Question

Name each of the following acids. a. \(HOCl\) b. \(\mathrm{H}_{2} \mathrm{SO}_{3}\) c. \(\mathrm{HBrO}_{3}\) d. \(HOI\) e. \(\mathrm{HBrO}_{4}\) f. \(\mathrm{H}_{2} \mathrm{S}\) \(\mathrm{g} \cdot \mathrm{H}_{2} \mathrm{Se}\) \(\overline{\mathrm{h}} . \mathrm{H}_{3} \mathrm{PO}_{3}\)

Short answer

a. Hypochlorous acid b. Sulfurous acid c. Bromic acid d. Iodous acid e. Perbromic acid f. Hydrosulfuric acid g. Hydroselenic acid h. Phosphorous acid

Step-by-step solution

a. Naming \(HOCl\)

This is a ternary acid with the oxyanion \(ClO^-\). The anion name is hypochlorite, so the acid name is hypochlorous acid.

b. Naming \(\mathrm{H}_{2} \mathrm{SO}_{3}\)

This is a ternary acid with the oxyanion \(SO_3^{2-}\). The anion name is sulfite, so the acid name is sulfurous acid.

c. Naming \(\mathrm{HBrO}_{3}\)

This is a ternary acid with the oxyanion \(BrO_3^-\). The anion name is bromate, so the acid name is bromic acid.

d. Naming \(HOI\)

This is a ternary acid with the oxyanion \(IO^-\). The anion name is iodite, so the acid name is iodous acid.

e. Naming \(\mathrm{HBrO}_{4}\)

This is a ternary acid with the oxyanion \(BrO_4^-\). The anion name is perbromate, so the acid name is perbromic acid.

f. Naming \(\mathrm{H}_{2} \mathrm{S}\)

This is a binary acid with the anion \(S^{2-}\). The anion name is sulfide, so the acid name is hydrosulfuric acid.

g. Naming \(\mathrm{H}_{2} \mathrm{Se}\)

This is a binary acid with the anion \(Se^{2-}\). The anion name is selenide, so the acid name is hydroselenic acid.

h. Naming \(\mathrm{H}_{3} \mathrm{PO}_{3}\)

This is a ternary acid with the oxyanion \(PO_3^{3-}\). The anion name is phosphite, so the acid name is phosphorous acid.

Key concepts

Ternary Acids

Ternary acids, also known as oxyacids, contain hydrogen, oxygen, and another non-metal element. These acids derive their names from the polyatomic ions (or oxyanions) they contain. For example, in the case of (HOCl), the oxyanion is hypochlorite. To name ternary acids, you typically replace the -ite or -ate suffix of the oxyanion with -ous or -ic, respectively.

• -ite becomes -ous: If the oxyanion ends in '-ite', the acid name will end in '-ous'.
• -ate becomes -ic: If the oxyanion ends in '-ate', the acid name will end in '-ic'.

Some common examples include: - Sulfite ( (SO_3^{2-})) becoming sulfurous acid ( (H_2SO_3)). - Phosphite ( (PO_3^{3-})) becoming phosphorous acid ( (H_3PO_3)). Understanding how ternary acids are formed from their corresponding oxyanions is crucial for learning chemical nomenclature.

Binary Acids

Binary acids consist of just two elements: hydrogen and one other non-metal. These acids are typically named starting with the prefix 'hydro-', followed by the root of the non-metal’s name, and ending with the suffix '-ic'. For example, (H_2S) has the anion sulfide ( (S^{2-})), and thus it is named hydrosulfuric acid.

• Hydrosulfuric acid is formed from hydrogen and sulfur.
• Hydroselenic acid stems from hydrogen and selenium, as in the compound (H_2Se).

Recognizing binary acids is simpler than ternary acids because their structure and naming convention are straightforward. Understanding this category helps in easily distinguishing acids based on their composition.

Oxyanions

Oxyanions are negatively charged ions consisting of oxygen bonded to another element, typically a non-metal. These ions form the basis of various ternary acids. Oxyanions often exist in series, where the element can have multiple oxidation states. For example, chlorine can form different oxyanions such as (ClO^-), (ClO_2^-), (ClO_3^-), and (ClO_4^-):

• -ite: Fewer oxygen molecules (e.g., (ClO_2^-) is chlorite).
• -ate: More oxygen molecules (e.g., (ClO_3^-) is chlorate).
• Prefixes such as "hypo-" and "per-" can indicate the least or most oxygen:
• Hypochlorite ( (ClO^-)) indicates one less oxygen than chlorite.
• Perchlorate ( (ClO_4^-)) indicates one more oxygen than chlorate.

Understanding oxyanions also facilitates the learning of corresponding ternary acid names by recognizing the relevant oxyanion structure.

Acid Naming Rules

Naming acids properly is crucial for understanding chemical formulas and reactions. Different rules apply based on whether the acid is binary or ternary:

• Binary acids: Named with 'hydro-' prefix and '-ic' suffix (e.g., hydrochloric acid for (HCl)).
• Ternary acids: Named based on the oxyanion: '-ite' anions become '-ous acids', and '-ate' anions become '-ic acids' (e.g., sulfurous acid from sulfite).

It’s also important to note certain systematic prefixes and suffixes: - 'per-' and 'hypo-' are used to indicate variations in oxygen content among oxyanions. - '-ic' typically indicates a higher oxidation state of the central element compared to '-ous'. Consistently applying these rules helps in accurately naming and identifying acids in their scientific context. This clarity assists students in both laboratory settings and theoretical studies, where precise chemical language is required.