Which one of the following pairs of solution will be isotonic at the same temperature ?

Q: Which one of the following pairs of solution will be isotonic at the same temperature ?

(A) 1 M NaCl & 2 M – Urea

(B) 1 M CaCl2 & 1.5 M – KCl

(C) 1.5 M AlCl3 & 2 M Na2SO4

(D) 2.5 M KCl and 1 M – Al2(SO4)3

Solution: For
(A) 1M NaCl solution (i × Cm) = 2 × 1M (Cm = Molarity)

2M Urea solution (i × Cm) = 2M

1M CaCl2 solution (i × Cm) = 3 × 1M = 3M

1.5 M KCl solution (i × Cm) = 2 × 1.5M = 3M

Similarly for 1.5 M AlCl3 and 2M Na2SO4

The value of i × Cm be 6

and 2.5 M KCl and 1M Al2(SO4)3 has 5 M each.

So, the each pair of solution

A,B,C and D have same concentration so, all pairs of solution be isotonic,

Answer : A,B,C and D