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)

Answer

268.35K

Explanation

For surcose solution.
`w_(B) = 4 g ,w_(A) = 100 - 4 = 96 g`
`Delta T_(f) = 273.15-271.15 = 2 K`
`k_(f) = (Delta T_(f) xx w_(A) xx M_(B))/(w_(B) xx 1000)`
` = ( 2 xx 96xx342)/(4 xx 1000) = 16.416 K m^(-1)`
` = (16.415 xx 5 xx 1000)/(95 xx 180) = 4.8 K`
Freezing point of glucose solution `= 273.15-4.8 K`