Question

If $\alpha$ is the degree of dissociation of $N{a}_{2}S{O}_4$, the vant Hoff's factor (i) used for calculating the molecular mass is

• A. $1+\alpha$
• B. $\alpha$
• C. $1+2\alpha$
• D. $1-2\alpha$

Answer 1

The correct option is C $1+2\alpha$

$\underset{1-\alpha }{\underset{}{N{a}_{2}S{O}_4}}\rightleftharpoons \underset{2\alpha }{\underset{}{2N{a}^{+}}}+\underset{\alpha }{\underset{}{S{O}_4^{2-}}}$
Total no. of ions after dissociation = $1+2\alpha$
vant Hoff's factor,$i=\frac{No.ofparticlesafterdissociation}{No.ofparticlesbeforedissociation}=1+2\alpha$