Overview
This lecture covers the nomenclature of acids, including how to identify and name acids with and without oxygen, rules for converting names to formulas, and key patterns to remember for exams.
Identifying Acids
- Acids always have hydrogen (H) as the first element in their formula.
- Acids are typically written with "(aq)" to indicate they are dissolved in water (aqueous phase).
- Only name compounds as acids when they are in the aqueous phase.
Naming Acids Without Oxygen
- If the acid contains no oxygen, use the prefix "hydro-" and the suffix "-ic acid."
- The base name comes from the nonmetal element, with the "-ide" ending replaced by "-ic."
- Example: HBr (aq) is "hydrobromic acid"; HCl (aq) is "hydrochloric acid"; HCN (aq) is "hydrocyanic acid."
Naming Acids With Oxygen (Oxoacids)
- Identify the polyatomic (oxoanion) root, which contains oxygen.
- If the anion ends in "-ate," change it to "-ic acid" (no "hydro-" prefix).
- If the anion ends in "-ite," change it to "-ous acid" (no "hydro-" prefix).
- Example: HClO3 (aq) is "chloric acid" (from chlorate); HClO2 (aq) is "chlorous acid" (from chlorite); H2CO3 (aq) is "carbonic acid" (from carbonate); HBrO (aq) is "hypobromous acid" (from hypobromite).
Converting Acid Names to Formulas
- For acids, the word "acid" signals to write H as the first element.
- No "hydro-" prefix means an oxoacid; determine the corresponding polyatomic ion.
- "-ic acid" corresponds to "-ate" ion; "-ous acid" corresponds to "-ite" ion.
- Add enough H+ ions to balance the negative charge of the anion.
- Always write "(aq)" for aqueous phase.
- Example: "sulfuric acid" → sulfate ion (SO4^2-) → H2SO4 (aq).
- Example: "hydroiodic acid" → iodide ion (I^-) → HI (aq).
Practice & Examples
- Practice identifying and naming acids and converting between names and formulas.
- Example: HIO2 (aq) = iodite ion → "iodous acid."
- Example: HCl (aq) = chloride ion → "hydrochloric acid."
- Example: "nitrous acid" = nitrite ion (NO2^-) → HNO2 (aq).
Key Terms & Definitions
- Acid — Compound with hydrogen as the first element, capable of losing a proton in aqueous solution.
- Aqueous (aq) — Dissolved in water.
- Oxoanion — A negatively charged ion containing oxygen.
- Hydro- Prefix — Used for acids without oxygen.
- -ic acid Suffix — Used for acids derived from "-ate" anions.
- -ous acid Suffix — Used for acids derived from "-ite" anions.
Action Items / Next Steps
- Practice naming and writing formulas for acids (with and without oxygen).
- Memorize common polyatomic ions and their charges.
- Complete textbook exercises on acid nomenclature.