Hi,how long does amoxicillin treat acid stomach?

Amoxicillin does not work on stomach acid directly. It's an antibiotic. Those with stomach ulcers, often have simultaneous infection with H.Pylori,(now believed to be a culprit related the the problem). So Amoxicillin may be used to help get rid of H. Pylori. Often patients are given another medicine, either a class of H2 blocker (like pepcid) or proton pump inhibitor (ie. omeprazole) for acid.