Question

Mole fraction of A in H2O is 0.2.The molality of A in H2O is:

Answer 1

The answer for this question is 13.8

Answer 2

Answer : The molality of A in water is 13.889 mole/Kg.

Solution : Given,

Solute = A and Solvent = Water

Mole fraction of A= 0.2

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

$Molality=\frac{0.2mole\times 1000}{(1-0.2)mole\times (18Kg/mole)}=13.889mole/Kg$

Therefore, the molality of solution is 13.889 mole/Kg.