Question

What is the percent yield of CO2 if 80g of Fe2(CO3)3 is decomposed to yield Fe2O3 + 22g of CO2

Answer 1

80 g Fe2(CO3)2 x (2*molar mass CO2/molar mass Fe2(CO3)2) = about 30 g which is the theoretical yield of CO2. You should calculate a more exact answer.
Then %yield = (22/30)*100 = ?

Answer 2

56.1%