Dilution Problem

Question

How would you prepare 500 mL of 0.33 M solution of CaCl2 from solid CaCl2? Specify the glassware that would be used.

Answer 1

By definition, 0.33 M means 0.33 moles of CaCl₂ per liter of solution. Since we need only 500 ml (0.5 liters) of solution we calculate as follows:

0.33 mols / L x 0.5 L = 0.165 moles CaCl₂ needed

To find the mass, we calculate as follows using 111 g/mol as the molar mass of CaCl₂:

0.165 mols CaCl₂ x 111 g / mol = 18.3 g CaCl₂

Rounding to 2 significant figures, we need 18 g of CaCl₂ to make the desired solution.

Method of preparation:

Weigh out 18 g of CaCl₂

Transfer to a 500 ml volumetric flask

Dilute with d.H₂O to the 500 ml mark on the volumetric flask.