Question

Give the IUPAC systematic name for each of the following ternary oxyacids: (a) \(\mathrm{HClO}_{4}(a q)\) (b) \(\mathrm{H}_{2} \mathrm{SO}_{3}(a q)\)

Short answer

(a) Perchloric acid (b) Sulfurous acid

Step-by-step solution

Identify the Oxyacid's Anion

The suffix of the IUPAC name for a ternary oxyacid is determined by its anion. Identify the anion in each compound. For \(\mathrm{HClO}_{4}\), the anion is \(\mathrm{ClO}_{4}^{-}\) (perchlorate). For \(\mathrm{H}_{2}\mathrm{SO}_{3}\), the anion is \(\mathrm{SO}_{3}^{2-}\) (sulfite).

Apply Naming Rules for Oxyacids

For oxyacids, if the anion name ends in '-ate', the acid name ends in '-ic acid'. If the anion name ends in '-ite', the acid name ends in '-ous acid'. 'Per' or 'hypo' prefixes are retained for acids containing 'per-' or 'hypo-' anions.

Name the Perchloric Acid

Using the rule, since \(\mathrm{ClO}_{4}^{-}\) is perchlorate which ends with '-ate', the corresponding acid is named as 'perchloric acid'.

Name the Sulfurous Acid

For \(\mathrm{H}_{2}\mathrm{SO}_{3}\), the anion \(\mathrm{SO}_{3}^{2-}\) is sulfite, and because it ends with '-ite', the corresponding acid is named 'sulfurous acid'.

Key concepts

ternary oxyacids

Ternary oxyacids are a class of acids that contain hydrogen, oxygen, and another element. These acids are key in many chemical processes and serve important roles in both biological and industrial contexts. One defining feature of ternary oxyacids is their ability to dissociate in water, releasing hydrogen ions (H⁺) and forming anions. This ability to produce H⁺ ions in solution is what makes them acids by definition.

Often, the third element in a ternary oxyacid is a nonmetal, though this is not a strict rule. These acids are named according to the anion formed when they dissociate in water, which we'll explore further in dedicated sections below. Recognizing the anion is crucial, as it directly influences the IUPAC nomenclature of the compound. Thus, the name of the oxyacid always gives a hint on the nature of the anion present in the acid.

anion identification

Identifying the anion in a ternary oxyacid is a fundamental task when trying to name these compounds properly. An anion is an ion that carries a negative charge, formed from the non-hydrogen components of the original compound after losing positively charged hydrogen ions in solution.

• For example, in the compound \( \mathrm{HClO}_{4} \), the anion is \( \mathrm{ClO}_{4}^{-} \), known as "perchlorate".
• Similarly, in \( \mathrm{H}_{2}\mathrm{SO}_{3} \), the anion \( \mathrm{SO}_{3}^{2-} \) is identified as "sulfite".

Recognizing the anion informs the suffix of the acid's name, as each different anion implies a different kind of acid. This section transitions from the understanding of anions into how they aid in constructing chemical names per IUPAC guidelines.

chemical naming rules

The naming of ternary oxyacids follows certain conventions set by IUPAC (International Union of Pure and Applied Chemistry), which ensure consistency and clarity in the way chemical compounds are named globally. For oxyacids, these rules revolve mostly around the names of the anions involved.

**Key Naming Rules:**

• If an anion name ends in "-ate," the corresponding acid name ends in "-ic acid."
• If an anion ends in "-ite," the acid name ends in "-ous acid."
• Prefixes like "per-" and "hypo-" are kept intact when referring to the related acids.

For example, perchlorate anion \( \mathrm{ClO}_{4}^{-} \) leads to the acid being named "perchloric acid," while the sulfite anion \( \mathrm{SO}_{3}^{2-} \) is named "sulfurous acid" in the acid form. These rules help streamline communication in chemistry by providing a systematic method for naming acids based on their chemical composition.