To calculate the osmolarity of a solution, we need to consider the total number of particles contributed by all the solutes present. In the case of a 0.2M KCL solution, we have:

1 mole of KCl → dissociates into 1 mole of K+ ions and 1 mole of Cl- ions

Therefore, the total number of particles contributed by 0.2M KCl is 0.2 moles/L K+ ions + 0.2 moles/L Cl- ions = 0.4 moles/L.

Now, we can directly use the formula for osmolarity:

Osmolarity = Total concentration of particles (in osmoles/L)

In this case, the osmolarity of a 0.2M KCl solution is 0.4 Osm/L.