=\frac{1A\times t\left(s\right)}{96500C/mol{e}^{-}}$

$t=3877s$
Convert unit from seconds to minutes

$t=\frac{3877s}{60s/min}=65min$

Convert unit from minutes to hours

$t=\frac{65min}{60min/hr}=1.07hr\simeq 1hr$

Hence, approximately 1 hour is required.