Question

For a dilute solution, Raoult's law states that

• A. lowering of vapour pressure is equal to the mole fraction of the solute
• B. relative lowering of vapour pressure is equal to the mole fraction of the solvent
• C. relative lowering of vapour pressure of the solvent is equal to the mole fraction of the solute
• D. vapour pressure of the solution is equal to the vapour pressure of the solvent

Answer 1

Answer: (C)

relative lowering of vapour pressure of the solvent is equal to the mole fraction of the solute

Answer 2

Raoult's law states that the relative lowering of vapour pressure of the solvent is equal to the mole fraction of the solute, ie, $\frac{p^{o}-p_{s}}{p^{\rho}}=\chi_{s}$ (where, $p^{o}-p_{s}=$ lowering in vapour pressure, $\chi_{s}=$ mole fraction of solute)