Amphiprotic Species
- Species that can act both as proton donors and acceptors are called amphiprotic
Water as a Brønsted-Lowry acid
Diagram to show how water is amphiprotic
The diagram shows water acting as a Brønsted-Lowry acid by donating a proton to ammonia which accepts the proton using its lone pair of electrons
Lewis diagram for the reaction between water and ammonia
The Lewis diagram for the reaction of water with ammonia to show how water acts as a Brønsted-Lowry acid and ammonia as a Brønsted-Lowry base
Water as a Brønsted-Lowry base
Diagram to show how water is amphiprotic
The diagram shows water acting as a Brønsted-Lowry base by accepting a proton from hydrochloric acid proton using its lone pair of electrons
Lewis diagram for the reaction between water and hydrochloric acid
The Lewis diagram for the reaction of water with hydrochloric acid to show how water acts as a Brønsted-Lowry base and ammonia as a Brønsted-Lowry acid
What is the difference between amphiprotic and amphoteric?
- A compound that is amphoteric means it has both basic and acidic character
- When the compound reacts with an acid, it shows that it has basic character
- When it reacts with a base, it shows that it's acidic
- An example of this is aluminium oxide which reacts with both hydrochloric acid and sodium hydroxide:
Al2O3 (s) + 6HCl (aq) → 2AlCl3 (aq) + 3H2O (l)
Al2O3 (s) + 2NaOH (aq) + 3H2O (l) → 2NaAl(OH)4 (aq)
- When a compound is amphiprotic, it means it can act as a proton donor and as a proton acceptor
- Aluminium oxide is not amphiprotic, even though it is amphoteric
Amphiprotic versus Amphoteric Table
| Amphiprotic | Amphoteric |
| The term amphiprotic describes a substance that can both accept and donate a proton or H+ | The term amphoteric refers to the ability to act as both an acid and a base |
| Amphiprotic substances can both accept or donate protons | Amphoteric substances can act as both an acid and a base |
| All amphiprotic substances are amphoteric | Not all amphoteric substances are amphiprotic |