Final answer:
In the given reaction, 4 molecules of hydrogen gas are produced when iron reacts with water vapor, as determined by the balanced chemical equation.
Step-by-step explanation:
According to the balanced chemical equation 3Fe + 4H₂O → Fe₃O₄ + 4H₂, 4 molecules of H₂ (hydrogen gas) are produced.
The provided chemical equation represents a reaction where iron (Fe) reacts with water vapor (H₂O) to form iron(II,III) oxide (Fe₃O₄) and hydrogen gas (H₂). This type of reaction is known as a synthesis reaction, where multiple reactants combine to form a single product. Stoichiometry allows us to understand the proportions in which reactants combine and in which products are formed. In this equation, it is indicated that 3 moles of iron react with 4 moles of water vapor to produce 1 mole of iron oxide and 4 moles of hydrogen gas.
This means that for every 3 atoms of iron reacting, 4 molecules of H₂ are produced. Therefore, if this reaction were to proceed to completion with sufficient reactants, one would expect to obtain 4 molecules of hydrogen gas for each stoichiometric batch based on the balanced equation.