A 4% solution (w/w) of sucrose (M 342 g `mol^(-1)`) in water has a freezing point of 271.15K Calculate the freezing point of 5% glucose (M= 180 g `mol^(-1)`) in water.
(Given: Freezing point of pure water 273.15 K)

Explanation

`DeltaT_(f)=K_(f)m`
`K_(f)=DeltaT_(f) xx (M_(2)xx w_(1))/(w_(2)xx1000)`
`=(2xx342xx96)/(4 xx 1000)=16.4 K`
`DeltaT_(f)=K_(f)m`
`=(K_(f)w_(2)xx1000)/(M_(2)xxw_(1))=(16.4xx5xx1000)/(95xx180)=4.8K`
`Delta T_(f)=T_(f)^(@)-T_(f)`
`4.8=273.15-T_(f)`
`T_(f)=268.35K`