We have three aqueous solutions of NaCl labelled as 'A', 'B' and 'C' with concentration 0.1 M, 0.01 M and 0.001 M, respectively. The value of van 't Hoff factor (i) for these solutions will be in the order :
- iA < iC < iB
- iA < iB < iC
- iA > iB > iC
- iA = iB = iC
Answer
(2) iA < iB < iC
Solution
NaCl → Na+ + Cl- ⇒ ideal i = 2
∵ on dilution interionic attraction decreases ⇒ i rises towards 2
Observed i: 0.1 M (A) = 1.87; 0.01 M (B) = 1.94; 0.001 M (C) = 1.97
⇒ iA < iB < iC
Answer: (2)