Question

The pH in your stomach varies considerably depending on whether or not food is being actively digested. During digestion, stomach pH typically ranges from 1-2, while resting pH generally ranges from 3-4. Antacids are a class of medicines which help neutralize stomach pH, particularly for those who might experience acid reflux. A common chemical component of antacids is aluminium hydroxide – Al(OH)₃, a single molecule of which can neutralize 3 free hydrogens. Assume that each dose of your antacid medicine contains 300mg of aluminium hydroxide (MW = 78 g/mol) and that the volume of your stomach is 0.90L.

Part A) Let’s say that after you’ve eaten you know that the pH in your stomach is 1.50 and that you will experience acid reflux until the pH in your stomach is at least 4.0. How many doses of antacid would you need to take in order to raise your pH to or above 4.0 (assume you can only take full doses – no partial doses)?

Part B) Assuming that the antacid has a clearance rate from the stomach of 1 mM/hr and that stomach acid (H⁺) is produced at a rate of 0.5 mM/hr, and that you took one more dose of antacid than you needed to get your stomach pH above 4 (add 1 to your previous answer), for how long will the antacid you took keep your stomach pH above 4? Assume steady state clearance of the antacid