Here's how to calculate the molarity of a KCl solution:

1. Convert grams of KCl to moles:

* Molar mass of KCl: 39.10 g/mol (K) + 35.45 g/mol (Cl) = 74.55 g/mol

* Moles of KCl: (5.0 g KCl) / (74.55 g/mol) = 0.067 mol KCl

2. Convert mL of solution to liters:

* Liters of solution: (100 mL) * (1 L / 1000 mL) = 0.1 L

3. Calculate Molarity:

* Molarity (M) = moles of solute / liters of solution

* Molarity = (0.067 mol KCl) / (0.1 L) = 0.67 M

Therefore, the molarity of the solution is 0.67 M.