If 75.0 g of silderite ore is heated with an excess of oxygen, 45.0 g of ferric oxide is produced. what is the percent yield of this reaction?

The chemical reaction for this is expressed as:
 4FeCO3 + 4O2 > 4FeO3 + 4CO2

We are first need to calculate the theoretical amount of ferric oxide that whould be obtain from the given amount of ore. We do as follows:

75 g FeCO3 ( 1 mol / 116 g ) ( 4 mol FeO3 / 4 mol FeCO3 ) ( 103.84 g / mol ) = 67.14 g FeO3 theoretically produced

Percent yield = actual mass / theoretical mass x 100 = 45 / 67.14 x 100 = 67.03%