Equilibrium expression

Definition

The equilibrium expression is an equation that represents the ratio of product concentrations to reactant concentrations at a given point in time during a reversible chemical reaction. It is used to calculate the value of the equilibrium constant (K) for the reaction.

Related terms

K (equilibrium constant): K is a numerical value that indicates whether a reaction favors the formation of products or reactants at equilibrium. It is calculated by using the concentrations (or partial pressures) of products and reactants raised to their stoichiometric coefficients.

Le Chatelier's Principle: This principle states that when a system at equilibrium is subjected to external stress, it will shift its position in order to counteract that stress and restore equilibrium. The stress can be changes in concentration, pressure, or temperature.

Reaction Quotient (Q):

Q is similar to K but it is calculated using any set of concentrations or partial pressures at any point during a reaction, not just at equilibrium. By comparing Q with K, we can determine if a system has reached its equilibrium state yet.