Solid calcium carbonate () decomposes into solid calcium oxide () and gaseous carbon dioxide () in a constant-volume container at high temperatures. Carbon dioxide is assumed to be an ideal gas, and the two solids are assumed to be in separate phases. You can vary the number of moles of , , and added to the constant-volume container using sliders. The container displays the equilibrium pressure; the color intensity of the gas phase increases as the number of moles of increases. The bar graph on the right shows the number of moles present at equilibrium. The equilibrium constant changes as the temperature changes using the slider. The equilibrium constant is equal to the pressure (in bar) divided by the standard-state pressure of 1 bar. Note that adding more when is already in the container (or adding more when is already in the container) at equilibrium does not change equilibrium because increasing the number of moles of a pure solid does not change its fugacity.