The `pK_(a)` of acteylsalicylic acid (aspirin) is `3.5`. The pH of gastric juice in human stomach is about `2-3` and the pH in the small intestine is about 8. Aspirin will be:

Options

A. completely ionizzed in the small intestine and in the stomach
B. ionized in the small intestine and almost uniozed in the stomch
C. ionized in the stomach and almost unionized in the small intestine
D. unionized in the small intestine and in the stomach

Answer

B

Explanation

Acetyl salicylic acid is a weak monoprotic acid. Therefore, its ionization equilibrium can be described as
`HA(aq.)hArrH^(+)(aq.)+A^(-)(aq.)`
The medium in the stomach is quite acidic. Thus, due to common ion effect of `H^(+)` ions, aspirin is almost unionized in stomach. The medium in the small intestine is alkaline. Thus, the `OH^(-)` ions present over there react with `H^(+)` ions (to form `H_(2)O)` and shift the ionization equilibrium toward right.