The following diagrams represent two similar reactions that have achieved equilibrium: <.> Write the expression for the equilibrium constant for each reaction.

The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given chemical reaction. It is calculated using the formula K = [products]^[coefficients] / [reactants]^[coefficients], where the brackets denote concentration and coefficients are the stoichiometric coefficients from the balanced equation. A large K value indicates a reaction that favors products, while a small K value suggests a preference for reactants.

Dynamic equilibrium occurs in a reversible reaction when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products over time. This state does not imply that the reactions have stopped; rather, they continue to occur at equal rates. Understanding dynamic equilibrium is crucial for writing equilibrium expressions, as it highlights the balance between reactants and products.

Stoichiometry refers to the relationship between the quantities of reactants and products in a chemical reaction, which is represented by the coefficients in a balanced equation. When writing equilibrium expressions, the coefficients are used as exponents in the expression for K. This concept is essential for accurately determining the equilibrium constant, as it reflects the proportions of substances involved in the reaction.