Question

Silver sulfide and hydrogen gas combine to form silver and hydrogen sulfide. 3.0 g of H₂ and 100 g of Ag₂S are used to produce silver. The equation for the reaction is:

 Ag₂S + H₂ -> 2Ag + H₂S

Calculate the theoretical yield of silver? Your answer needs to explain what is the limiting reagent.

Answer 1

According to the reaction one mole of hydrogen reacts with one mole of silver sulfide. The number of moles of reactants used in the reaction are:

n(H₂) = m(H₂) / Mr(H₂) = 3.0 g / 2 g/mol = 1.5 mol

n(Ag₂S) = m(Ag₂S) / Mr(Ag₂S) = 100 g / 248 g/mol = 0.4 mol

Since the reaction occurs between 0.4 mol of Ag₂S and 1.5 mol of H₂, Ag₂S is a limiting reactant. From here, the theoretical yield of silver equals:

m(Ag) = m(Ag₂S) × Mr(Ag) × 2 / Mr(Ag₂S) = 100 g × 108 g/mol × 2 / 248 g/mol = 87.1 g

Answer: 87.1 g