Final answer:
The Kc equilibrium-constant expression is a ratio of the concentrations of the products to the reactants at equilibrium for a chemical reaction. The provided reference explains how to calculate this using an example, emphasizing the importance of significant figures in these calculations.
Step-by-step explanation:
The student is asking for the Kc equilibrium-constant expression for a given chemical equilibrium. The Kc expression is the ratio of the concentrations of the products raised to the power of their coefficients to the concentrations of the reactants raised to the power of their coefficients in a balanced chemical equation at equilibrium. This can be derived from the Law of Mass Action.
In the context provided, it is implied that the student should construct the equilibrium expression for a specific reaction. The coefficients and reactants/products would be needed for the exact expression. An example of how Kc is calculated is provided in the reference, where the equilibrium constant expressions for K1 and K2 are multiplied to get K3 as K3 = K1 * K2. Similarly, you would use the equilibrium concentrations of the reactants and products to calculate Kc for the given reaction. Furthermore, the importance of using significant figures and making approximations in assumptions about the magnitude of x is highlighted.