Van't Hoff factor for $\text{Na}_2\text{SO}_4\cdot10\text{H}_2\text{O}$ solution, assuming complete ionisation is:

3

The correct answer is Option (2) → 3 ##

The molecule $\text{Na}_2\text{SO}_4\cdot10\text{H}_2\text{O}$ dissociates as follows:

• $2\text{ Na}^+$
• $1\text{ SO}_4^{2-}$
• $10\text{ H}_2\text{O}$

Since water is a non-electrolyte, it does not ionise and does not contribute to the van't Hoff factor value.