Question

If $\alpha$ is the degree of dissociation of $N{a}_{2}S{O}_4$ the van't Hoff''s factor $\left(i\right)$ used for calculating the molecular mass is

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

Answer 1

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

$N{a}_{2}S{O}_4\rightleftharpoons 2N{a}^{+}+S{O}_4^{2-}$
$$\begin{array}{ccc}1& 0& 0\\ 1-\alpha & 2\alpha & \alpha \end{array}$$
Van't Hoff factor (i) $=\frac{1-\alpha +2\alpha +\alpha }{1}=1+2\alpha$