Question

The vapour pressure of pure liquid solvent a is 0.80 atm. When a non-volatile substance b is added to the solvent, its vapour pressure drops to 0.60 atm. Mol fraction of the component b in the solution is

Answer 1

In solution containing several non-volatile solutes, the lowering of the vapour pressure depends on the sum of the mole fraction of different solutes.

This translates to the equation p0−pp0p0−pp0=x2=x2, the expression on the left hand side is called the relative lowering of vapour pressure and is equal to the mole fraction of the solute.

0.80−0.400.800.80−0.400.80=x2=0.5=x2=0.5