Question

$1.520g$ of the hydroxide of a metal on ignition gave $0.995g$ of oxide. The equivalent mass of metal is:

• A. $1.52$
• B. $0.995$
• C. $190$
• D. $2$

Answer 1

The correct option is D $2$

$FirstcalculatetheNormalityof$

$N{a}_{2}C{O}_3.x{H}_{2}O$

$Normality=\frac{no.ofmoles}{Vol.}$

$=\frac{mass}{molarmass}\times \frac{1000}{Vol.\left(ml\right)}$

$=\frac{0.7}{53+9x}\times \frac{1000}{100}=\frac{0.7}{53+9x}\times 10N$

$[\therefore waterofcrystallisation=18\times x]$

$eq.becomes=\frac{18x}{2}=9x$

$By,Normalityformula,N_1{V}_1=N_2{V}_2$

$\frac{7\times 20}{53+9x}=19.8\times 0.1$

$\frac{140}{1.98}=53+9x\Rightarrow x=\frac{17.7}{9}=1.96\approx 2$

$So,thecorrectanswerwillbe{}^{\prime }{2}^{\prime }.$