Question

Give the name or chemical formula, as appropriate, for each of the following acids: (a) \(\mathrm{HBrO}_{3}\), (b) \(\mathrm{HBr}\), (c) \(\mathrm{H}_{3} \mathrm{PO}_{4},(\mathrm{~d})\) hypochlorous acid, \((\mathrm{e})\) iodic acid, \((\mathrm{f})\) sulfurous acid.

Short answer

(a) The name of \(\mathrm{HBrO}_3\) is bromic acid. (b) The name of \(\mathrm{HBr}\) is hydrobromic acid. (c) The name of \(\mathrm{H}_{3} \mathrm{PO}_{4}\) is phosphoric acid. (d) The chemical formula for hypochlorous acid is \(\mathrm{HClO}\). (e) The chemical formula for iodic acid is \(\mathrm{HIO}_3\). (f) The chemical formula for sulfurous acid is \(\mathrm{H}_{2}\mathrm{SO}_{3}\).

Step-by-step solution

(a) Finding the name for \(\mathrm{HBrO}_{3}\)

We first check the anion part, which is \(\mathrm{BrO}_{3}^{-}\). This anion is composed of bromine and oxygen, and it is called bromate anion. When we name the acid, we remove the "-ate" ending from the anion and replace it with the ending "-ic acid". So, the name of the acid is bromic acid.

(b) Finding the name for \(\mathrm{HBr}\)

The anion in this acid is \(\mathrm{Br}^{-}\), which is called bromide. With this type of anion, we use the stem of the element name and add the suffix "-hydro-...-ic acid". In this case, the name of the acid is hydrobromic acid.

(c) Finding the name for \(\mathrm{H}_{3} \mathrm{PO}_{4}\)

Here, the anion is \(\mathrm{PO}_{4}^{3-}\), which is called phosphate. As in case (a), we remove the "-ate" ending from the anion and replace it with the ending "-ic acid". Therefore, the name of the acid is phosphoric acid.

(d) Finding the chemical formula for hypochlorous acid

Hypochlorous acid is an example of an acid with a "-ous" suffix. We will use the general rule for these acids: drop the "-ous" part of the word and replace it with the ending "-ite" for the anion. The resulting anion is hypochlorite. The chemical formula of hypochlorite is \(\mathrm{ClO}^{-}\). So, the chemical formula for hypochlorous acid is \(\mathrm{HClO}\).

(e) Finding the chemical formula for iodic acid

Iodic acid is an example of an acid with an "-ic" suffix. We will use the general rule for these acids: drop the "-ic" part of the word and replace it with the ending "-ate" for the anion. The resulting anion is iodate. The chemical formula for iodate is \(\mathrm{IO}_{3}^{-}\). So, the chemical formula for iodic acid is \(\mathrm{HIO}_3\).

(f) Finding the chemical formula for sulfurous acid

Sulfurous acid is another example of an acid with a "-ous" suffix. As in case (d), we will drop the "-ous" part of the word and replace it with the ending "-ite" for the anion. The resulting anion is called sulfite, and its chemical formula is \(\mathrm{SO}_{3}^{2-}\). Sulfurous acid contains two hydrogen atoms because the charge of sulfite is \(2-\). So, the chemical formula for the sulfurous acid is \(\mathrm{H}_{2}\mathrm{SO}_{3}\).

Key concepts

Chemical Formula of Acids

Understanding the chemical formula of acids begins with recognizing that acids are substances that release hydrogen ions (H+) when dissolved in water. The formula of an acid reflects its ability to donate these hydrogen ions.

For instance, in the molecule (HBrO_3), the acid is composed of hydrogen (H) bonded to a polyatomic ion (BrO_3^-), creating bromic acid. Each acid's formula gives us crucial information about its properties and behavior during chemical reactions.

To form a clear understanding of any acid, it's essential to recognize the hydrogen component coupled with its associated anion, as it is the interplay between these two parts that defines the acid's characteristics.

Acid Nomenclature Rules

The rules for naming acids hinge on their anionic counterparts. If the anion name ends in '-ate', the acid's name will end in '-ic'. (HBrO_3) therefore becomes bromic acid, as we replace the 'ate' from bromate (BrO_3^-) with 'ic'.

For anions with names ending in '-ite', the acid's name ends in '-ous', like 'SO_3^{2-}' which is sulfite, leading to the name sulfurous acid. When dealing with simple binary acids—those with hydrogen and one other element—the prefix 'hydro-' is added to the root of the nonmetal's name, and the suffix '-ic acid' is used. This is why HBr, composed of hydrogen and bromine, is named hydrobromic acid.

Polyatomic Ions in Acids

The presence of polyatomic ions in acids significantly influences the properties and names of the acids. These are ions composed of more than one atom, like phosphate (PO_4^{3-}) or sulfite (SO_3^{2-}).

Acids that contain polyatomic ions often have names derived from these ions. When the ion's name ends in '-ate', the acid name changes to '-ic acid', and if the ion's name ends in '-ite', the acid's name becomes '-ous acid'. Recognizing and understanding polyatomic ions is vital, as they form the structural foundation that defines how the acid behaves chemically and how it is named.

Acid-Base Chemistry

Acid-base chemistry is a fundamental concept that deals with the reactions between acids and bases. It largely revolves around the transfer of protons (H+) from acids to bases. Acids are proton donors, while bases are proton acceptors.

This transfer leads to the formation of water when a strong acid reacts with a strong base, a process known as neutralization. Understanding how acids release protons, and the role of the conjugate base—the species that remains after the acid donates its proton—is essential to grasp the broader implications of acid-base reactions. These principles underscore the dynamic nature of acids, highlighting their ability to engage in chemical processes that are fundamental to fields ranging from industrial chemistry to biological systems.