Question

Write the conjugate acid for each of the following bases: a. \(\mathrm{HSO}_{4}^{-}\) b. \(\mathrm{SO}_{3}^{2-}\) c. \(\mathrm{ClO}_{4}^{-}\) d. \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)

Short answer

The conjugate acids for the given bases are: a. \(\mathrm{H}_{2} \mathrm{SO}_{4}\) for \(\mathrm{HSO}_{4}^{-}\) b. \(\mathrm{HSO}_{3}^{-}\) for \(\mathrm{SO}_{3}^{2-}\) c. \(\mathrm{HClO}_{4}\) for \(\mathrm{ClO}_{4}^{-}\) d. \(\mathrm{H}_{3} \mathrm{PO}_{4}\) for \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)

Step-by-step solution

Identify the given bases

We are given the following bases: a. \(\mathrm{HSO}_{4}^{-}\) b. \(\mathrm{SO}_{3}^{2-}\) c. \(\mathrm{ClO}_{4}^{-}\) d. \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)

Add a proton (H+) to each base

Add a proton (H+) to each of the given bases to form their conjugate acids: a. \(\mathrm{HSO}_{4}^{-} + \mathrm{H}^{+} \rightarrow \mathrm{H}_{2} \mathrm{SO}_{4}\) b. \(\mathrm{SO}_{3}^{2-} + \mathrm{H}^{+} \rightarrow \mathrm{HSO}_{3}^{-}\) c. \(\mathrm{ClO}_{4}^{-} + \mathrm{H}^{+} \rightarrow \mathrm{HClO}_{4}\) d. \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-} + \mathrm{H}^{+} \rightarrow \mathrm{H}_{3} \mathrm{PO}_{4}\)

Write the conjugate acids

The conjugate acids for the given bases are: a. \(\mathrm{H}_{2} \mathrm{SO}_{4}\) for \(\mathrm{HSO}_{4}^{-}\) b. \(\mathrm{HSO}_{3}^{-}\) for \(\mathrm{SO}_{3}^{2-}\) c. \(\mathrm{HClO}_{4}\) for \(\mathrm{ClO}_{4}^{-}\) d. \(\mathrm{H}_{3} \mathrm{PO}_{4}\) for \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)

Key concepts

Acid-Base Reactions

Understanding acid-base reactions is foundational in chemistry. These are reactions where an acid donates a proton (a hydrogen ion, \(\mathrm{H}^+\)) to a base, which accepts it. In the context of the given exercise, we looked at how to find the conjugate acid of a base. For example, when the base \(\mathrm{HSO}_{4}^{-}\) accepts a proton, it becomes the conjugate acid \(\mathrm{H}_{2}\mathrm{SO}_{4}\).

It's like a dance between partners: the acid hands off a proton, and the base takes it. In an aqueous solution, this exchange happens quite fluidly. The strength of an acid or base dictates how willing it is to give up or accept a proton. Strong acids, like hydrochloric acid (\(\mathrm{HCl}\)), give their protons away easily, while weak acids, like acetic acid (\(\mathrm{CH}_3\mathrm{COOH}\)), don't give them up as readily.

Relevance to Everyday Life

These reactions aren't just textbook examples; they're happening in your kitchen when you mix vinegar and baking soda, and in your body, where they help maintain a balanced pH in your blood.

Brønsted-Lowry Theory

Brønsted-Lowry theory broadens the concept of acids and bases far beyond the old definitions of just sour or bitter substances. According to this theory, an acid is defined as a substance that can donate a proton (\(\mathrm{H}^+\)), and a base is one that can accept a proton.

This theory also introduces the idea of conjugate acid-base pairs. When an acid donates a proton, it forms its conjugate base, which is what's left after the proton is given away. Conversely, when a base accepts a proton, it forms its conjugate acid. A common example is when ammonia (\(\mathrm{NH}_3\)), a base, accepts a proton and becomes its conjugate acid, ammonium (\(\mathrm{NH}_4^+\)).

Understanding Conjugates

Our exercise tasks students with identifying conjugate acids for bases given. It simplifies the complex dance of protons in a reaction, aiding in grasping the dynamic interplay between molecules during chemical reactions.

Chemical Equilibrium

Chemical equilibrium is a state in a chemical reaction where the rates of the forward reaction (reactants forming products) and reverse reaction (products reverting back to reactants) are equal, resulting in no net change in the concentration of reactants and products over time.

Applying this to acid-base reactions, when an acid donates a proton to a base, reaching equilibrium means the conjugate base (formed from the acid by losing a proton) and the conjugate acid (formed from the base by gaining a proton) exist in certain relative amounts that don't change. It's like a crowded room where an equal number of people are entering and leaving at all times, so the total number of people inside the room remains constant.

Equilibrium and Concentrations

In practice, knowing the principles of chemical equilibrium allows chemists to predict how changing conditions (like concentration, temperature, or pressure) will affect the position of equilibrium and therefore the outcome of a reaction. It's essential for controlling product yield in industrial chemical processes and even in biological systems.