Question

$50cc$ of oxalic acid is oxidized by $25cc$ of $0.20N$ $KMn{O_4}$. The mass of oxalic acid present in $500cc$ of the solution is:
A.$3.15g$
B.$31.5g$
C.$6.3g$
D.$63g$

Answer 1

At first think about the chemical formula of oxalic acid and the overall reaction of the given question. The chemical formula of oxalic acid is ${H_2}{C_2}{O_4}$. In the given question, the oxalic acid is in its dihydrate form.

Complete step by step answer:
In the question, we have given that
Volume of oxalic acid$= 50cc$
Normality of $KMn{O_4} = 0.20N$
Volume of $KMn{O_4} = 25cc$
The normality of a solution is defined as the measure of concentration equal to the gram equivalent weight per litre of solution.
$N = \dfrac{m}{M} \times \dfrac{1}{V}$
After substituting the values from the question we get,
$0.20 = \dfrac{m}{1} \times \dfrac{{1000}}{{25}}$
$m = 0.005g$ $eq$
$0.005g$ $eq$ of potassium permanganate neutralizes $0.005g$ $eq$of oxalic acid.
The molecular formula of oxalic acid is ${C_2}{H_2}{O_4}.2{H_2}O$.
The equivalent mass of oxalic acid dihydrate is $\dfrac{{126}}{2} = 63g$ $eq$
The mass of oxalic acid dihydrate is $0.05 \times 63 = 0.315g$
$0.315g$ of oxalic acid dihydrate is present in $50cc$ solution. Then $500cc$ solution contains,
$0.315 \times \dfrac{{500}}{{50}} = 3.15g$
The required mass of oxalic acid dihydrate present in $500cc$ is $3.15g$.
So the answer is A.
Additional Information:- Oxalic acid is an organic compound with the chemical formula ${C_2}{H_2}{O_4}$. It is a white crystalline solid that forms a colorless solution in water. It is the simplest dicarboxylic acid. Its acid strength is much greater than that of acetic acid. Oxalic acid is a reducing agent and its conjugate base is known as oxalate which is a chelating agent for metal cations.
Note: Potassium permanganate is standardized against pure oxalic acid. It involves a redox reaction. Potassium permanganate is a strong oxidizing agent and in the presence of sulphuric acid it acts as a powerful oxidizing agent.