Question

When $9.65$ampere current was passed for $1.0$ hour into nitrobenzene in an acidic medium, the amount of p-aminophenol produced is ________.
A. ${\text{10}}{\text{.9g}}$
B. ${\text{109}}{\text{.0g}}$
C. ${\text{9}}{\text{.81g}}$
D. ${\text{98}}{\text{.1g}}$

Answer 1

To solve this question, you must recall the formula for Faraday’s first law of electrolysis. It states that, “the amount of any substance that is deposited or liberated at an electrode is directly proportional to the quantity of electricity passing through the electrolytic cell.

Formula used: ${\text{w}} = {\text{ZIt}}$
Where, ${\text{w}}$is the amount of substance liberated or deposited.
${\text{I}}$ is the current passed through the cell
${\text{t}}$ is the time for which current is passed.
And, ${\text{Z}}$is the electrochemical equivalent of a substance
${\text{Z}}$ is given by $\dfrac{{\text{E}}}{{96500}}$
Where ${\text{E}}$ is the equivalent weight of the substance liberated or deposited.
This gives the equation as: ${\text{w}} = \dfrac{{{\text{EIt}}}}{{96500}}$.

Complete step by step solution:
It is given that, $9.65$ ampere current was passed for $1.0$ hour, which is the same as $3600$ seconds.
The reduction of nitrobenzene to para amino phenol requires 4 electrons per molecule of nitrobenzene.
Or we can say that one mole of nitrobenzene requires 4 moles of electrons to be reduced to para amino phenol.
The n-factor of the reaction is 4
Thus, the equivalent weight of para amino phenol is $= \dfrac{{109}}{4}$.
Now, we can find the amount of para amino phenol formed using the equation,
${\text{w}} = \dfrac{{{\text{EIt}}}}{{96500}}$
Substituting the values we get,
${\text{w}} = \dfrac{{\left( {\dfrac{{109}}{4}} \right)\left( {9.65} \right)\left( {3600} \right)}}{{96500}}$
$\Rightarrow {\text{w}} = \dfrac{{109 \times 9.65 \times 3600}}{{4 \times 96500}}$
Solving this, we get:
$\therefore {\text{w}} = 9.81{\text{gm}}$

Therefore the amount of para amino phenol deposited is $9.81$ grams.

Note: The electrochemical equivalent of a substance is the amount of substance deposited or liberated during the electrolysis by the passage of quantity of electricity equal to 1 Faraday which is given as 96500 coulombs per mole. Equivalent weight of an element or compound depends upon the reaction in which that species is involved.