Q. A salt MA₂ ionises as
$\text{MA}_{2} \rightleftharpoons \text{M}^{2 +} + 2 \text{A}^{-}$
It was found that a given solution of the salt had the same freezing point as solution of glucose of twice the molality. The apparent degree of ionization of the salt is

NTA AbhyasNTA Abhyas 2022 Report Error

0.25

0.33

0.50

0.67

Solution:

$\text{MA}_{2} & \rightleftharpoons & \text{M}^{2 +} & + & 2\text{A}^{-} \\ 1-\text{α} & & \text{α} & & 2\text{α}$
$\text{i} = \frac{\text{Actual no. of particles in solution}}{\text{Number of particles taken}}$
$\text{i} = 1 + 2 \text{α}$
$\Delta \text{T}_{\text{} \text{} \text{f} }$ of $\text{MA}_{2} = \Delta \text{T}_{\text{} \text{} \text{f} }$ of glucose
$\text{i} \cdot \text{K}_{\text{f}} \cdot \text{m} = \text{K}_{\text{f}} \cdot 2 \text{m} \times \text{i}$
$1 + 2 \text{α} = 2 \Rightarrow 2 \text{α} = 1 \Rightarrow \text{α} = \text{0.5}$

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Q. A salt MA2 ionises as $\text{MA}_{2} \rightleftharpoons \text{M}^{2 +} + 2 \text{A}^{-}$ It was found that a given solution of the salt had the same freezing point as solution of glucose of twice the molality. The apparent degree of ionization of the salt is