Question

An electric current of $100$ ampere is passed through a molten liquid of sodium chloride between platinum electrodes for 5 hours. Calculate the volume of chlorine gas liberated at the electrode at NTP.
[Molar mass of $C{l}_2$ is $71g/mol$]

• A. $209L$
• B. $420.7L$
• C. $22.4L$
• D. $310L$

Answer 1

The correct option is A $209L$

When the molten $NaCl$ is electrolysed with platinum electrode, the $N{a}^{+}$ ions get reduced to $Na$ at cathode and $C{l}^{-}$ ions get oxidised to $C{l}_2$ and liberated at anode.

The reaction taking place at anode is :
$2C{l}^{-}\left(l\right)\to C{l}_2\left(g\right)+2e^{-}$
$Q=I\times t=100\times 5\times 60\times 60\text{coulombs}$
By Faradays first law,
$W=\frac{E}{96500}\times Q$
where,
E: Equivalent weight
W: Mass deposited or liberated
Q: Amount of charge passed

The amount of chloride liberated by passing $100\times 5\times 60\times 60$ coulomb of electric charge is,

$W=\frac{71}{2\times 96500}\times 100\times 5\times 60\times 60=662.1g$

Volume of $C{l}_2$ liberated at NTP is,
$=\frac{662.1}{71}\times 22.4\approx 209L$