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Question:

Molal depression constant for a solvent is 4.0 kg mol⁻¹. The depression in the freezing point of the solvent for 0.03 mol kg⁻¹ solution of K₂SO₄ is: (Assume complete dissociation of the electrolyte)

0.18 K

0.12 K

0.36 K

0.24 K

Solution:

Correct option is B. 0.36 K
Given that,
Kf = 4 K.kg/mol
m = 0.03 mol/kg
i = 3
Now,
ΔTf = i × Kf × m
ΔTf = 3 × 4 × 0.03 = 0.36 K