In this experiment, the percent composition of copper metal in a copper salt will be
gravimetrically determined by reducing Cu+2 (aq) to solid copper metal. Assuming one copper atom per formula unit (the most common ratio for copper), the formula weight of an unknown copper salt will be calculated.
The copper salt is first weighed, and then dissolved is an acidic solution. The solution will be transparent/clear (not cloudy) and colored blue or green.Small pieces of Mg are put into the blue or blue-green solution. Rxn. 1 takes place on the Mg surface, so the slivery pieces will turn reddish-brown, as the copper metal coats the reacting surface.Once the solution is clear and not colored, more HCl is added, to test that all of the solid Mg is gone.A weighed piece of filter paper is initialed with pencil, folded, and used to filter the precipitated copper metal.