Question

The mass of oxalic acid crystals $\left(H_2{C}_2{O}_4{2H}_{2}O\right)$ required to prepare $50mL$ of a $0.2N$ solution is: [Assume both $H^{+}$ are replaced in the reaction]

• A. $4.5g$
• B. $6.3g$
• C. $0.63g$
• D. $0.45g$

Answer 1

The correct option is C $0.63g$

Molar mass of oxalic acid crystals=$126gmo{l}^{-1}$

Normality= $n\times Molarity$ (n is the n-factor)

$C_2{O}_4^{2-}⟶2C{O}_2$

Change in oxidation state for $C$ is $1$

therefore, change in oxidation state for $C_2{O}_4^{2-}$ is $2$

$\therefore$ Normality=$2\times Molarity$

$\therefore 0.2=2\times \frac{m/126}{0.050}$

$\therefore m=0.63g$