Answer
0.50 mol is an extensive property, it is a quantity
0.50 M is an intensive property, it is a concentration
Work Step by Step
0.50 mol HCl is 0.50 moles of HCl. This is a quantity that explains how much HCl is present. 0.50 M HCl is 0.50 Molar HCl. It describes the concentration of HCl in moles/Liter.