Equilibrium constant, K

Definition

The equilibrium constant, $K$, is a ratio that quantifies the concentrations of reactants and products in a chemical reaction at equilibrium. It provides insight into the position of the equilibrium and the extent to which reactants are converted into products.

5 Must Know Facts For Your Next Test

1. The value of $K$ is temperature-dependent; it changes with temperature.
2. For a reaction: $aA + bB \rightleftharpoons cC + dD$, the equilibrium constant expression is given by $K = \frac{[C]^c[D]^d}{[A]^a[B]^b}$.
3. $K > 1$ indicates that products are favored at equilibrium, while $K < 1$ indicates that reactants are favored.
4. Pure solids and liquids do not appear in the expression for $K$; only aqueous and gaseous species are included.
5. $K_p$ is used for reactions involving gases and relates to partial pressures, whereas $K_c$ relates to molar concentrations.

Review Questions

• What does it mean if an equilibrium constant, $K$, is greater than 1?
• How does temperature affect the value of an equilibrium constant, $K$?
• Write the general form of an equilibrium constant expression for a given balanced chemical equation.

Related terms

$Le \ Chatelier's \ Principle$: States that if a dynamic equilibrium is disturbed by changing conditions, the position of equilibrium moves to counteract the change.

$Reaction \ Quotient \ (Q)$: Calculates the ratio of product concentrations to reactant concentrations at any point during a reaction before reaching equilibrium.

$Dynamic \ Equilibrium$: Occurs when the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in concentrations of reactants and products.