For which among the following equimolar aqueous solutions Van’t Hoff factor has the lowest value?
(A) Aluminium Chloride (B) Potassium Sulphate
(C) Ammonium Chloride (D) Urea

The correct option is (d) Urea. In this solution, the urea molecules neither associate nor dissociate so, effectively Van't Hoff factor remains 1. But, in other cases the number of particles increase when dissolved in water. For, AlCl₃, K₂SO₄ and NH₄Cl number of particles formed per molecule is 4,3 and 2 respectively. Thus, Van't Hoff factor is greater than 1.