Considering a 1.0M of each solution, which has the greatest osmolarity?

1. FeCl3
2. K2O
3. HCl
4. HC2H3O2

1 answer

pi = i*M*RT
All other things being equal, the one with the largest i will have the largest pi. So you know how to do i? It is the van't Hoff factor and is the number of particles per mole of the compound.