Final answer:
The equilibrium constant for the given reaction involving iron, water vapor, iron oxide, and hydrogen is based on the gaseous reactants' and products' concentrations, with pure solids assigned a value of 1. The constant is calculated without considering solid reactant and product concentrations.
Step-by-step explanation:
Defining Equilibrium Constant for a Chemical Reaction
The equilibrium constant for the reaction 3Fe (s) + 4H₂O (g) → Fe₃O₄ (s) + 4H₂(g) is determined by the concentrations of the reactants and products when the reaction has reached equilibrium. In this reaction, since Fe₃O₄ and Fe are both pure solids, they are each assigned a value of 1 in the equilibrium constant expression. Therefore, the equilibrium constant expression for this reaction is K = [H₂]4 / [H₂O]4, with the concentration of the gaseous species raised to the power of their coefficients in the balanced equation. It's important to note that for the reactions mentioned, Fe(s) oxidizes to Fe²+(aq) in the presence of O₂(g) and H+(aq), forming Fe²+(aq) and H₂O(l). Different iron compounds, like Fe(OH)3 and Fe₃O₄, are formed depending on the reaction conditions. Understanding these chemical principles is crucial in fields such as corrosion science and electrochemistry.