How much zinc sulfide is formed when 15.6 g of sodium sulfide reacts with an excess of zinc chloride?

The reaction equation for the interaction of sodium sulfide with zinc chloride:

Na2S + ZnCl2 = 2NaCl + ZnS

The amount of Na2S substance:

v (Na2S) = m (Na2S) / M (Na2S) = 15.6 / 78 = 0.2 (mol).

According to the reaction equation, from 1 mol of Na2S, 1 mol of ZnS is formed, therefore:

v (ZnS) = v (Na2S) = 0.2 (mol).

Mass of zinc sulfide formed:

m (ZnS) = v (ZnS) * M (ZnS) = 0.2 * 97 = 19.4 (g).