Question

$25gm$ mixture of ${Na}_2{CO}_3$ and ${Na}_2{SO}_4$ are dissolved in $250ml$ of solution. $25ml$ of above solution required $20ml$ of $0.1N$ $H_2{SO}_4$ using phenolphthalein indicator. The mass of ${Na}_2{CO}_3$ in the mixture is:

• A. $1.5gm$
• B. $2.12gm$
• C. $2.05gm$
• D. $1.6gm$

Answer 1

The correct option is A $1.5gm$

When a mixture of $N{a}_{2}C{O}_3$ and $N{a}_{2}S{O}_4$ are dissolved in $H_{2}S{O}_4,N{a}_{2}S{O}_4$ being similar to $H_{2}S{O}_4$ anions, does not involve in $H_{2}S{O}_4$.

So, Gram equivalent of $N{a}_{2}C{O}_3$ = Gram equivalent of $H_{2}S{O}_4$

moles $\times$ n-factor = Normality $\times$ Volume

.

$\frac{w}{106}\times 2=0.1\times \frac{20}{1000}$

$w=\frac{2\times 106}{1000\times 2}$

$w=1.5gm$

Option A is correct