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

Question

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?

Answer 1

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.

Answer 2

thanks!