Identify the Solute with the Highest Van’t Hoff Factor: FeCl₃

Answer

E. FeCl₃ has the highest van’t Hoff factor among these choices.

For an ideal dilute solution, the van’t Hoff factor, $i$, is the number of dissolved particles produced per formula unit. Assuming complete dissociation:

• MgCl₂ → Mg²⁺ + 2 Cl⁻, so $i = 3$
• MgSO₄ → Mg²⁺ + SO₄²⁻, so $i = 2$
• NaCl → Na⁺ + Cl⁻, so $i = 2$
• A nonelectrolyte remains as intact molecules, so $i = 1$
• FeCl₃ → Fe³⁺ + 3 Cl⁻, so $i = 4$

Because FeCl₃ produces the largest number of particles per formula unit, it has the largest ideal value of $i$. OpenStax’s measured data for 0.050 m solutions preserve the same ranking at the top: FeCl₃ has a measured factor of 3.4, compared with 2.7 for MgCl₂, 1.9 for NaCl, 1.3 for MgSO₄, and 1.0 for a nonelectrolyte.

Do not compare the magnitudes of ionic charges. The factor counts effective dissolved particles, not total charge.