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# 2 molal solution of a weak acid HA has a freezing

Question:

2 molal solution of a weak acid HA has a freezing point of $3.885^{\circ} \mathrm{C}$. The degree of dissociation of this acid is_______ $\times 10^{-3}$. (Round off to the Nearest Integer).

[Given : Molal depression constant of water $=$ $1.85 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$ Freezing point of pure water $\left.=0^{\circ} \mathrm{C}\right]$

Solution:

$\Delta \mathrm{T}_{\mathrm{f}}=(1+\alpha) \mathrm{K}_{\mathrm{f}} \mathrm{m}$

$\alpha=0.05=50 \times 10^{-3}$