Final answer:
An equilibrium expression represents a balance between product and reactant concentrations at chemical equilibrium. It's written by multiplying products' concentrations over reactants',
Step-by-step explanation:
The key features of an equilibrium expression that you should be aware of are integral to understanding chemical equilibria. In a chemical reaction at equilibrium, the concentrations of reactants and products remain constant over time. The equilibrium constant expression reflects this balance and is essential for describing the system quantitatively.
To write an equilibrium constant expression, the concentrations of the products (on the numerator) are multiplied together and raised to the power corresponding to their coefficients in the balanced equation. Conversely, the concentrations of the reactants (on the denominator) are also multiplied together and raised to their respective powers.
Solids and liquids are not included in the equilibrium constant expression. If the reaction is written in reverse, the form and magnitude of the equilibrium constant change. The Law of Mass Action and learning objectives such as defining the equilibrium constant and constructing its expression are central to chemical equilibrium.