Question

calculate molality of solution of ethyl alcohol in water if mole fraction of ethyl alcohol is 0.04

Answer 1

Answer : The molality of solution is 2.315 mole/Kg.

Solution : Given,

Solute = Ethyl alcohol

Solvent = Water

Mole fraction of ethyl alcohol = 0.04

Molar mass of water = 18 g/mole

The relation between the mole fraction and the molality is,

$Molality=\frac{x_B\times 1000}{(1-x_B)\times M_A}$

where,

$x_B$ = Mole fraction of solute

$M_A$ = Molar mass of solvent

Now put all the given values in above formula, we get the molality.

$Molality=\frac{0.04mole\times 1000}{(1-0.04)mole\times (18Kg/mole)}=2.315Kg/mole$

Therefore, the molality of solution is 2.315 mole/Kg.