Acid–base Equilibria

Question

Which factor most strongly determines whether an amphoteric species acts as an acid or a base in water?

RankGuru · Accepted Answer

1. **Amphoteric Definition**: A species that can either donate or accept a proton (e.g., $H_2O, HCO_3^-$).
2. **Behavior Control**: Their action depends on the **relative strength** of other components in the environment.
3. **Examples**:
   - In the presence of a strong acid ($HCl$), $HCO_3^-$ acts as a base ($HCO_3^- + H^+ 	o H_2CO_3$).
   - In the presence of a strong base ($OH^-$), $HCO_3^-$ acts as an acid ($HCO_3^- + OH^- 	o CO_3^{2-} + H_2O$).
4. **Conclusion**: The **external chemical environment** dictates the role of an amphoteric substance.

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Acid–base Equilibria

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