When 0.25 moles of a non-volatile, non-ionizable solute was dissolved in 1 mole of a solvent the vapor pressure of solution was x% of vapor pressure of pure solvent. What is x% ?
- 50%
- 60%
- 70%
- 80%
Answer
(4) 80%
Solution
For a non-volatile, non-ionizable solute (Raoult's law):
ps = xsolvent p
⇒ psp = nsolventnsolvent + nsolute
⇒ psp = 11 + 0.25 = 11.25 = 0.8
∴ Vapour pressure of solution = 80% of that of the pure solvent
Answer: (4)