Addition of a non-volatile solute causes lowering in vapour pressure of a solvent from 0.8 atm to 0.2 atm. What is the mole fraction of solvent?

Raoult’s Law is given by the following formula- 2 2 2 2 0.8 0.2 0.8 0.6 0.8 0.75 o s o P P x P x x x >> >> >> This is the mole fraction of solute. Now, the mole fraction of solvent = 1 – 0.75 = 0.25 Thus, the correct option is (a) 0.25