Editing Chemical reaction (section)

==Chemical equilibrium==
{{Main|Chemical equilibrium}}
Most chemical reactions are reversible; that is, they can and do run in both directions. The forward and reverse reactions are competing with each other and differ in [[Chemical kinetics|reaction rates]]. These rates depend on the concentration and therefore change with the time of the reaction: the reverse rate gradually increases and becomes equal to the rate of the forward reaction, establishing the so-called chemical equilibrium. The time to reach equilibrium depends on parameters such as temperature, pressure, and the materials involved, and is determined by the [[Principle of minimum energy|minimum free energy]]. In equilibrium, the [[Gibbs free energy]] of reaction must be zero. The pressure dependence can be explained with the [[Le Chatelier's principle]]. For example, an increase in pressure due to decreasing volume causes the reaction to shift to the side with fewer moles of gas.<ref>[[#Atkins|Atkins]], p. 114.</ref>

The reaction yield stabilizes at equilibrium but can be increased by removing the product from the reaction mixture or changed by increasing the temperature or pressure. A change in the concentrations of the reactants does not affect the equilibrium constant but does affect the equilibrium position.