3 - When 20.0 mL of a 0.250 M (NH4)2S solution is added to 250.0 mL of a solution of Cu(NO3)2, a Cus precipitate forms. If the weight of the precipitate Cus is measured as 0.349 g, what was the concentration of copper ions in the original Cu(NO3)2 solution? a) 0.0146 M b) 0.0205 M 0.0194 M d) 0.0243 M