Calculations for the percent yield of copper Mass of copper(II) chloride dihydrate ( g ) 0.7780 Appearance of solution Mass of aluminum added (g) Mass of watch glass (g) 0.1249 Mass of watch glass and copper (g) 58.3180 Appearance of copper Mass of copper (g) \begin{tabular}{|ll|} \hlineBIU & X2X2 \\ \hline \end{tabular} Theoretical mass of copper metal in initial sample (g) Percent yield of copper from the reaction (\%)