Chemistry Question from JEE Main 2023 · 6 April, Shift 1

Consider the following pairs of solutions which will be isotonic at the same temperature. The number of isotonic pairs is:

1. $1 \, \text{M}$ NaCl and $2 \, \text{M}$ urea
2. $1 \, \text{M}$ CaCl$_2$ and $1.5 \, \text{M}$ KCl
3. $1.5 \, \text{M}$ AlCl$_3$ and $2 \, \text{M}$ Na$_2$SO$_4$
4. $2.5 \, \text{M}$ KCl and $1 \, \text{M}$ Al$_2$(SO$_4$)$_3$