Question

The vapor pressure of pure water at 30°C is 40 torr. If NaCl is dissolved into a sample of water until the total vapor pressure of the mixture at 30°C is 32 torr, what is the mole fraction of NaCl?

Answer 1

Mole fraction is 0.2

Step-by-step explanation:

You have to apply the colligative property about vapour pressure which formula is:

ΔP = P° .Xm

Where ΔP = P° - P

Pressure of vapour from pure solvent (P°) - Pressure of vapour from solution

40 Torr - 32 Torr = 40 Torr . Xm

8 Torr / 40 Torr= 0.2. > Xm