Question

Which of the following relations is not correctly matched with the formula?

• A. In case of association $\alpha = \frac{i - 1}{\frac{1}{n} - 1}$
• B. In case of dissociation $\alpha = \frac{i - 1}{n + 1}$
• C. Relative lowering of vapour pressure $= \frac{Pº_{A} - P_{A}}{Pº_{A}} = i\frac{n_{B}}{n_{A} + n_{B}}$
• D. Elevation in boiling point$\Delta T_{b} = K_{b} \times \frac{W_{B} \times 1000}{M_{B} \times W_{A}}$

Answer 1

Answer: (B)

In case of dissociation $\alpha = \frac{i - 1}{n + 1}$

Answer 2

In case of dissociation: $A_{n}\overset{\quad\quad}{\rightarrow}nA$

Initial number of moles

1 0

After dissociation

$1 - \alpha$ $n\alpha$

No. of particles$= 1 - \alpha + n\alpha$

$i = \frac{1 - \alpha + n\alpha}{1}ori = 1 - \alpha + n\alpha$

$i - 1 = n\alpha - \alpha = (n - 1)\alpha\therefore\alpha = \frac{i - 1}{n - 1}$