The equilibrium constant, K_c, can be determined by substituting the corresponding values into the equilibrium constant expression if the concentrations of all the reactants and products at equilibrium are known.

A gaseous mixture of sulfur dioxide and oxygen at 530 °C is allowed to react according to the reaction shown. At equilibrium, the mixture contains 0.10 molar of sulfur dioxide, 0.15 molar of oxygen, and 10.88 molar of sulfur trioxide. 

By substituting the values into the equilibrium expression, the K_c equals 7.9 × 10⁴. 

The K_c can also be calculated as long as the initial concentration of all of the components and the equilibrium concentration of at least one compound is known.

The unknown equilibrium concentrations can then be calculated using the reaction stoichiometry. An ICE table is used to organize the information for the initial, change, and equilibrium concentrations of the reaction.

When a reaction mixture containing 0.11 molar nitrogen and 0.36 molar hydrogen is allowed to reach equilibrium at 500 °C, it produces 0.020 molar ammonia at equilibrium. To calculate the K_c, the equilibrium concentrations of the nitrogen and hydrogen need to be determined.

The stoichiometry of the reaction shows that 1 mole of nitrogen gas and 3 moles of hydrogen gas are required to produce 2 moles of ammonia gas.

The change, x, when multiplied by the coefficients of the reactants and products, denotes the concentration of the reactants consumed and the concentration of the product produced to reach equilibrium. 

Since 2x equals 0.020, x equals 0.010. The equilibrium concentration of nitrogen and hydrogen can then be determined by subtracting the respective concentration change from their initial concentration which equals 0.10 and 0.33 molar, respectively.

Substituting equilibrium concentrations in the K_c expression, the K_c equals 0.11.

The K_p for reactions involving gases can be calculated using an ICE table and the equilibrium expression written with partial pressures.