Question

A solution containing 62 g ethylene glycol in 250 g water is cooled to -10ºC. If ᴷf for water is 1.86 K kg mol⁻¹, the amount of water(in g) separated as ice is
(A) 48 (B) 32
(C) 64 (D) 16

Answer 1

The amount of water (in g) separated as ice is (C) 64

- GIven :

w = 62 g

Molar mass of ethylene glycol = 62 g

Kf = 1.86 K kg/mol

ΔTf = 10

- But we know that

ΔTf = Kf × m

ΔTf = Kf × ( w × 1000/ M.wt. × W )

10 = 1.86 × ( 62 × 1000/ 62 × W )

W = 186 g

- This amount of water remains unfreezed at -10°C

- So, amount of water converted into ice = Total amount - Amount remaining = 250 - 186 = 64 g