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^@) = (n_("solute"))/(n_("solven")) , (19.8 - p)/(19.8) = 3/(55.5)`
Vapour pressure of solution, `p = 19.8 xx (52.55)/(55.55) = 18.73` torr.