At 300 K , when a solute is aded to a solvent ,its vapour pressure over mercury reduces from 50 mm to 45 mm . The value of mole fraction of solute wil be _____.

Options

A. `0.005`
B. `0.010`
C. `0.100`
D. `0.900`

Answer

C

Explanation

Vapour pressure of solvent `P_(0)=50mm`
Vapour pressure of solution P = 45mm
Mole fraction of solute `=(P_(0)-P)/(P_(0))=(50-45)/(50)`
`=(5)/(50)=0.1`.