Chapter 9, Problem 71AP

When elemental copper is strongly heated with sulfur, a mixture of CuS and ${\text{Cu}}_2\text{S}$is produced. with CuS predominating.

:math> Cu ( s ) + S ( s ) → CuS ( s ) 2 Cu ( s ) + S ( s ) → Cu 2 S ( s )

at is the theoretical yield of CuS when 31.8 g of Cu(s) is heated with 50.0 g of S? (Assume only CuS is produced in the reaction.) What is the percent yield of CuS if only 40.0 g of CuS can be isolated from the mixture?