Bronsted Lowry Acids and Bases | Conjugate acid & Conjugate Base| Amphoteric Compounds| Limitations

Summary

In this video, the Bronsted-Lowry theory of acids and bases is explained, focusing on proton transfer. An acid is a substance that donates a proton (H+), while a base accepts one. The concept of conjugate acids and bases is introduced, with examples like HCl and water. Amphoteric compounds, such as water, can act as both acids and bases depending on the reaction. The theory is also discussed in terms of reactions involving substances like ammonia and acetic acid. However, the theory has limitations, as certain substances behave as acids or bases without following the proton transfer rule.

Takeaways

• 😀 The Bronsted-Lowry theory of acids and bases, proposed in 1923, is based on proton transfer.
• 😀 According to the Bronsted-Lowry theory, an acid is a substance that can donate a proton (H+), while a base can accept a proton.
• 😀 A proton is simply a hydrogen ion (H+) that has lost its electron, making it a positively charged ion.
• 😀 An example of the Bronsted-Lowry theory in action: When HCl dissolves in water, HCl acts as an acid (donating a proton), and water acts as a base (accepting the proton).
• 😀 In the reverse reaction, chloride ion acts as a base, while hydronium ion (H3O+) acts as a conjugate acid.
• 😀 Every acid produces a conjugate base, and every base produces a conjugate acid.
• 😀 'Conjugate' refers to compounds formed by combining two or more chemicals, with conjugates acting as opposites in acid-base reactions.
• 😀 Amphoteric compounds can act as both acids and bases, depending on the circumstances. Water is an example of an amphoteric compound.
• 😀 In the example of ammonia reacting with water, ammonia acts as a base (accepting a proton) and water acts as an acid (donating a proton).
• 😀 Despite the significance of the Bronsted-Lowry theory, it has limitations, as certain substances act as acids or bases without donating or accepting protons, such as sulfur dioxide and calcium oxide.

Q & A

What is the Bronsted-Lowry theory of acids and bases?

The Bronsted-Lowry theory, presented in 1923 by Danish chemist Bronsted and English chemist Lowry, defines acids as substances that donate a proton (H+ ion) to another substance, and bases as substances that accept a proton.

How does the Bronsted-Lowry theory define acids and bases?

An acid is a substance that can donate a proton (H+ ion) to another substance, while a base is a substance that can accept a proton from another substance.

What is a proton in the context of Bronsted-Lowry theory?

A proton is essentially a hydrogen ion (H+), which is a hydrogen atom that has lost its electron. It is often used interchangeably with H+ in acid-base reactions.

Can you explain the concept of conjugate acids and bases?

In the Bronsted-Lowry theory, a conjugate base is formed when an acid donates a proton, and a conjugate acid is formed when a base accepts a proton. For example, when hydrochloric acid (HCl) donates a proton, it forms chloride ion (Cl-) as its conjugate base, and water (H2O) that accepts a proton becomes hydronium ion (H3O+) as the conjugate acid.

What is meant by amphoteric compounds?

Amphoteric compounds are substances that can act as both acids and bases depending on the conditions. Water is a classic example, as it can donate a proton (acting as an acid) or accept a proton (acting as a base).

Can you give an example of an amphoteric compound?

Water (H2O) is an example of an amphoteric compound. It can act as an acid when it donates a proton to a base, or it can act as a base when it accepts a proton from an acid.

What happens when acetic acid reacts with water?

When acetic acid reacts with water, acetic acid donates a proton to water, forming acetate ion (CH3COO-) and hydronium ion (H3O+). In this reaction, acetic acid acts as an acid, and water acts as a base.

How does ammonia interact with water in the Bronsted-Lowry theory?

In the reaction between ammonia (NH3) and water, ammonia accepts a proton from water, forming ammonium ion (NH4+) and hydroxide ion (OH-). Ammonia acts as a base, while water acts as an acid.

What is a key limitation of the Bronsted-Lowry theory?

A key limitation of the Bronsted-Lowry theory is that it does not account for substances like sulfur dioxide, which behave as acids but do not donate protons. Similarly, calcium oxide behaves as a base but cannot accept a proton.

Why is water considered an amphoteric compound?

Water is considered an amphoteric compound because it can act both as an acid, donating a proton, and as a base, accepting a proton, depending on the substances it reacts with.