Question

The $p{K}_a$ of acetyl salicylic acid (aspirin) is 3.5. The pH of gastric juice in human stomach is around 2 and the pH in small intestine is around 8. Aspirin will be

• A. unionized in stomach as well as in intestine
• B. ionized in stomach as well as in intestine
• C. unionized in stomach but ionized in intestine
• D. ionized in stomach but unionized in intestine

Answer 1

Answer: (C)

: Aspirin is a weak monoprotic acid. In the stomach, the medium is acidic while in the small intestine, the medium is basic. Hence acetyl salicylic acid is almost unionized in stomach but ionized in the small intestine.