what mass of aluminum hydroxide needs to be consumed to neutralize 1.25L of stomach acid (HCl). Stomach acid has a pH of 2.2

Answer 1

pH = -log(H^+)
-2.2 = log(H^+) and
(H^+) = 0.00631 M
molsl H^+ = M x L = 0.00631 x 1.25 L = aboaut 0.008 but you need to that more accurately.
Al(OH)3 + 3HCl = AlCl3 + 3H2O

mols HCl = about 0.008
Convert mols HCl to mols Al(OH)3 using the coefficients in the balanced equation. That will give you 0.008 x 1/3 = mols Al(OH)3.
Convert that to grams. g = mols x molar mass.