Equilibrium Constant (Keq)

Definition

This number expresses the relationship between concentrations of products and reactants at equilibrium for a particular reaction at constant temperature.

Analogy

Consider Keq as an impartial referee in a tug-of-war game between two teams - reactants and products. When both sides are pulling equally hard so no team moves anymore, we say they've reached equilibrium. The ratio of the strengths (concentrations) of both teams is represented by Keq.

Related terms

Le Chatelier's Principle: A principle stating that if a change in conditions is imposed on a system at equilibrium, the system will adjust itself to partially counteract the change.

Reaction Quotient (Q): A measure similar to Keq but for non-equilibrium conditions. It helps predict which direction a reaction will proceed to reach equilibrium.

Chemical Equilibrium: The state where concentrations of reactants and products remain constant over time because their rates of reaction are equal.