Set up your problem using conversion factors like this: (5g Ca(ClO)2/100mL) x (1 mol/molar mass Ca(ClO)2) x (1000mL/1L) = molarity of your solution.

Once you cancel all of the units, you will be left with mol/1L, which of course is the molarity. The 100mL in the denominator of the first term and the 1000mL in the numerator of the last term give you the "10x" Rosy was talking about. Just so you understand why, molarity is always based on a liter. To make a 1M solution of something, you add 1 mole of solute to a volumetric flask, then fill to the 1L mark with water.