Here is some pure water, which has a pH of 7, shown by using this testing paper and matching the color to the chart on the side of the box.
If I take a straw and blow into the water, what gases are going into the water?
The one I am interested in is carbon dioxide, which can dissolve in water and react to form an acid.
CO2(g) + H2O(l) H2CO3(aq)
H+(aq) + HCO3‑(aq)
So after I blow into the water several times, I should have a solution which is more acid than it was before. Let's check by retesting the pH of the solution. It is now down to 5, rather than the 7 it was as pure water. pH 5 is an acid, so the carbon dioxide has dissolved in the water and reacted.
Thus my chemical reaction really has made hydrogen ions in the water, meaning that the carbon dioxide gas dissolved and reacted.
CO2(g) + H2O(l) H+(aq) + HCO3‑(aq)
What does this mean about rain which passes through air with CO2 in it ?
