Question

Write the formula for the conjugate acid of each of the following. (a) \(\mathrm{N}_{2} \mathrm{H}_{4}\) (b) \(\mathrm{O}^{2-}\) (c) \(\mathrm{SO}_{4}^{2-}\) (d) \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)

Short answer

The conjugate acids are (a) \(\mathrm{N}_{2} \mathrm{H}_{5}^{+}\), (b) \(\mathrm{OH}^{-}\), (c) \(\mathrm{HSO}_{4}^{-}\), (d) \(\mathrm{H}_{3} \mathrm{PO}_{4}\).

Step-by-step solution

Understanding Conjugate Acids

A conjugate acid is the species formed when a base gains a proton (H+). The formula for the conjugate acid of a base is created by adding one hydrogen ion to the base.

Conjugate Acid of \(\mathrm{N}_{2} \mathrm{H}_{4}\)

To find the conjugate acid of hydrazine \(\mathrm{N}_{2} \mathrm{H}_{4}\), we add a hydrogen ion (H+) to it, resulting in \(\mathrm{N}_{2} \mathrm{H}_{5}^+\).

Conjugate Acid of \(\mathrm{O}^{2-}\)

To find the conjugate acid of the oxide ion \(\mathrm{O}^{2-}\), we add a hydrogen ion (H+) to it, resulting in \(\mathrm{OH}^{-}\).

Conjugate Acid of \(\mathrm{SO}_{4}^{2-}\)

To find the conjugate acid of the sulfate ion \(\mathrm{SO}_{4}^{2-}\), we add a hydrogen ion (H+) to it, resulting in \(\mathrm{HSO}_{4}^{-}\).

Conjugate Acid of \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)

To find the conjugate acid of the dihydrogen phosphate ion \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\), we add a hydrogen ion (H+) to it, resulting in \(\mathrm{H}_{3} \mathrm{PO}_{4}\).

Key concepts

Acid-Base Reactions

Understanding the dynamics of acid-base reactions is crucial for exploring the depths of chemistry. At its heart, an acid-base reaction involves the exchange of a proton (H+) between a pair of substances known as an acid and a base.

When an acid releases a proton, it becomes a base known as the 'conjugate base'. Conversely, when a base receives a proton, it transforms into an 'acid', more specifically called the 'conjugate acid'. This interchangeable play defines the acid-base relationship in chemistry. To visualize these transformative reactions, chemists use equation representations where acids and bases switch roles through the gain or loss of protons, demonstrating the fluidity of their 'conjugate' forms.

Example:

• The reaction between ammonia ( \(NH_3\) ) and water ( \(H_2O\) ) can be represented as: \[NH_3 + H_2O \rightarrow NH_4^+ + OH^-\] Here, ammonia takes a proton from water, forming ammonium ( \(NH_4^+\) ), the conjugate acid, and hydroxide ( \(OH^-\) ), the conjugate base.

These reactions underline the essential concept of reversibility in acid-base chemistry, showcasing that both components—the acid and the base—can flip roles, leading to a better understanding of the equilibrium within chemical reactions.

Proton (H+) Transfer

At the core of acid-base chemistry lies the concept of proton (H+) transfer, a process that's as simple as it sounds yet immensely significant in chemical interactions. A proton is essentially a hydrogen atom that has lost its single electron, leaving behind a positively charged nucleus, which is effectively a hydrogen ion (\(H^+\)).

The transfer of a proton is the fundamental step that determines whether a substance acts as an acid or a base. Acids are proton donors, meaning they can release a proton into their surrounding environment. Bases, on the other hand, are proton acceptors, grabbing available protons to form more stable structures.

Significance of Proton Transfer

In the realm of chemistry, the movement of a single proton can alter the identity and properties of a molecule, as seen in the formation of conjugate acids and bases. This shift in protons can have significant implications, from changing the pH of a solution to affecting reaction mechanisms in both organic and inorganic systems. Proton transfer is so fundamental that it is exploited in various chemical processes, including energy production in biological systems, nutrient absorption, and the buffering capacity of blood.

Chemical Formulas of Acids

Diving into the intricate world of chemistry means becoming familiar with the chemical formulas of acids. Acids, known as proton donors, are generally represented by their unique formulas that often include hydrogen (\(H\)) at the front. These hydrogen ions are the ones that are released during acid-base reactions.

Common acids have recognizable formulas that are cornerstones of chemistry education:

• Hydrochloric acid ( \(HCl\) )
• Sulfuric acid ( \(H_2SO_4\) )
• Acetic acid ( \(CH_3COOH\) )

Understanding these formulas is not just a matter of memorization but grasping how the presence of hydrogen ions (\(H^+\)) links to the acids’ properties and behaviors. For instance, in the chemical reactions presented in the exercise, adding a hydrogen ion alters a molecule's formula, thereby converting neutral or negatively charged species into their respective conjugate acids. This change gives rise to new substances with potentially different reactivity and characteristics, an aspect that is key to predicting outcomes in chemical equations and laboratory experiments.