The objective of this experiment is to determine the percent copper and formula weight of a copper compound. The formula weight of a compound can be calculated from the percent-by-weight of an element in the compound, Cu in this case, if the number of atoms of that element in the compound is known.
You will determine the percent copper in a compound by dissolving the copper salt in an aqueous solution and reducing the copper(II) ions to metallic copper with magnesium, a very reactive metal:
Cu2+ (aq) + Mg(s) —› Cu(s) + Mg2+ (aq)
The metallic copper formed will be collected, washed, dried and weighed. You will then use the percent copper in the compound to calculate the formula weight of your compound.