Question

Write the formula for the conjugate base of each of the following. (a) \(\mathrm{HSO}_{3}^{-}\) (b) \(\mathrm{H}_{5} \mathrm{IO}_{6}\) (c) \(\mathrm{HNO}_{3}\) (d) \(\mathrm{H}_{2} \mathrm{~S}\)

Short answer

\((a) \mathrm{SO}_{3}^{2-}, (b) \mathrm{H}_{4} \mathrm{IO}_{6}^{-}, (c) \mathrm{NO}_{3}^{-}, (d) \mathrm{HS}^{-}\)

Step-by-step solution

Understanding Conjugate Bases

A conjugate base is formed by the removal of a proton (H+) from an acid. For each given acid, identify the hydrogen atom that will be removed to form the conjugate base.

Conjugate Base of \(\mathrm{HSO}_{3}^{-}\)

Remove a proton (H+) from \(\mathrm{HSO}_{3}^{-}\) to get its conjugate base. The resulting conjugate base is \(\mathrm{SO}_{3}^{2-}\).

Conjugate Base of \(\mathrm{H}_{5} \mathrm{IO}_{6}\)

Remove a proton (H+) from \(\mathrm{H}_{5} \mathrm{IO}_{6}\) to get its conjugate base. The resulting conjugate base is \(\mathrm{H}_{4} \mathrm{IO}_{6}^{-}\).

Conjugate Base of \(\mathrm{HNO}_{3}\)

Remove a proton (H+) from \(\mathrm{HNO}_{3}\) to get its conjugate base. The resulting conjugate base is \(\mathrm{NO}_{3}^{-}\).

Conjugate Base of \(\mathrm{H}_{2} \mathrm{~S}\)

Remove a proton (H+) from \(\mathrm{H}_{2} \mathrm{~S}\) to get its conjugate base. The resulting conjugate base is \(\mathrm{HS}^{-}\).

Key concepts

Acid-Base Chemistry

Acid-base chemistry is a foundational aspect of chemical science dealing with acids and bases. It includes the study of their properties, how they react with each other, and how they can be identified. A crucial concept in this field is the Brønsted-Lowry theory, which defines an acid as a substance that can donate a proton (H+), and a base as a substance that can accept a proton. A conjugate acid-base pair is made up of two species that transform into each other by the gain or loss of a proton. For instance, when a strong acid like hydrochloric acid (HCl) dissolves in water, it donates a proton to a water molecule, creating hydronium (H_3O^+) and chloride ion (Cl^-), its conjugate base. The ability to navigate through these concepts is pivotal for solving exercises related to acid-base reactions, such as finding the conjugate base of a given acid.

Proton Removal

Proton removal, often referred to as deprotonation, is a key step in many acid-base reactions. It involves the detachment of a proton (H+) from an acid, resulting in the formation of its conjugate base. This process is influenced by factors such as the strength of the acid and the particular solvent the reaction takes place in. A strong acid, for example, will easily lose a proton due to its high tendency to donate H+. The conjugate base formed is often more stable than the original acid molecule, due to the dispersion of charge or other factors like resonance stabilization.

In the context of the provided exercise, understanding proton removal is critical. For the compound HSO_3^-, removing one hydrogen atom, specifically the proton, will result in its conjugate base, SO_3^{2-}. The concept of proton removal can sometimes be challenging for students, and a step-by-step approach, like identifying the specific hydrogen atom to be removed, greatly aids in visualizing the resultant chemical species.

Chemical Notation

Chemical notation is the universal language through which chemists communicate the composition and structure of chemical compounds. It uses symbols for elements, numbers to indicate the quantity of atoms, and charges to signify the electronic state of species. In acid-base chemistry, notating conjugate bases correctly is vital to convey the change that occurs when an acid loses a proton. For instance, when we illustrate the chemical reaction where HNO_3 loses a proton, we use chemical notation to show that the remaining particle is NO_3^-, which represents the conjugate base of nitric acid.

As students encounter chemical notation in textbook exercises, it's essential to understand how the notation reflects the molecular structure and charge distribution within the compound. Recognizing that removing a proton decreases the positive charge by one unit can also help with predicting and writing the formulas for conjugate bases effectively. Chemical notation does more than just name the compounds; it allows for the prediction of chemical behavior, interaction, and representation of complex chemical phenomena in a comprehensible manner.