Equilibrium constant

Equilibrium Constant is a fundamental concept in the field of Chemistry, specifically in the study of Chemical Equilibrium. It is a measure of the ratio of the concentrations of products to reactants at equilibrium, with each concentration raised to the power of its stoichiometric coefficient in the balanced chemical equation.

Definition

The Equilibrium Constant (symbol: K) is defined for a general chemical reaction:

aA + bB ⇌ cC + dD

The equilibrium constant expression is given by:

K = ([C]^c [D]^d) / ([A]^a [B]^b)

where [A], [B], [C], and [D] represent the molar concentrations of the chemicals A, B, C, and D respectively, at equilibrium. The coefficients a, b, c, and d are the stoichiometric coefficients of the balanced chemical equation.

Types of Equilibrium Constants

There are several types of equilibrium constants, each used for different types of reactions:

• Kc - used for reactions in which concentrations are expressed in molarity.
• Kp - used for reactions involving gases, where concentrations are expressed in terms of partial pressures.
• Ka and Kb - used for acid-base reactions.
• Kw - the ion product of water.
• Ksp - the solubility product constant.

Factors Affecting the Equilibrium Constant

The value of the equilibrium constant is temperature dependent. Changes in pressure, concentration, or the addition of a catalyst do not affect the value of the equilibrium constant, although they do affect the position of the equilibrium.

See Also

• Le Chatelier's Principle
• Chemical Equilibrium
• Reaction Rate

References

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