The vapour pressure of water is `12.3 kPa` at `300 K`. Calculate vapour pressure of `1` molal solution of a solute in it.

Explanation

1 molal solution means 1 mol of the solute in 1 kg of the solvent (water).
`therefore" Mol fraction fraction of solute "=(1)/(1+55.5)=0.0177`
`"Now, "(p^(@)-p_(s))/(p^(@))=x_(2), i.e.,(12.3-p_(s))/(12.3)=0.0177" or "p_(s)="12.08 kPa."`