Question

A current of $9.65$ amp is passed through an aqueous solution of $NaCl$ using suitable electrodes for $1000s$. Given that $1$ faraday equals $96500$ coulombs the amount of $NaOH\left( {mol.wt.40.00} \right)$ formed on electrolysis is:
A.$2.0g$
B.$8.0g$
C.$4.0g$
D.$1.0g$

Answer 1

The scientist Faraday discovered some laws. In that the faraday’s first law will be useful to calculate the amount of substance deposited or formed on electrolysis from the electrochemical equivalent mass of the substance, amount of current in amperes and time in seconds.
Formula used:
$m = Z \times i \times t$
Where $m$ is amount of sodium hydroxide formed on electrolysis
$i$ is amount of current in amperes
$Z$ is electrochemical equivalent mass of the substance
$t$ is time in seconds

Complete answer:
Given that a current of $9.65$ is passed through an aqueous solution of sodium chloride solution using suitable electrodes for $1000s$.
But, one faraday is equals to $96500$ coulombs
The electrochemical equivalent mass of the substance $Z$ will be $\dfrac{E}{{96500}} = \dfrac{{40}}{{96500}}$
The equivalent weight of sodium hydroxide $E$ is $40$
The current is $9.65$ amp
$t$ is time in seconds is $1000s$
Substitute the values in the above formula, we will get
$m = \dfrac{{40}}{{96500}} \times 9.65 \times 1000$
By further simplification the amount of sodium hydroxide formed on electrolysis will be $4gm$
Thus, when a current of $9.65$ amp is passed through an aqueous solution of $NaCl$ using suitable electrodes for $1000s$ the amount of sodium hydroxide formed on electrolysis will be $4gm$
Hence, option (C) is the correct answer.

Note:
The electrochemical equivalent mass of the substance is the ratio of the equivalent weight and the charge in coulombs. The equivalent weight of sodium hydroxide is equal to the molecular weight of sodium hydroxide as the basicity of sodium hydroxide is one.