10 grams of lime stone on calcination produced 4.2 grams of calcium oxide. Percentage yield of calcium oxide is equal to

CaCO3s →∆ CaOs+CO2g;  100 g                    56 g    10 g                   5.6 g ; If the yield is 100% then the weight of CaO obtained =5.6 g ; but the weight of CaO obtained is 4.2 g; Thus percentage yield of CaO=4.25.6×100=75% ;