Question

Write the conjugate acid for each of the following bases: a. \(\mathrm{PO}_{4}^{3-}\) b. \(\mathrm{IO}_{3}^{-}\) c. \(\mathrm{NO}_{3}^{-}\) d. \(\mathrm{NH}_{2}^{-}\)

Short answer

The conjugate acids for the given bases are: a. \(\mathrm{HPO}_{4}^{2-}\) b. \(\mathrm{HIO}_{3}\) c. \(\mathrm{HNO}_{3}\) d. \(\mathrm{NH}_{3}\)

Step-by-step solution

Add a proton to the given base

To find the conjugate acid, we will add a proton (H+) to the given base. As a result, the total charge of the molecule will also decrease by one.

Determine the conjugate acid for \(\mathrm{PO}_{4}^{3-}\)

To form the conjugate acid of \(\mathrm{PO}_{4}^{3-}\), we add H+ to it: \[ \mathrm{HPO}_{4}^{2-} \] The conjugate acid is \(\mathrm{HPO}_{4}^{2-}\).

Determine the conjugate acid for \(\mathrm{IO}_{3}^{-}\)

To form the conjugate acid of \(\mathrm{IO}_{3}^{-}\), we add H+ to it: \[ \mathrm{HIO}_{3}^{0} \] The conjugate acid is \(\mathrm{HIO}_{3}\).

Determine the conjugate acid for \(\mathrm{NO}_{3}^{-}\)

To form the conjugate acid of \(\mathrm{NO}_{3}^{-}\), we add H+ to it: \[ \mathrm{HNO}_{3}^{0} \] The conjugate acid is \(\mathrm{HNO}_{3}\).

Determine the conjugate acid for \(\mathrm{NH}_{2}^{-}\)

To form the conjugate acid of \(\mathrm{NH}_{2}^{-}\), we add H+ to it: \[ \mathrm{NH}_{3}^{0} \] The conjugate acid is \(\mathrm{NH}_{3}\).

Key concepts

Base Chemistry

In base chemistry, a base is generally defined as a substance that can accept a proton or donate a pair of valence electrons to form a bond. Bases are an essential part of the chemistry involving acids because bases often interact with acids in what are known as acid-base reactions. Bases can be ionic compounds, such as hydroxide ions (OH\(^{-}\)), or covalent compounds containing nitrogen, like ammonia (NH\(_{3}\)).
Understanding the behavior of different bases helps elucidate how they interact with acids to produce conjugate acids and bases. When a base gains a proton (H\(^+\)), it forms its conjugate acid. Each base has a distinct conjugate acid depending on its structure and charge. The knowledge of such transformations is vital in predicting chemical reaction outcomes in broader chemical reactions.

Proton Addition

Proton addition is a fundamental concept when studying acid-base chemistry. It is the process by which a proton (H\(^+\)) is added to a molecule or ion. This process is characterized by an increase in proton number, which typically changes the properties of the original substance.
Here's how proton addition works for conjugate acid formation:

• For a base such as phosphate (\(\mathrm{PO}_{4}^{3-}\)), adding a proton results in \(\mathrm{HPO}_{4}^{2-}\). This addition of \(\mathrm{H}^+\) neutralizes one negative charge.
• Similarly, when using iodate (\(\mathrm{IO}_{3}^{-}\)) as the base, proton addition forms \(\mathrm{HIO}_{3}\). The added proton removes the ion's negative charge.
• This rule applies to nitrate (\(\mathrm{NO}_{3}^{-}\)) and amide (\(\mathrm{NH}_{2}^{-}\)), forming \(\mathrm{HNO}_{3}\) and \(\mathrm{NH}_{3}\), respectively.

This method is a straightforward way to determine the conjugate acid from a base, as it involves only the straightforward addition of a single proton.

Acid-Base Reactions

Acid-base reactions are at the heart of many chemical processes, involving the transfer of protons between reactants. These reactions are crucial for various biological functions and industrial applications. In these reactions, an acid (a proton donor) transfers a proton to a base (a proton acceptor) forming their respective conjugate base and conjugate acid.
Here's a simplified look at what happens in these reactions:

• The acid loses a proton and becomes a conjugate base. For example, when \(\mathrm{HCl}\) donates a proton, it forms \(\mathrm{Cl}^-\) as its conjugate base.
• Conversely, the base accepts a proton, forming a conjugate acid. In the textbook example, bases like \(\mathrm{PO}_{4}^{3-}\) and \(\mathrm{NH}_{2}^{-}\) change into their respective conjugate acids: \(\mathrm{HPO}_{4}^{2-}\) and \(\mathrm{NH}_{3}\), upon accepting a proton.

Understanding these interactions provides valuable insight into the behavior of acids and bases in both laboratory and real-world settings, revealing the subtleties of equilibrium and reactivity in chemical systems.