Question

substance A tetramerises in water to a extent of 80% . A solution of 2.5g of A in 100g of water lowers the freezing point by 0.3degree C . The molar mass of A is

1) 122

2) 31

3) 244

4) 62

Answer 1

Option 4 is correct. Molecular mass of A = 62 u.

Lowering of freezing point due to colligative properties is:

T = i.k.m

Vant Hoff factor (i) = 0.4
Given that T = 0.3 K, m = 25 / M (M = Molar mass of A), k = 1.86

Substituting these values:

0.3 = 0.4 x 1.86 x 25 / M
M = 62