Of the following four aqueous solutions, total number of those solutions whose freezing point is lower than that of 0.10 M C₂H₅OH is __________ (Integer answer)

(i) 0.10 M Ba₃(PO₄)₂

(ii) 0.10 M Na₂SO₄

(iii) 0.10 M KCl

(iv) 0.10 M Li₃PO₄

The OH^$$-$$ concentration in a mixture of 5.0 mL of 0.0504 M NH₄Cl and 2 mL of 0.0210 M NH₃ solution is x $$\times$$ 10^$$-$$6 M. The value of x is ___________. (Nearest integer)

[Given K_w = 1 $$\times$$ 10^$$-$$14 and K_b = 1.8 $$\times$$ 10^$$-$$5]

The number of 4f electrons in the ground statement electronic configuration of Gd²⁺ is ___________. [Atomic number of Gd = 64]

The ratio of number of water molecules in Mohr's salt and potash alum is ____________ $$\times$$ 10^$$-$$1. (Integer answer)