Question

50 cc of oxalic is oxidized by 25 cc of 0.20 N $KMn{O}_4.$ The mass of oxalic acid present in 500 cc of the solution is.

• A. 3.15g
• B. 31.5g
• C. 6.3g
• D. 63g

Answer 1

The correct option is A 3.15g

25cc of 0.20 N $KMn{O}_4$ corresponds to $\frac{\text{25 mL}}{1000mL/L}\times \text{0.20 g eq /L}=\text{0.005 g eq}$
0.005 g eq of $KMn{O}_4$ will neutralise 0.005 g eq of oxalic acid.
The equivalent mass of oxalic acid dihydrate is $\frac{\text{126 g/mol}}{2}\text{63 g/eq}$
The mass of oxalic acid dihydrate is $\text{0.005 g eq}\text{63 g/eq}=\text{0.315 g}$
This is present in 50 cc of solution. 500 cc of solution contains
$\text{0.315 g}\times \frac{\text{500 cc}}{\text{50 cc}}=\text{3.15 g}$