Q20 / 180 · KCET 2012 · Chemistry
The volume of $0.1 \mathrm{M}$ oxalic acid that can be completely oxidized by $20 \mathrm{~mL}$ of $0.025 \mathrm{M}$ $\mathrm{KMnO}_{4}$ solution is
- A$25 \mathrm{~mL}$
- Correct answerB$12.5 \mathrm{~mL}$
- C$37.5 \mathrm{~mL}$
- D$125 \mathrm{~mL}$
Solution
$\mathrm{N}=\frac{\text { molecular weight }}{\text { equivalent weight }} \times \mathrm{M}$
$$
\begin{aligned}
\mathrm{N}_{\mathrm{KMnO}_{4}} &=\frac{158}{31.6} \times 0.025 \\
&=0.125 \\
\mathrm{~N}_{\mathrm{O} . \mathrm{A}} &=\frac{126}{63} \times 0.1=0.2 \\
\because \quad \mathrm{N}_{\mathrm{V}} \mathrm{V}_{1} &=\mathrm{N}_{2} \mathrm{~V}_{2} \\
0.2 \times \mathrm{V} &=0.125 \times 20 \\
\therefore \quad & 0.125 \times 20 \\
\mathrm{~V} &=0.2 \\
&=12.5 \mathrm{~mL}
\end{aligned}
$$
Hence, the correct answer is option: 'B'.