Vapour pressure of pure water at `23^@C` is 19.8 torr . Calculate the vapour of 3m aqueous solution.

Explanation

According to Raoult.s law, relative lowering vapour pressure for a dilute solution is given as
`(p^@-p)/p^@="m x mw of solvent"/1000`
`=(19.8-p)/19.8=(3xx18)/1000=3/55.5`
Vapour pressure of solution,
`p=19.8xx52.55/55.55`=18.73 torr.