Now remember, method 2, we can use osmolarity equals number of ions times the molarity of the compound. Here in this example, it says, what is the concentration of hydroxide ions in a 0.350 molar solution of Gallium Hydroxide, which has a formula of Ga(OH)₃. Alright. So we need to find the osmolarity of hydroxide ions.

The molarity of OH^- ions equals the number of hydroxide ions. If we take a look here at the formula, we see that there's a 3 here, meaning that there are 3 hydroxides within this parenthesis. So that would be 3 times the molarity of the original compound. Gallium hydroxide as a compound has a molarity of 0.350 molar. So now just do 3 times that value and when we do that we get 1.05 molar as the osmolarity of hydroxide ions. So it's as simple as that. If you know the molarity of the compound overall, use that to help you find the odd molarity of any one of its ions.