The van’t Hoff factor, i, accounts for:

The correct answer is Option (1) → The extent of dissociation or association of the solute

Colligative properties depend on the number of solute particles. An electrolyte that dissociates into ions gives more particles, and a solute that associates (for example ethanoic acid forming dimers in benzene) gives fewer. The van’t Hoff factor i corrects for this change in the number of particles: i > 1 for dissociation and i < 1 for association.

Why the other options are incorrect

Option (2) The extent of dissolution of the solute — Incorrect. i does not measure how much solute dissolves; it compares the number of particles after dissociation or association with the number before.

Option (3) The degree of decomposition of the solute — Incorrect. The solute is not broken down into new substances; it only splits into ions or joins into larger units in the solution.

Option (4) The volatility of the solute — Incorrect. These colligative properties are for non-volatile solutes, and i has nothing to do with how easily the solute evaporates.

NCERT (2026-27 edition):
1.7 Abnormal Molar Masses – “In 1880 van’t Hoff introduced a factor i, known as the van’t Hoff factor, to account for the extent of dissociation or association.”