Solutions Question 15
Question 15 - 01 February - Shift 2
$20 \%$ of acetic acid is dissociated when its $5 g$ is added to $500 mL$ of water. The depression in freezing point of such water is________ $\times 10^{-3}{ }^{\circ} C$. Atomic mass of $C, H$ and $O$ are 12, 1 and 16 a.m.u. respectively.
[Given : Molal depression constant and density of water are $1.86 K kg mol{ }^{-1}$ and $1 g cm^{-3}$ respectively.
Show Answer
Answer: (372)
Solution:
$i=1+(n-1) \alpha$
$(i=1+0.2(2-1)=1.2$
$\Delta T_f=i K_f m$
$\Delta T_f=1.2 \times 1.86 \times \frac{5 \times 1000}{60 \times 500}$
$\Delta t_f=3.72$
$\Delta T_f=372 \times 10^{-2}$
