equilibrium constant

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equilibrium constant

chemistry

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June 26, 2026

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In chemistry, the equilibrium constant is a numerical value that expresses the relationship between the amounts of products and reactants present at equilibrium in a reversible chemical reaction at a specific temperature. Chemical equilibrium is a state in a reversible reaction where the rates of the forward and reverse reactions are equal, resulting in no net change in the amounts of reactants and products.12

The equilibrium constant, often denoted as K_c, is calculated as the ratio of the concentrations of products to reactants, each raised to their respective stoichiometric coefficients. A large K_c value indicates that products predominate at equilibrium, while a small value suggests reactants are favored. The value of the equilibrium constant is dependent on temperature and pressure, and changes in these conditions will shift the equilibrium according to Le Chatelier's principle.2

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acid–base reaction
Acid–base equilibria
The equilibrium constant (also called ionization constant, K_s′) for this reaction (the mathematical quantity that expresses the relationships between the concentrations of the various species present at equilibrium) would normally be given by the equation K_s′ = [SH₂⁺] [S⁻]/[SH]², in which the square brackets denote the…
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The equilibrium constant (also called ionization constant, K_s′) for this reaction (the mathematical quantity that expresses the relationships between the concentrations of the various species present at equilibrium) would normally be given by the equation K_s′ = [SH₂⁺] [S⁻]/[SH]², in which the square brackets denote the…
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coordination compound
Aqua complexes
…chelation is reflected in the equilibrium constants of the reactions—values that indicate the relative proportions of the starting materials and the products at equilibrium. Complexes of hexaaquanickel(2+) ions can be formed with a series of polyamines—i.e.,
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…chelation is reflected in the equilibrium constants of the reactions—values that indicate the relative proportions of the starting materials and the products at equilibrium. Complexes of hexaaquanickel(2+) ions can be formed with a series of polyamines—i.e.,
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ion-exchange reaction
Ion-exchange equilibria
…present under the conditions of equilibrium:
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…present under the conditions of equilibrium:
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isotope
Chemical effects of isotopic substitution
Special quantities called chemical equilibrium constants express in quantitative terms the extent to which a chemical reaction favours products (the substances written to the right of the arrow) or reactants (the substances written to the left of the arrow). For reactions of the type cited, which chemists call exchange…
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Special quantities called chemical equilibrium constants express in quantitative terms the extent to which a chemical reaction favours products (the substances written to the right of the arrow) or reactants (the substances written to the left of the arrow). For reactions of the type cited, which chemists call exchange…
Read More