Kc equilibrium constants are generated using concentrations of aqueous solutions or molar volumes of gases. Brackets, [ ], are shown to indicate concentration in molarity. This is how we typically treat all equilibria constants as we are initially learning about them. Kp equilibrium constants are generated using partial pressures of gases. Equip with knowledge of the ideal gas law students know that we can use pressure and the other conditions provided to determine the number of moles of a reagent. This will cause Kc and Kp to differ in value. This exercise allows us an opportunity to differentiate between the two equilibria constants.