Simplified carbonic acid system

If one has to perform calculations in the carbonic acid system, one tries to make the system clearer and simplifies it. One omits the specification of the carbonic acid itself, since it is present only in very small concentrations in the water. The reaction equation is presented as if hydrogen carbonate is formed directly from CO 2 and water. To keep the calculations accurate anyway, the two mass action constants of the initial reactions are combined into a new one. The expanded CO 2 is used here without index. I

Also in this simplified carbonic acid system, the carbonic acid forms can be summarized in one equation.

The carbonic acid forms are present in different proportions in the water. How large the proportions are depends solely on the pH value (H + ) of the water. If the pH is low, i.e. there are many H + ions in the water, the reaction equilibrium is shifted completely to the left, there is predominantly CO 2 in the water, little hydrogen carbonate and virtually no carbonate. If the pH is high, i.e. there are few H + ions in the water, the reaction equilibrium is shifted to the far right, there is predominantly carbonate in the water, little hydrogen carbonate and virtually no CO 2 . In the medium pH range, hydrogen carbonate predominates and the proportions of CO 2 and carbonate are low.