The key practical steps in finding an equilibrium constant are as follows:

• Mix known amounts of reactants or products.
• Leave the mixture until an equilibrium is established.
• Find the concentration of one of the subtances in the mixture.
• Work out the concentrations for all of the components of the equilibrium mixture.
• Write a balanced equation for the reaction.
• Write down an expression for K_c.
• Substitute the equilibrium concentrations into the expression for K_c.