why does the value of i (van t' hoff factor) change with regards to theoretical vs. experimental?

i'm not quite sure what happens but i know it has to do with ions in the solution. could it be attractive forces between ions?

You are on the right track. Some of it has to do with the percent ionization of a compound. And some has to do with the attractive forces of the ions in solution for each other and for the solvent. And that becomes more of a factor at more concentrated solutions. The limiting value (1 for non-electrolytes, 2 for binary salts such as NaCl and KBr, 3 for Na2SO4, etc) are approached as the solutions become more dilute and at infinite dilution the limiting value is reached.

thanks!

The Van 't Hoff factor (i) represents the number of particles that a solute dissociates into when it is dissolved in a solvent. It is used to calculate colligative properties such as boiling point elevation or freezing point depression.

The theoretical value of i is determined based on the stoichiometry of the solute's formula. It assumes complete dissociation of the solute into its constituent ions, if applicable. For example, a compound like NaCl would have a theoretical i value of 2, as it dissociates into one Na+ ion and one Cl- ion in aqueous solutions.

However, in reality, full dissociation may not always occur due to various factors. One of these factors is the presence of attractive forces between ions in the solution. These attractive forces reduce the degree of dissociation and affect the value of i, making it different from the theoretical value.

Additional factors that can influence the value of i include ion-ion interactions, solute-solvent interactions, and solute-solute interactions. These interactions can lead to partial dissociation and a decrease in the observed i value compared to the theoretical value.

Therefore, the value of i may vary between theoretical and experimental values due to the presence of attractive forces and other factors that affect the degree of ion dissociation in a solution.

The Van 't Hoff factor, denoted as 'i', represents the number of particles that a solute will dissociate into when it dissolves in a solvent. It is used to correctly calculate various colligative properties like boiling point elevation, freezing point depression, and osmotic pressure.

In an ideal, or theoretical, scenario, the Van 't Hoff factor would remain constant for a given solute. For example, if a compound is expected to completely dissociate into three ions when it dissolves, i would be equal to 3.

However, in practice, the experimental value of the Van 't Hoff factor may deviate from the theoretical value. This discrepancy arises because the extent of dissociation of the solute particles depends on various factors, including intermolecular forces present in the solution.

When solute particles dissolve in a solvent, they can interact with each other and form attractive forces, such as ion-ion interactions. These forces can hinder or reduce the degree of dissociation of the solute particles, leading to a lower experimental Van 't Hoff factor compared to the theoretical value.

These attractive forces between ions are known as ion-ion interactions or ion pairing. Ion pairing occurs when oppositely charged ions are attracted to each other and form stable aggregates instead of fully dissociating into free ions in the solution. As a result, the number of particles present in solution is lower than expected, leading to a lower Van 't Hoff factor.

The strength of ion-ion interactions depends on various factors like the size, charge, and solvation properties of the ions, as well as the nature of the solvent. Different solvents may have different abilities to solvate and disrupt these ion-ion interactions, which can influence the observed Van 't Hoff factor in experiments.

In summary, the discrepancy between the theoretical and experimental Van 't Hoff factor arises due to the presence of attractive forces between ions in the solution, which can reduce the extent of dissociation of solute particles and lower the observed value of 'i'.