Question

$0.7gm$ of ${Na}_2{CO}_3.x{H}_{2}O$ is dissolved in $100ml$, $20ml$ of which required $19.8ml$ of $0.1N$ $HCl$. The value of $x$ is :

• A. 4
• B. 3
• C. 2
• D. 1

Answer 1

Answer: (C)

2

meq of ${Na}_2{CO}_3.x{H}_{2}O$ in $20ml$ = meq of $HCl$ (used)

$\frac{0.7}{\left(\frac{106+18x}{2}\right)}\times 1000\times \frac{20}{100}=19.8\times 0.1$
[n-factor for $N{a}_{2}C{O}_3=2$]

Calculating the value of $x$ we have:

$x\approx 2$