JEE MAIN - Chemistry (2022 - 26th June Morning Shift - No. 13)
A 0.5 percent solution of potassium chloride was found to freeze at $$-$$0.24$$^\circ$$C. The percentage dissociation of potassium chloride is ______________. (Nearest integer)
(Molal depression constant for water is 1.80 K kg mol$$-$$1 and molar mass of KCl is 74.6 g mol$$-$$1)
Answer
98
Explanation
$\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{iK}_{\mathrm{b}} \mathrm{m}$
$$ \begin{aligned} &\mathrm{i}=\frac{0.24 \times 99.5 \times 74.6}{1.80 \times 0.5 \times 1000} \\\\ &=1.98 \\\\ &\alpha=\frac{\mathrm{i}-1}{\mathrm{n}-1}=\frac{0.98}{1}=0.98 = 98 \,\% \end{aligned} $$
$$ \begin{aligned} &\mathrm{i}=\frac{0.24 \times 99.5 \times 74.6}{1.80 \times 0.5 \times 1000} \\\\ &=1.98 \\\\ &\alpha=\frac{\mathrm{i}-1}{\mathrm{n}-1}=\frac{0.98}{1}=0.98 = 98 \,\% \end{aligned} $$
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