The "I factor" refers to the Van't Hoff factor, which is a measure of the extent to which a solute dissociates into ions in a solution. It is denoted by the symbol "i" and represents the number of particles into which one molecule of the solute dissociates.
When a salt dissolves in water, it may break apart into its constituent ions. For example, table salt (NaCl) dissociates into sodium ions (Na+) and chloride ions (Cl-) in an aqueous solution. The Van't Hoff factor for NaCl is 2 because one molecule of NaCl dissociates into two ions (Na+ and Cl-).
Now, let's consider the situation where the concentration of the dissolved salt is increased. As more solute particles are added to the solution, the interparticle distance decreases, leading to increased electrostatic interactions between the ions. These interactions can affect the degree of dissociation of the salt.
At higher concentrations, the electrostatic forces between the ions become more significant. This increased ion-ion interaction can cause some ions to associate or recombine with each other, forming ion pairs or complexes. As a result, the actual number of particles in solution may be lower than expected based on the stoichiometry of the dissolved salt.
In other words, as the concentration increases, the tendency for ion pairing or complex formation becomes more pronounced, leading to a decrease in the effective number of particles formed by each solute molecule. Consequently, the Van't Hoff factor (i) decreases for the dissolved salt as its concentration is increased.
It's important to note that the decrease in the Van't Hoff factor is not observed for all dissolved salts. Some salts may exhibit a constant Van't Hoff factor, while others may even show an increase in the Van't Hoff factor with increasing concentration. The behavior depends on the specific properties of the solute and the solvent system involved.