Question

Studies on the elevation in boiling point of $Ca(N{O}_3{)}_2$ gives its molar mass to be $131.2\text{g/mol}$. The degree of dissociation of $Ca(N{O}_3{)}_2$ is:

• A. $100\%$
• B. $75\%$
• C. $50\%$
• D. $12.5\%$

Answer 1

The correct option is D $12.5\%$

$Ca(N{O}_3{)}_2\to C{a}^{2+}+2N{O}_3^{-}Initial100At.eq1-\alpha \alpha 2\alpha$
As we know, $i=1+2\alpha$
Calculated molecular weight of $Ca(N{O}_3{)}_2=164g/mol$
Observed Molecular weight of $Ca(N{O}_3{)}_2=131.2g/mol$
$i=\frac{164}{131.2}=1+2\alpha$
$\therefore \alpha =0.125=12.5\%$