Relative lowering of vapour pressure of a dilute solution is 0.2 what is the mole fraction of the non- volatile solute?

Relative lowering of vapour pressure is equal to the mole fraction The lowering in vapour pressure is written as, A B 0 A P X ...( ) P i Where, 0 PA A P is the relative lowering in vapour pressure, XB is mole fraction of solute. According to the question 0 P 0.2 A A P Therefore, B X =0.2 (fromequation (i)) Hence the mole fraction of non-volatile solute is 0.2.