Na2S solution was added to 27g solution with mass fraction (CuCl2) = 10%. Determine the mass of the precipitated sediment.

CuCl2 + Na2S = CuS + 2NaCl.
The sediment is copper sulfide.
1) According to the formula W = (mr.v. – wa / mr – pa) * 100% we find the mass of the solute of copper chloride in its solution: 10 * 27/100 = 2.7 g.
2) The molar mass of copper chloride is: 134.
3) The amount of copper chloride substance is: 2.7 / 134 = 0.02 mol.
4) The amount of copper chloride substance is equal to the amount of copper sulfide substance (according to the reaction equation) and is equal to 0.02 mol.
5) Molar mass of sediment: 96.
6) The mass of the sediment is: 0.02 * 96 = 1.92 g – the answer.