Question

Write the formula for each of the following acids. a. hydrosulfuric acid b. perbromic acid c. acetic acid d. hydrobromic acid e. chlorous acid f. hydroselenic acid g. sulfurous acid h. perchloric acid

Short answer

The formula for each of the given acids is as follows: a. Hydrosulfuric acid: \(H_2S\) b. Perbromic acid: \(HBrO_4\) c. Acetic acid: \(CH_3COOH\) d. Hydrobromic acid: \(HBr\) e. Chlorous acid: \(HClO_2\) f. Hydroselenic acid: \(H_2Se\) g. Sulfurous acid: \(H_2SO_3\) h. Perchloric acid: \(HClO_4\)

Step-by-step solution

a. Hydrosulfuric acid

The anion of hydrosulfuric acid ends in -ide, so we add "hydro-" to the beginning and change the ending to "-ic acid". The anion is sulfide (S^2-). The acid formula is H2S.

b. Perbromic acid

The anion of perbromic acid ends in -ate, so we leave the root element and change the ending to "-ic acid". The anion is perbromate (BrO4^-). The acid formula is HBrO4.

c. Acetic acid

Acetic acid is an organic acid with the name ending in "-ic acid". It has the formula CH3COOH.

d. Hydrobromic acid

The anion of hydrobromic acid ends in -ide, so we add "hydro-" to the beginning and change the ending to "-ic acid". The anion is bromide (Br^-). The acid formula is HBr.

e. Chlorous acid

The anion of chlorous acid ends in -ite, so we leave the root element and change the ending to "-ous acid". The anion is chlorite (ClO2^-). The acid formula is HClO2.

f. Hydroselenic acid

The anion of hydroselenic acid ends in -ide, so we add "hydro-" to the beginning and change the ending to "-ic acid". The anion is selenide (Se^2-). The acid formula is H2Se.

g. Sulfurous acid

The anion of sulfurous acid ends in -ite, so we leave the root element and change the ending to "-ous acid". The anion is sulfite (SO3^2-). The acid formula is H2SO3.

h. Perchloric acid

The anion of perchloric acid ends in -ate, so we leave the root element and change the ending to "-ic acid". The anion is perchlorate (ClO4^-). The acid formula is HClO4.

Key concepts

Acid Formula

Understanding the acid formula is an essential part of chemistry that deals with how to represent acids in chemical notation. An acid is a substance that can donate protons (H⁺) and usually has a sour taste. The formula for an acid typically starts with the hydrogen ion (H⁺) followed by its anion.

For example, hydrosulfuric acid, which has the anion sulfide (S^2-), is represented by the formula H₂S. Notice how the hydrogen is listed first, indicating its role as the acidic proton donor. It's important to recognize the two types of acids: those with an anion ending in '-ide' get the prefix 'hydro-', plus '-ic acid'. So, the name 'hydrosulfuric acid' directly translates to a formula of H₂S.

Inorganic Nomenclature

Inorganic nomenclature involves the rules and conventions for naming inorganic chemical compounds. Naming acids, specifically, has a set of guidelines that reflect the composition of the compound. For instance, when an acid's anion ends with '-ate', the acid name will end with '-ic acid' without adding 'hydro-'. For '-ite' ending anions, the acid name will end with '-ous acid', again without the prefix ‘hydro-’.

Hence, perbromic acid, which comes from the anion perbromate (BrO₄^-), is written as HBrO₄, and sulfurous acid with the sulfite ion (SO₃^2-) is written as H₂SO₃. Through these patterns, it becomes easier for students to deduce the formula of an acid from its name.

Polyatomic Ions

Polyatomic ions are ions composed of more than one atom. These ions are treated as a single charged entity when creating chemical formulas. Many acids are named based on their polyatomic ions. For instance, the polyatomic ion for chlorous acid is chlorite (ClO₂^-), which yields the formula HClO₂ for the acid.

It is vital to remember the names and formulas of common polyatomic ions since they are used frequently in both naming and writing the formulas for acids and other inorganic compounds. For example, perchlorate is ClO₄^-, and when it forms perchloric acid, the resulting formula is HClO₄.

Chemical Compounds

Chemical compounds are substances made from two or more different elements that are chemically bonded together. The formula for a compound reflects the elements that make it up and the proportions in which they are found. For example, acetic acid, a compound formed by carbon (C), hydrogen (H), and oxygen (O), is represented by CH₃COOH. Understanding the composition and structure of chemical compounds is fundamental to chemical nomenclature and is crucial for correctly writing chemical formulas.

In inorganic chemistry, recognizing whether a compound is an acid, base, salt, or another type is the first step in naming it correctly according to the rules of nomenclature. For this reason, closely studying the characteristics of acids and their corresponding anions can greatly enhance a student's ability to write and understand chemical formulas.