Question

Consider the following reaction: Fe + O₂ -> Fe₂O₃

Balance the equation.

If 4 g of Fe₂O₃ is produced, how much iron was there initially?

If we start with equal masses of each reactant, which reactant would be limiting? What percent of the other reactant would be left?

Answer 1

Molar mass of Fe2O3 = 159.69 g/mol

4g Fe2O3 is 4/159.69 = 0.0250 moles

2 iron atoms are needed to produce onr Fe2O3 which mean 2x moles of iron produces x moles of fe2o3.

x moles of iron produces x/2 moles of fe2o3.

so 0.0250 moles of fe2o3 is produced from 0.0250 x 2 moles = 0.05 moles of Fe =0.05*55.85 = 2.79 g

molecular mass of oxygen is less than molecular mass of Fe.

so iron will be lmiting agent.

2 moles of Fe react with 3 moles of O. let X g be the starting amount.

then we have X/16 moles of oxygen and X/55.84 moles Fe.