Molarity is the most convenient way to express concentration.
Mathematically, molarity is expressed as [tex] \frac{\text{mass of solute(g)}}{\text{gram molecular weight X Volume of solution (l)}} [/tex]
In present case,
mass of solute (KCl) = 36 g
molecular weight of KCl = 74.55 g/mol
volume of solution = 100 ml = 0.1 l
∴ Molarity = [tex] \frac{36}{74.55X0.1} [/tex]
= 4.829 M
Thus, conc. of saturated KCl at 20 oC is 4.829 M