Naming Acids: Binary Acids and Oxyacids

Naming Acids

Introduction to Acids

Acids are a fundamental class of compounds in chemistry, typically recognized as substances that release hydrogen ions (H+) when dissolved in water. The systematic naming of acids depends on their composition, particularly the presence of hydrogen and the type of anion bonded to it.

• Acid: Usually a covalent compound beginning with a hydrogen ion (H+).

• Covalent Compound: A compound that contains only nonmetal atoms bonded together.

Binary Acids

Definition and Formation

Binary acids are covalent compounds containing hydrogen bonded to a nonmetal anion that is not oxygen. These acids are named based on their two-element composition.

• General Formula: H + nonmetal (e.g., HCl, HBr)

Rules for Naming Binary Acids

1. Use the prefix hydro- to represent the H+ ion.

2. Use the base name of the nonmetal (e.g., chlor for Cl, phosphor for P).

3. Add the suffix -ic and the word acid.

Example: HCl is named hydrochloric acid.

Practice Problems

• H2S: hydrosulfuric acid

• HCN: hydrocyanic acid

Oxyacids

Definition and Formation

Oxyacids are covalent compounds containing hydrogen ions bonded to polyatomic ions that contain oxygen. The naming of oxyacids depends on the polyatomic ion present.

• General Formula: H + polyatomic ion (e.g., HNO3, H2SO4)

Rules for Naming Oxyacids

1. If the polyatomic ion ends with -ate, change the ending to -ic acid. Example: NO3- (nitrate) → HNO3 is nitric acid

2. If the polyatomic ion ends with -ite, change the ending to -ous acid. Example: NO2- (nitrite) → HNO2 is nitrous acid

Practice Problems

• HClO2: chlorous acid

• HC2H3O2: acetic acid

• H2CO3: carbonic acid

Summary Table: Naming Acids

Type of Acid	Formula Example	Naming Rule	Name Example
Binary Acid	HCl	hydro- + base name + -ic acid	hydrochloric acid
Oxyacid (-ate ion)	HNO3	base name + -ic acid	nitric acid
Oxyacid (-ite ion)	HNO2	base name + -ous acid	nitrous acid

Key Equations

• General formula for binary acid: $\mathrm{H}X$

• General formula for oxyacid: $\mathrm{H}_n\mathrm{XO}_m$

Additional info: Understanding acid nomenclature is essential for predicting chemical formulas from names and vice versa, which is a foundational skill in general chemistry.