Difference Between Amphiprotic and Amphoteric

Main Difference – Amphiprotic vs Amphoteric

Amphoterism is the presence of amphoteric properties. Amphoteric substances are compounds that can act as both acids and bases depending on the medium. The term amphiprotic describes a substance that can both accept and donate a proton or H⁺. All amphoteric substances are amphiprotic. But all amphiprotic substances are not amphoteric; some oxides are amphoteric, but they are not amphiprotic since they cannot release or accept protons. The main difference between amphiprotic and amphoteric is that amphiprotic refers to the ability to donate or accept protons whereas amphoteric refers to the ability to act as an acid or a base.

Key Areas Covered

1. What is Amphiprotic
     – Definition, Compounds
2. What is Amphoteric
     – Definition, Compounds
3. What is the Difference Between Amphiprotic and Amphoteric
     – Comparison of Key Differences

Key Terms: Acid, Amphiprotic, Amphoteric, Amphoterism, Base, Hydronium Ion, Hydroxides, Oxides, Proton

What is Amphiprotic

In chemistry, the term amphiprotic describes a substance that can both accept and donate a proton or H⁺. An amphiprotic compound has both acidic and basic properties and can act as either as an acid or a base since an acid is a chemical species that is able to donate a proton whereas a base is a compound that can donate a hydroxyl ion (-OH) to the medium. For example, amino acids are amphiprotic molecules. This is because amino acids are composed of amine groups (basic) and carboxyl groups (acidic).

Figure 1: Amino acids are Composed of a –NH2 group and –COOH.

One of the most important amphiprotic compounds is water. When an acid donates a proton to water, water can accept that proton and form hydronium ions (H₃O⁺). When a base reacts with a water molecule, water molecule donates a proton. The amphiprotic nature refers to the ability to both donate and accept protons. Amphiprotic nature of water describes the ability of water to be amphiprotic.

What is Amphoteric

Amphoteric refers to the ability to act as both an acid and a base. The behavior of these compounds depends on the medium. Water is a good example of an amphoteric substance. Water molecules can release protons or accept protons and can act as an acid or a base. The lone pair on the oxygen atom of the water molecule helps to accept an incoming proton.

Amphoteric nature means having amphoteric properties. Most of the oxides and hydroxides are good examples of these substances. An amphoteric oxide is an oxide that can act as either an acid or a base in a reaction to produce a salt and water. Amphoterism depends on the oxidation state of atoms in the oxide or hydroxide. Since most metals have multiple oxidation states, they can form amphoteric oxides and hydroxides.

Figure 2: Zinc Oxide is an Amphoteric Oxide

For example, Zinc oxide is an amphoteric oxide. It can react with both acids and bases. When reacted with sulfuric acid, zinc oxide forms the zinc sulfate and water as the final products. When zinc oxide reacts with sodium hydroxide (aqueous), sodium zincate (Na₂[Zn(OH)₄]) is formed. When hydroxides are considered, aluminum hydroxide and beryllium hydroxide are the most common amphoteric hydroxides.

Difference Between Amphiprotic and Amphoteric

Definition

Amphiprotic: The term amphiprotic describes a substance that can both accept and donate a proton or H⁺.

Amphiprotic: The term amphoteric refers to the ability to act as both an acid and a base.

Theory

Amphiprotic: Amphiprotic substances can both accept or donate protons.

Amphiprotic: Amphoteric substances can act as both an acid and a base.

Nature

Amphiprotic: All amphoteric substances are amphiprotic.

Amphiprotic: All amphiprotic substances are not amphoteric.

Conclusion

The main difference between amphiprotic and amphoteric is that amphiprotic means the ability to donate or accept protons whereas amphoteric means the ability to act as an acid or a base. However, all amphiprotic substances are not amphoteric; some oxides are amphoteric, but they are not amphiprotic since they cannot release or accept protons.

Reference:

1. Helmenstine, Anne Marie. “Amphiprotic Definition.” ThoughtCo, Mar. 8, 2014, Available here.
2. “11.11: Amphiprotic Species.” Chemistry LibreTexts, Libretexts, 6 Sept. 2017, Available here.
3. Helmenstine, Anne Marie. “Amphoteric Definition and Examples.” ThoughtCo, May. 4, 2017, Available here.

Image Courtesy:

1. “AminoAcidball” By GYassineMrabet – created with Inkscape. – Own work (Public Domain) via Commons Wikimedia
2. “Zinc oxide sample” By Adam Rędzikowski – Own work (CC BY-SA 4.0) via Commons Wikimedia