How can you tell

[Laila Alkhouri 3H]

How do amphoteric compounds exhibit both acidic and basic characteristics? I am having a hard time to wrap my mind around this. Sometimes I feel like it is clearer to see one of the characteristics and not the other.

[Brandon Li]

Here is an example of an amphoteric compound: HCO3- (bicarbonate ion)

One way to tell that it is an amphoteric compound is by finding if the compound is a conjugate acid and base (which means it must be able to act as either an acid or base). In the case of HCO3-, it is the conjugate base (removing a proton) of H2CO3 but also the conjugate acid of CO3 2- (adding a proton), which makes it amphoteric.