- 1M NaCl and 1M MgCl2
- 1.5M KCl and 2.5M Urea
- 1.5M AlCl3 and 2M Na2SO4
- 1M NaCl and 2M MgCl2
Solution: 1.5M AlCl3 and 2M Na2SO4
The osmotic pressure and molar concentration in isotonic solutions should be the same or equal.
For AlCl3, I = 4 as AlCl3 dissociates into Al+ and 3Cl– ions
Therefore, the osmotic pressure of 1.5M AlCl3
= iMRT = 4 × 1.5 RT = 6RT
For Na2SO4, i = 3 as Na2SO4 dissociates into 2Na+ and SO42- ions
Therefore, the osmotic pressure of 2M Na2SO4
= iMRT = 3 × 2RT = 6RT
They are isotonic because their osmotic pressures are equivalent.