colligative properties#!#vant hoff factor#!#most important questions

Vant Hoff factor (i)-

What is Van't Hoff factor ?

, van't -Hoff factor (i) for this reaction is:

In the determination of molar mass of A^(+)B(-) using colligative property, what will be the Van't Hoff factor if the solute is 40% dissociated ?