Problem 18 - Chemistry: An Atoms-Focused Approach

Question

Identify the conjugate acid of each of the following species: \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}, \mathrm{CH}_{3} \mathrm{COO}^{-}, \mathrm{HSO}_{4}^{-},\) and \(\mathrm{OH}^{-}\)

Step-by-Step Solution

Answer

Answer: The conjugate acids of the given species are: 1. \((\mathrm{CH}_{3})_{3} \mathrm{N}\): \((\mathrm{CH}_{3})_{3}\mathrm{NH}^{+}\) 2. \(\mathrm{CH}_{3}\mathrm{COO}^{-}\): \(\mathrm{CH}_3\mathrm{COOH}\) 3. \(\mathrm{HSO}_{4}^{-}\): \(\mathrm{H}_{2}\mathrm{SO}_{4}\) 4. \(\mathrm{OH}^{-}\): \(\mathrm{H}_{2}\mathrm{O}\)

Step 1: Add a hydrogen ion to \((\mathrm{CH}_{3})_{3} \mathrm{N}\)

To find the conjugate acid of \((\mathrm{CH}_{3})_{3} \mathrm{N}\), we need to add one hydrogen ion to the molecule: \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N} + \mathrm{H}^{+} = \left(\mathrm{CH}_{3}\right)_{3}\mathrm{NH}^{+}\)

Step 2: Add a hydrogen ion to \(\mathrm{CH}_{3}\mathrm{COO}^{-}\)

To find the conjugate acid of \(\mathrm{CH}_{3}\mathrm{COO}^{-}\), we need to add one hydrogen ion to the ion: \(\mathrm{CH}_{3}\mathrm{COO}^{-} + \mathrm{H}^{+} = \mathrm{CH}_{3}\mathrm{COOH}\)

Step 3: Add a hydrogen ion to \(\mathrm{HSO}_{4}^{-}\)

To find the conjugate acid of \(\mathrm{HSO}_{4}^{-}\), we need to add one hydrogen ion to the ion: \(\mathrm{HSO}_{4}^{-} + \mathrm{H}^{+} = \mathrm{H}_{2}\mathrm{SO}_{4}\)

Step 4: Add a hydrogen ion to \(\mathrm{OH}^{-}\)

To find the conjugate acid of \(\mathrm{OH}^{-}\), we need to add one hydrogen ion to the ion: \(\mathrm{OH}^{-} + \mathrm{H}^{+} = \mathrm{H}_{2}\mathrm{O}\)

Step 5: Summarizing Conjugate Acids

The conjugate acids of the given species are: 1. \((\mathrm{CH}_{3})_{3} \mathrm{N}\): \((\mathrm{CH}_{3})_{3}\mathrm{NH}^{+}\) 2. \(\mathrm{CH}_{3}\mathrm{COO}^{-}\): \(\mathrm{CH}_3\mathrm{COOH}\) 3. \(\mathrm{HSO}_{4}^{-}\): \(\mathrm{H}_{2}\mathrm{SO}_{4}\) 4. \(\mathrm{OH}^{-}\): \(\mathrm{H}_{2}\mathrm{O}\)

Key Concepts

Understanding Acid-Base Chemistry

Acid-base chemistry is a fundamental concept in chemistry that revolves around the exchange of protons, or hydrogen ions (\( \mathrm{H}^{+} \)), between different chemical species.
Understanding acid-base reactions can help us predict the behavior of substances in various environments, ranging from industrial processes to biological systems.
In the realm of acid-base chemistry, acids are species that donate protons, while bases are those that accept protons. The process of donating and accepting protons leads to the formation of conjugate acids and bases.
When an acid donates a proton, the remaining part of the acid is called its conjugate base.
Similarly, when a base accepts a proton, it forms its conjugate acid.
To visualize this, let's take the example of water (\( \mathrm{H}_2\mathrm{O} \)).
When water acts as an acid and donates a proton, it forms hydroxide ions (\( \mathrm{OH}^{-} \)), which act as its conjugate base.
When water acts as a base and accepts a proton, it forms hydronium ions (\( \mathrm{H}_3\mathrm{O}^{+} \)), its conjugate acid.
This concept of conjugate acids and bases is central to understanding many chemical reactions and is essential for solving problems related to acid-base chemistry.

The Role of Chemical Species

In acid-base reactions, the term 'chemical species' refers to ions or molecules that participate in the reaction as either acids or bases.

These entities can vary in size, charge, and complexity.
In the exercise referenced, the species under consideration include \( (\mathrm{CH}_3)_3\mathrm{N} \), \( \mathrm{CH}_3\mathrm{COO}^- \), \( \mathrm{HSO}_4^- \), and \( \mathrm{OH}^- \). Understanding the roles these species play in chemical reactions is vital.
This is because the properties of chemical species determine their reactivity and ability to donate or accept protons.
Each species will either yield or gain a proton to form its corresponding conjugate acid or base.
For example, when \( \mathrm{OH}^{-} \) accepts a proton, it becomes \( \mathrm{H}_{2}\mathrm{O} \), showing the transformation from a base to its conjugate acid. This transformation is how a chemical species is involved in proton transfer, dictating the overall dynamics of the reaction.
Mastering the concept of chemical species in proton exchange helps us predict and rationalize the outcomes of acid-base reactions.

Proton Transfer and Its Significance

Proton transfer is the heart of acid-base reactions and is what allows these reactions to take place.

When we talk about proton transfer, we mean the movement of the \( \mathrm{H}^{+} \) ion from one chemical species to another. This transfer is vital because it is responsible for the conversion of acids to bases and vice versa through the formation of conjugate pairs.
An acid will transfer a proton to a base, forming its conjugate base and the base's conjugate acid in the process.For instance, in the exercise, \( \mathrm{CH}_3\mathrm{COO}^{-} \) receives a proton to become \( \mathrm{CH}_3\mathrm{COOH} \), its conjugate acid.
This illustrates the flow of a proton from one entity, demonstrating its ability to change the chemical nature of participating species.Proton transfer can affect properties such as pH, reactivity, and solubility of the reacting species.
It is the underpinning concept that helps chemists to manipulate chemical reactions and understand processes occurring in diverse fields like environmental chemistry and pharmaceuticals.
Grasping the details of proton transfer equips you with the knowledge to solve complex problems related to acid-base equilibria.