No. of moles of calcium chloride = molarity × volume of solution in L
No. of moles of calcium chloride = 2.5 ×0.5 = 1.25 mole
No. of moles of calcium chloride = mass of calcium chloride / molar mass of calcium chloride
1.25 mole = mass of calcium chloride / 110.98 g/mol
mass of calcium chloride = 1.25 ×110.98 = 139 g