Aspirin is a weak acid as shown below that is taken up into the bloodstream by diffusion through cells lining the stomach and the small intestine.
Aspirin crosses the plasma membrane of a cell most effectively in its uncharged (protonated) form; in its charged (deprotonated) form it cannot cross the hydrophobic lipid bilayer of the membrane.
The pH of the stomach is about 1.5 and that of the lumen of the small intestine is about 6.0. Is the majority of the aspirin absorbed in the stomach or in the intestine? Explain you reasoning.