Question

Calculate freezing point depression expected for 0.0711 m aqueous solution of Na₂SO₄. If this solution actually freezes at – 0.320°C, what will be the value of van't Hoff factor? (kg for water = 108b°C mol^–1)

विकल्प

• 142 K

• 242 K

• 420 K

• 224 K

Answer 1

242 K

Explanation:

Calculated of normal value of ΔTf = Kt × m

kf = l .86°C mol^–1 = 1.86 k kg mol^–1

m = 0.071 mol kg^–1

ΔTf = (1.86 k kg mol^–1) × (0.0711 mol kg^–1) = 0.132 k

Step – II calculation of van't Hoff factor

Van't Holf factor ('s) = `"Actual value and TF"/("Normal value of"  ΔTF)`

Acutal value of ΔTf = 0 – (– 0.320) = 0.320C = 0.320 K.

J = `((0.320  k)/(0.132  k))` = 242