what minimum mass of copper ii nitrate must be added to 70 ml of a .0594 M phosphate solution in order to completely precipitate all the phosphate as solid copper ii phosphate. 2PO4^-3+3Cu(NO3)2-->Cu3(PO4)2+6NO3^-1

Question

I can not come up with the correct answer of 1.17g

Answer 1

mols PO4^3- = M x L = 0.0594 x 0.070 = 0.004158
Convert to mols Cu(NO3)2 = 0.004158 x (3 mols Cu/2 mols PO4^2-) = 0.006237

Convert to g Cu(NO3)2 = 0.006237 x 187.55 = 1.16975 which rounds to 1.17g to 3 significant figures.