Acids and Bases: Definitions, Classification, and Nomenclature

Acids and Bases

Definitions and Behavior

Acids and bases are fundamental chemical species with distinct behaviors in aqueous solutions. Understanding their definitions and how they interact is essential for mastering general chemistry.

• Acids: Compounds that have a loosely held hydrogen atom that can be donated to another compound in the form of a proton (H+). Acids are proton donors.

• Bases: Compounds that accept an incoming proton. Bases are proton acceptors.

• To form H+, a hydrogen atom loses its electron, leaving only a proton.

Example: The hydrogen cation (H+) consists of a single proton.

Acid-Base Reactions

Acid-base reactions typically involve the transfer of a proton from the acid to the base, resulting in the formation of water and a salt. This is known as a neutralization reaction.

• General Equation:

$\mathrm{HA} + \mathrm{OH}^- \rightarrow \mathrm{A}^- + \mathrm{H_2O}$

• Example:

$\mathrm{HCl} + \mathrm{OH}^- \rightarrow \mathrm{Cl}^- + \mathrm{H_2O}$

• Most acids have formulas that begin with "H" (e.g., HCl, HNO3, H2SO4, H2CO3).

Classification of Acids

Types of Acids

Acids can be classified based on their composition into two main categories:

• Mineral Acids (Binary Acids): Contain hydrogen and one other element.

• Oxyacids: Contain hydrogen, oxygen, and at least one other element.

Naming Acids

Naming Mineral (Binary) Acids

Mineral acids are named based on the monoatomic anion they contain. The naming process involves several steps:

• Identify the name of the monoatomic anion in the acid.

• Remove the -ide suffix from the anion name and replace it with -ic.

• Attach the prefix hydro-.

• Pair this name with the word "acid".

Examples:

• HCl: hydrochloric acid

• HBr: hydrobromic acid

• H2S: hydrosulfuric acid

Naming Oxyacids

Oxyacids are named based on the polyatomic (oxyanion) they contain. The naming rules are as follows:

• Do not include the prefix hydro- in the acid name.

• Identify the polyatomic anion (oxyanion) in the acid.

• If the oxyanion name ends in -ate, replace this suffix with -ic.

• If the oxyanion name ends in -ite, replace this suffix with -ous.

• Add the word "acid" to the name.

Examples:

• H2SO4: sulfuric acid (from sulfate)

• HNO3: nitric acid (from nitrate)

• HNO2: nitrous acid (from nitrite)

• H3PO4: phosphoric acid (from phosphate)

• HClO: hypochlorous acid (from hypochlorite)

Writing Formulas for Acids

Formulas for Mineral Acids

To write the formula for a mineral acid:

• Recognize the hydro- prefix, indicating a monoatomic anion.

• Determine the monoatomic ion in the acid.

• Write out the formulas for a proton (H+) and the monoatomic anion.

• Balance the charges to write the correct formula.

Examples:

• Hydroiodic acid: H+ + I- → HI

• Hydrofluoric acid: H+ + F- → HF

• Hydroselenic acid: 2H+ + Se2- → H2Se

Formulas for Oxyacids

To write the formula for an oxyacid:

• Examine the name before the word "acid".

• If the name ends in -ic, the oxyanion name ends in -ate.

• If the name ends in -ous, the oxyanion name ends in -ite.

• Write down the formula for a proton and the oxyanion.

• Balance the charges to write the correct formula.

Examples:

• Nitric acid: H+ + NO3- → HNO3

• Phosphorous acid: 3H+ + PO33- → H3PO3

• Perchloric acid: H+ + ClO4- → HClO4

Summary Table: Acid Nomenclature

Type of Acid	Naming Rule	Example Name	Formula
Mineral (Binary) Acid	hydro- + [anion root] + -ic acid	Hydrochloric acid	HCl
Oxyacid (from -ate)	[anion root] + -ic acid	Sulfuric acid	H2SO4
Oxyacid (from -ite)	[anion root] + -ous acid	Nitrous acid	HNO2

Review Questions

Sample Questions

• Write the formula for each of the following acids: nitric acid, chloric acid, acetic acid, hydroiodic acid, sulfurous acid, dichlorous acid, phosphoric acid, hydrobromic acid, nitrous acid, hydrochloric acid, perchloric acid, hydrofluoric acid, carbonic acid, sulfuric acid.

• Name each of the following acids: HNO3, H3PO3, H2SO4, H2CO3, H2SO3, HClO2, H3PO4, HBr, HCl, HF, HClO4, HNO2, HI, H2Se, HClO, H2S.

Additional info: This guide covers the core concepts of acid and base definitions, classification, and nomenclature, which are essential for understanding acid-base chemistry in general chemistry courses.