system
Given the following post, respond as if you're commenting on Reddit:
human
If you were stranded in the desert and all you had was a bottle of Tums...

I'm learning about acids and bases in Chemistry right now and one of the most common examples of how to tame an acid is taking antacid tablets (such as Tums which is Calcium Carbonate). These tablets will turn the HCl in our stomachs (which causes heartburn) into water (and salt). My question is, if you were stranded in the desert with no water, but happened to have a  bottle of tums, would the water produced in the reaction be sufficient enough to keep you from becoming dehydrated too quickly?
gpt
No. Gastric acid is partly produced from the reaction: CO2 + H2O -> H2CO3 -> H+ + HCO3-. The neutralization of the acidic protons in stomach acid with antacid would produce bicarbonate, which can be converted back into water and carbon dioxide by carbonic anhydrase. In other words, this is the opposite reaction of the above, and the net reaction yields no excess, "new" water.

edit: also, stomach pH is homeostatically regulated, so the increased gastric pH by antacid consumption will cause the production of more gastic acid, which will probably wipe out any potential gain in net water by the neutralization reaction.