Question

If 1.2 moles of CuCl are mixed with excess of H2S gas, how many moles of Cu2S would be made?

Answer 1

Moles of CuS : 1.2

Further explanation

The reaction coefficient in a chemical equation shows the mole ratio of the components of the reactants and products

If one mole of the reactant or product is known, then we can determine the moles of the other compounds involved in the reaction

Reaction

CuCl₂ (aq) + H₂S (g) → CuS (s) + 2HCl (aq)

CuCl are mixed with  excess of H₂S gas, so CuCl as a limiting reactant

mol ratio of CuCl₂ : mol CuS = 1 : 1, so mol CuS :

$\tt =\dfrac{1}{1}\times 1.2=1.2~moles$