In a 0.2 molal aqueous solution of a weak acid HX the degree... | Chemistry | SolveeIt | Solveeit

Today, August 18

Question

In a 0.2 molal aqueous solution of a weak acid HX the degree of ionization is 0.3. Taking $K_f$ for water as 1.85, the freezing point of the solution will be nearest to

A

-0.480 $^\circ$ C

B

-0.360 $^\circ$ C

C

-0.260 $^\circ$ C

D

#ERROR!

Answer

-0.480 $^\circ$ C

Explanation

Solution

${ HX <=> H^+ + X^-}$ $i = \frac{1 - 0.3 + 0.3 + 0.3 }{1} = 1.3$ $\Delta T_f = i \, K_f \, m$ = $1.3 \times 1.85 \times 0.2$ = 0.48 $\therefore$ $T_f$ = (0 - 0.48) $^{\circ}$ C = 0-48 $^{\circ}$ C.