For ambient air, "P"CO2 is around atmospheres (or equivalently 35 Pa). The last equation above fixes the concentration of dissolved CO2 as a function of "P"CO2, independent of the concentration of dissolved CaCO3. At atmospheric partial pressure of CO2, dissolved CO2 concentration is moles per liter. The equation before that fixes the concentration of H2CO3 as a function of CO2 concentration. For = , it results in [H2CO3 = moles per liter. When [H2CO3] is known, the remaining three equations together with