$K_c$: Uses molar concentrations (mol/L). $K_p$: Uses partial pressures (usually in atm).

A state where the rate of forward and reverse reactions are equal, and the concentrations of reactants and products remain constant.

Equilibrium constant in terms of concentration; relates the concentrations of reactants and products at equilibrium.

Equilibrium constant in terms of pressure; relates the partial pressures of gaseous reactants and products at equilibrium.

Product-favored reaction. At equilibrium, there are more products than reactants.

Reactant-favored reaction. At equilibrium, there are more reactants than products.

The amount of reactants and products are roughly equal at equilibrium.

1. Write the $K_c$ expression. 2. Calculate equilibrium concentrations. 3. Plug the concentrations into the $K_c$ expression.

1. Write the $K_p$ expression. 2. Plug in the partial pressures.