Question

How do the components of a conjugate acid-base pair differ from one another? Give an example of a conjugate acid-base pair to illustrate your answer.

Short answer

The components of a conjugate acid-base pair differ from one another in the presence or absence of an extra proton (H+ ion). The conjugate acid has one more proton than the conjugate base, while the conjugate base has one fewer proton than the conjugate acid. They are related by a proton exchange in an acid-base reaction. A common example is the relationship between ammonia (NH₃, base) and ammonium (NH₄⁺, conjugate acid), where ammonium has one more proton than ammonia.

Step-by-step solution

Identifying 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 (H+ ion) from another substance. In a chemical reaction involving an acid and a base, a conjugate acid is formed from the base and a conjugate base is formed from the acid.

Differences between conjugate acid-base pairs

The components of a conjugate acid-base pair differ from one another in the presence or absence of an extra proton (H+ ion). The conjugate acid has one more proton than the conjugate base, while the conjugate base has one fewer proton than the conjugate acid. They are related by a proton exchange in an acid-base reaction.

Providing an example of a conjugate acid-base pair

A common example of a conjugate acid-base pair is the relationship between ammonia (NH₃) and ammonium (NH₄⁺). In this example, ammonia (NH₃) is the base because it can accept a proton (H+ ion) from another substance. When ammonia accepts a proton, it forms the conjugate acid ammonium (NH₄⁺). Here, ammonium has one more proton than ammonia, which highlights the difference between conjugate acid and base pairs.

Key concepts

Acid-Base Reaction

An acid-base reaction is a fundamental chemical process in which an acid and a base interact with each other. This interaction typically results in the transfer of a proton $H^{+}$, leading to the formation of water in many cases, or other species if water isn’t involved.

The concept of acid-base reactions revolves around the idea of proton transfer. According to the Brønsted-Lowry definition, an acid is a species capable of donating a proton, while a base is capable of accepting a proton. These reactions are integral to a wide variety of chemical processes from biological systems to industrial applications.

In the course of the reaction, the acid donates a proton to the base. This transformation creates what are known as conjugate acid-base pairs. From the base receiving the proton, a conjugate acid results, and from the acid donating the proton, a conjugate base remains. This simultaneous transformation ensures the balancing of charges within the reaction.

Proton Transfer

Proton transfer is a key mechanism in acid-base chemistry, representing the movement of a proton from an acid to a base. This process is what defines the creation of conjugate acid-base pairs.

In essence, during an acid-base reaction, the acid will donate a proton $H^{+}$ to a base. Consequently, the original acid transforms into its conjugate base, which is simply the acid missing a proton.

Meanwhile, the base, having accepted the proton, is transformed into its conjugate acid. This proton exchange is critical in understanding how substances like ammonia and ammonium interrelate. It helps to visualize that acids and bases are not static but are dynamic partners in chemical reactions that depend heavily on their ability to transfer protons readily.

Ammonia and Ammonium Example

The ammonia and ammonium example is a classic illustration of a conjugate acid-base pair. In this case, ammonia $(N{H}_3)$ acts as a base.

When ammonia accepts a proton, it is transformed into ammonium $(N{H}_4^{+})$. This proton transfer changes the chemical identity from a neutral ammonia molecule into a positively charged ammonium ion.

This transaction is crucial to grasp because it labels ammonia as the base due to its proton accepting ability, while ammonium, which now has one more proton than ammonia, is designated as the conjugate acid.

• A base accepts a proton to become a conjugate acid.
• An acid donates a proton to become a conjugate base.

Understanding this pair helps clarify how substances can change roles in chemical reactions, with ammonia transitioning to ammonium once provided with a proton.