CaCl2 ---> Ca2+ + 2 Cl-

i'm trying to figure out the van't hoff factor. i know i=3.

But where did the 2 come from before Cl-.

That's the charge on the Ca ion.

CaCl2 ==> Ca+2 + 2Cl-. And your are correct that i=3. 1 for the Ca ion and 2 more for the Cl^- to make 3.

The 2 before Cl- in the equation CaCl2 → Ca2+ + 2 Cl- represents the stoichiometry of the reaction. In the compound CaCl2, there is one calcium ion (Ca2+) and two chloride ions (2 Cl-). When CaCl2 dissolves in water, it dissociates into one calcium ion and two chloride ions. Therefore, the equation includes the 2 Cl- to reflect the correct ratio of ions produced during the dissociation.

The van't Hoff factor (symbolized as i) is a measure of the number of particles into which a compound dissociates in a solution. In the case of CaCl2, it dissociates into calcium ions (Ca2+) and chloride ions (Cl-).

The equation you provided correctly represents the dissociation of CaCl2 into ions: CaCl2 → Ca2+ + 2 Cl-. The 2 in front of Cl- indicates that each CaCl2 molecule dissociates into two Cl- ions when it dissolves in water.

To determine the van't Hoff factor, you count the number of particles produced by each formula unit when the compound dissociates. In this case, since CaCl2 yields three particles (one Ca2+ ion and two Cl- ions), the van't Hoff factor is i=3.

It's worth noting that not every compound will have the same van't Hoff factor. The van't Hoff factor depends on the extent of dissociation of the compound in solution and can vary based on factors such as temperature and concentration.