(a) Define the following terms :
(i) Mole fraction
(ii) Ideal solution
(b) `15.0`g of an unknown molecular material is dissolved in 450g of water . The resulting solution freezes at `-0.34^(@)C` . What is the molar mass of the material ?
`(K_(f)` for water = `1.86` K kg `mol^(-1))`

Explanation

`M_(B) = (K_(f) xx 1000 xx w_(B))/(w_(A) xx Delta T_(f))`
`Delta T_(f) = 273 -271.4 = 1.6 K`
`M_(B) = (1.86 xx 1000 xx 31)/(500 xx 1.6) = 72.1 g mol^(-1)`