The amount (in grams) of sucrose ( m o l w t . = 342 g ) that should be dissolved in 100 g water in order to produce a solution with a 105 . 0 o C difference between the freezing point and boiling point is (Given that K f = 1.86 K kg mol − 1 and K b = 0.51 K kg mol − 1 for water)

Step-by-step solution

Boiling point T b = 100 + ∆ T b = 100 + k b m Freezing point T f = 0 - ∆ T f = - k f m T b - T f = 100 + k b m - ( - k f m ) 105 = 100 + 0 . 51 m + 1.86 m 2 .37 m = 5 or m = 5 2 .37 = 2 .11 ∴ Weight of sucrose to be dissolved in 100 g water = 2.11 × 342 1000 × 100 = 72.2 g