The van’t Hoff factor, named after the Dutch chemist Jacobus Henricus van’t Hoff, is a measure of the degree of dissociation or the number of particles that a solute molecule breaks into when it dissolves in a solvent. It is denoted by the symbol “i”.

The van’t Hoff factor is particularly relevant for solutes that dissociate into ions when they dissolve in a solvent, such as ionic compounds or some molecular compounds that ionize in solution. It represents the ratio of the moles of particles formed in solution to the moles of solute molecules initially added.

For example, when a salt like sodium chloride (NaCl) dissolves in water, it dissociates into sodium ions (Na+) and chloride ions (Cl-). In this case, the van’t Hoff factor would be 2 because each NaCl molecule dissociates into two ions. Similarly, a compound like calcium chloride (CaCl2) would have a van’t Hoff factor of 3 because it dissociates into three ions (one calcium ion and two chloride ions).

However, it’s important to note that the van’t Hoff factor is not always equal to the actual number of ions formed in solution. It is an empirical value that depends on the nature of the solute and the solvent. Factors such as solute-solvent interactions, association or complex formation, and temperature can affect the degree of dissociation and influence the van’t Hoff factor.

The van’t Hoff factor is significant in various aspects of chemistry, including colligative properties of solutions, osmotic pressure, boiling point elevation, and freezing point depression. It allows for the calculation of the actual concentration of solute particles in solution and helps in predicting and understanding the behavior of solutions with ionic or ionizable solutes.