Problem 18 - Chemistry The Science in Context

Question

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

Step-by-Step Solution

Answer

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

Step 1: Add a proton to \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}\)

To form the conjugate acid of \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}\), we need to add a proton (H+) to it, which results in the following chemical formula: \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{NH}^{+}\).

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

To form the conjugate acid of \(\mathrm{CH}_{3} \mathrm{COO}^{-}\), we need to add a proton (H+) to it, which results in the following chemical formula: \(\mathrm{CH}_{3} \mathrm{COOH}\).

Step 3: Add a proton to \(\mathrm{OH}^{-}\)

To form the conjugate acid of \(\mathrm{OH}^{-}\), we need to add a proton (H+) to it, which results in the following chemical formula: \(\mathrm{H}_{2}\mathrm{O}\). After following these steps, we have identified the conjugate acid for each of the given species: 1. The conjugate acid of \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{N}\) is \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{NH}^{+}\). 2. The conjugate acid of \(\mathrm{CH}_{3} \mathrm{COO}^{-}\) is \(\mathrm{CH}_{3} \mathrm{COOH}\). 3. The conjugate acid of \(\mathrm{OH}^{-}\) is \(\mathrm{H}_{2}\mathrm{O}\).

Key Concepts

Acid-Base Chemistry

Acid-base chemistry is a fundamental concept in chemistry that deals with how acids and bases interact. Understanding it can help explain many chemical reactions and processes. An "acid" is a substance that can donate a proton, while a "base" is a substance that can accept a proton. This is known as the Brønsted-Lowry definition of acids and bases.
When an acid donates a proton, it forms its conjugate base. Conversely, when a base accepts a proton, it forms its conjugate acid. This process forms the basis of acid-base equilibria and is essential in biological systems, environmental science, and engineering applications.

• Acids donate protons.
• Bases accept protons.
• Conjugate acids and conjugate bases are formed through the donation and acceptance of protons, respectively.

Through these interactions, acids and bases can neutralize each other, leading to products that might be more stable or have different properties. Recognizing the behavior of acids, bases, and their conjugates helps predict the outcomes of many chemical reactions.

Chemical Formulas

Chemical formulas are symbolic representations of chemical compounds. They provide crucial information about the composition of molecules and ions, representing the elements present and their ratios. Each element is represented by its chemical symbol, like C for carbon, H for hydrogen, and O for oxygen.
Subscripts indicate the number of each type of atom in the molecule. For ions, the charge is shown following the chemical formula, such as in the hydroxide ion, OH^-.
In this exercise, the chemical formulas illustrate the compounds and ions before and after protonation, showing how they transform:

• ( CH₃ )₃ N becomes ( CH₃ )₃ NH⁺ after adding a proton.
• CH₃COO^- becomes CH₃COOH.
• OH^- becomes H₂O.

Understanding chemical formulas helps in visualizing chemical changes, like proton transfer, and aids in predicting the outcome of chemical reactions.

Proton Transfer

Proton transfer is a critical process in many chemical reactions, notably in acid-base chemistry. It involves the movement of a proton (H⁺) from one molecule, the acid, to another molecule, the base.
This transfer not only transforms an acid into its conjugate base and a base into its conjugate acid, but it also influences the reaction's equilibrium and the properties of entities involved.

• Protons are hydrogen ions without their electron, depicted as H⁺.
• The addition of a proton to a base forms its conjugate acid, highlighting the reversible nature of acid-base reactions.
• Recognizing proton transfer events is essential for solving problems involving equilibrium, acidity, and reactivity.

This straightforward exchange is at the heart of many processes that control both natural phenomena and industrial processes. Being familiar with proton transfer helps us appreciate how substances can change form and function.