Problem 13 - Chemistry The Molecular Science

Question

Write the formula and name for the conjugate partner for each acid or base. (a) HI (b) \(\mathrm{NO}_{3}^{-}\) (c) \(\mathrm{CO}_{3}^{2-}\) (d) \(\mathrm{H}_{2} \mathrm{CO}_{3}\) (e) \(\mathrm{HSO}_{4}^{-}\) (f) \(\mathrm{SO}_{3}^{2-}\)

Step-by-Step Solution

Answer

(a) \( \mathrm{I}^{-} \), (b) \( \mathrm{HNO}_{3} \), (c) \( \mathrm{HCO}_{3}^{-} \), (d) \( \mathrm{HCO}_{3}^{-} \), (e) \( \mathrm{SO}_{4}^{2-} \) / \( \mathrm{H}_{2} \mathrm{SO}_{4} \), (f) \( \mathrm{HSO}_{3}^{-} \).

Step 1: Understanding Conjugate Acid-Base Pairs

Conjugate acid-base pairs differ by one proton ( +). When an acid donates a proton, it turns into its conjugate base. Conversely, when a base accepts a proton, it turns into its conjugate acid.

Step 2: Determine Conjugate Partner for HI

HI is an acid. When HI donates a proton ( +), it becomes its conjugate base, which is the iodide ion, ^{-}.

Step 3: Determine Conjugate Partner for \( \mathrm{NO}_{3}^{-} \)

\( \mathrm{NO}_{3}^{-} \) is typically a base. If it acts as a base and accepts a proton, it becomes its conjugate acid, which is nitric acid, \( \mathrm{HNO}_{3} \).

Step 4: Determine Conjugate Partner for \( \mathrm{CO}_{3}^{2-} \)

\( \mathrm{CO}_{3}^{2-} \) is a base. When it accepts a proton, it becomes its conjugate acid, \( \mathrm{HCO}_{3}^{-} \) (bicarbonate ion).

Step 5: Determine Conjugate Partner for \( \mathrm{H}_{2} \mathrm{CO}_{3} \)

\( \mathrm{H}_{2} \mathrm{CO}_{3} \) is an acid. When it donates a proton, it turns into its conjugate base, \( \mathrm{HCO}_{3}^{-} \) (bicarbonate ion).

Step 6: Determine Conjugate Partner for \( \mathrm{HSO}_{4}^{-} \)

\( \mathrm{HSO}_{4}^{-} \) can act as both an acid and a base (amphiprotic). As an acid, when it donates a proton, it becomes \( \mathrm{SO}_{4}^{2-} \) (sulfate ion). As a base, when it accepts a proton, it becomes \( \mathrm{H}_{2} \mathrm{SO}_{4} \) (sulfuric acid).

Step 7: Determine Conjugate Partner for \( \mathrm{SO}_{3}^{2-} \)

\( \mathrm{SO}_{3}^{2-} \) is a base. When it accepts a proton, it becomes its conjugate acid, \( \mathrm{HSO}_{3}^{-} \) (bisulfite ion).

Key Concepts

Acid-Base Chemistry

Acid-base chemistry is a fundamental concept in chemistry that revolves around how acids and bases interact. Acids are substances that can donate a proton (which is essentially a hydrogen ion, H+) to another substance. Bases, on the other hand, are substances that can accept these protons. When an acid donates a proton, what's left is called its conjugate base. Conversely, when a base accepts a proton, the result is its conjugate acid. This concept is essential because it explains how substances can change and react under different conditions. Understanding acid-base chemistry helps in predicting the behavior of substances in solutions and is essential for tasks like balancing chemical equations or understanding chemical equilibria. For instance, in an acid-base reaction, the strength of the products' conjugate acids and bases will help determine the direction and extent of the reaction.

Proton Transfer

Proton transfer is the process where a proton, a positively charged hydrogen ion, moves from one molecule to another. This transfer is the essence of acid-base reactions. In a proton transfer reaction:

• The acid is the proton donor.
• The base is the proton acceptor.

This transfer plays a crucial role in biochemical processes, industrial chemistry, and more. For example, this principle is key in the functioning of buffers, which maintain a stable pH in our blood. The strength of the acid and base, as well as the stability of the resulting ions, influences how readily proton transfer occurs. A strong acid will donate a proton more easily, while a strong base will accept one more readily.

Amphiprotic Substances

Some substances have the unique ability to act as both acids and bases. These are known as amphiprotic substances. They can either donate a proton, acting as an acid, or accept a proton, acting as a base. A classic example is the hydrogen sulfate ion (HSO₄⁻). It can donate a proton to form sulfate ion (SO₄²⁻), or accept a proton to form sulfuric acid (H₂SO₄). Amphiprotic substances play a distinct role in chemistry because:

• They help balance reactions by flexibly reacting depending on the surrounding conditions.
• They can participate in both acidic and basic reactions, making them versatile in their chemical behavior.

Understanding amphiprotic behavior is important in fields such as environmental science and human physiology, where such substances may be involved in buffering systems that maintain pH balance.