Question

The pKa of acetylsalicylic acid (aspirin) is 3.5. The pH of gastric juice in the human stomach is about 2 to 3 and pH in small intestine is about 8 . Aspirin will be a. unionized in the small intestine and in the stomach b. compeletly ionised in the small intestine and in the stomach c. ionized in the stomach and almost unionised in the small intestine d. ionised in the small intestine and almost unionised in the stomach. Please explain briefly with reason:

Answer 1

Asprin being an acidic compound will not dissociate in acidic medium however it will dissociates in basic medium i.e small intestine in order to react with base  which results in the formation of dissociated aspirin & water.
Hence the correct option is D.
However,this can also be explained on the basic of common ion effect.As the number of H+ Ions in acidic medium are more therefore the reaction moves backward in agreement of le Chaterlier principle & hence does not dissociate.