Boiling point of water 750 mm Hg is `99.63^(@)C`. How much sucrose is to be added to 500 g of water such that it boils at `100^(@)C`.
`[K_(b)` for water is `0.52" K kg mol"^(-1)]`
i) Since boiling point is changing, apply the formula for elevation in boiling point,
`Delta"T"_(b)=K_(b)m`
ii) `m=(W_(B))/(M_(B).W_(A))`
So, `DeltaT_(b)=(K_(b).W_(B))/(M_(B)xxW_(A))`
Or `W_(B)=(DeltaT_(b)xxM_(B)xxW_(A))/(K_(b))`
iii) Find `DeltaT_(b)" as "DeltaT_(b)=T_(b)=T_(b)-T_(b)^(0)`
`T_(b)`= Boiling point of solution
`T_(b)^(0)` = Boiling point of pure solvent

Explanation

`1.86 ` g