Question

If $\alpha$ is the degree of dissociation of $Na_{2}SO_{4}$ the van’t Hoff’s factor (i) is used for calculating the molecular mass is

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

Answer 1

Answer: (C)

$1 + 2\alpha$

Answer 2

$Na_{2}SO_{4}$ $2Na^{+} + SO_{4}^{2 -}$

1 0 0

$1 - \alpha$ $2\alpha$ $\alpha$

Van’t Hoff factor $(i) = \frac{1 - \alpha + 2\alpha + \alpha}{1} = 1 + 2\alpha$