Question

an aqueous solution containing0.25 gm of solute os dissolved in 20 gm of water the solution freezes at -0.4°C .Calculate molar mass of unknow solute​

Answer 1

Answer:

The molar mass of the unknown solute is 58.125g/mol

Explanation:

Given:

W₂= 0.25 g, W₁=20 g, Tf= -0.4° C, additionally,

Kf (for water) = 1.86 K kg/ mol, and T°f=273K (by common knowledge)

Solution:

Tf = -0.4 + 273 = 272.6 K

ΔTf = 273K - 272.6= 0.4K

M₂  =  (Kf × W₂ × 1000) / (ΔTf × W₁)

      = (1.86 x 0.25 x 1000) / (0.4x20)

      = 58.125 g/mol