Question

What is the freezing point, in °C, of a 0.407 m solution of C5H4 in benzene?​

Answer 1

Answer: 3.416

Step-by-step explanation:

Answer 2

3.396 °C

Step-by-step explanation:

You want to know the freezing point of a 0.407 m solution of C₅H₄ in benzene.

Freezing point depression

The amount of depression of the freezing point is calculated from ...

`\Delta T_f=i\cdot K_f\cdot m`

where i is the van't Hoff factor, Kf is the freezing point depression constant, and m is the molality of the solution. The van't Hoff factor depends on the dissociation of C₅H₄ in benzene solution. There isn't any dissociation, so the van't Hoff factor value is i = 1.

Benzene

The freezing point depression constant for benzene is 5.12 K/molal. This means the amount of freezing point depression of the benzene will be ...

`\Delta T_f=1\cdot(-5.12\text{ K})\cdot0.407\approx-2.084\text{ K}`

The freezing point of pure benzene is 5.48 °C, so the depressed freezing point is ...

5.48 °C -2.084 = 3.396 °C

The freezing point of the solution is about 3.396 °C.