Calculate the freezing point of a solution containing 1.25g of benzene in 100g of chloroform

The freezing point of chloroform (CHCl₃) in presence of benzene = - 64.252 °C.

Explanation:

ΔTf = Kf.m,

Where, ΔTf is the elevation of freezing point,

Kf is the freezing point depression constant (Kf of chloroform = 4.7 °C/m),

m is the molality of the solution.

m = (mass / molar mass) solute (benzene) x (1000 / mass of solvent (CHCl₃))

m = (1.25  g / 78.11 g/mol) x (1000 / 100.0 g) = 0.160 m.

ΔTf = Kf.m = (4.70 °C/m) (0.160 m) = 0.752 °C.

∴ The freezing point in presence of benzene = The freezing point of pure CHCl₃ - ΔTf = - 63.50 °C – 0.752 °C = - 64.252 °C.

your answer would be a. 12.5 kg

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