The $\mathrm{pH}$ value of gastric juice in human stomach is about $1.8$ and in the small intestine it is about $7.8$. The $\mathrm{p} K_{a}$ value of aspirin is $3.5$. Aspirin will be

• A

  completely ionised in the small intestine and in the stomach
• B

  unionised in the small intestine and in the stomach
• C

  ionised in the small intestine and almost unionised in the stomach
• Correct answer
  D

  ionised in the stomach and almost unionised in the small intestine

Solution

Aspirin is an acidic compound. It will not dissociate in acidic medium i.e., small intestine in order to react with base but will dissociate in basic medium.

Hence, the correct answer is option: 'D'.