Chemistry Unit 5: Chemical Names & Formulas B-Level Lecture Naming Acids Chemistry Unit 5: Chemical Names & Formulas B-Level Lecture

Objectives Write the names of acids from their chemical formulas. Write the chemical formulas of acids from their names.

What Are Acids? An acid is a compound that produces hydrogen ions (H+) when dissolved in water. Acids usually take the form H“X” where “X” is an anion (either monatomic or polyatomic) Example: HCl Hydrogen chloride when pure Hydrochloric acid when dissolved in water

Writing Names From Formulas The name of an acid depends on the ending of the anion To locate the anion, “separate” the formula between the hydrogen(s) and the “rest” of the formula. The “rest” of the formula is the anion

Practice Identifying Anions HCl Cl  Cl- = chloride ion H2SO3 SO3  SO32- = sulfite ion HNO3 NO3  NO3- = nitrate ion

Naming Acids: Rule 1 If the name of the anion ends in –ide… HCl Cl  Cl- = chloride ion The name begins with the prefix hydro- The anion changes its ending to –ic The hydro ic is followed by the word acid hydrochloric acid

Naming Acids: Rule 2 If the name of the anion ends in –ite… H2SO3 SO3  SO32- = sulfite ion The anion changes its ending to –ous The ous is followed by the word acid sulfurous acid

Naming Acids: Rule 3 If the name of the anion ends in –ate… HNO3 NO3  NO3- = nitrate ion The anion changes its ending to –ic… The ic is followed by the word acid nitric acid

Practice Name the following acids: HF HClO H3PO4 hydrofluoric acid hypochlorous acid ClO hypchlorite phosphoric acid

Writing Formulas From Names The Three Rules work in reverse… If the acid ends in –ic AND starts with hydro- then the anion ending was –ide. If the acid ends in –ous then the anion ending was –ite. If the acid ends in –ic then the anion ending was –ate.

Acids Contain Anions!! Because acids are “ionic”, you have to make sure the overall charges balance when writing the formula! Use the name of the acid to determine the name of the anion Use the name of the anion and either the Periodic Table OR the Golden Sheet to determine the symbol(s) and charge of the anion Remember that the symbol and charge of the hydrogen ion is H+1 Determine the number of hydrogen ions and anions are required to make the overall charges balance Write the formula for the acid

Acid Formulas: Rule 1 If the name of the acid starts with –hydro and ends in –ic… hydrochloric acid The name of the anion was chloride The symbol and charge for chloride is Cl-1 The symbol and charge for hydrogen is H+1 It will only take one H and one Cl to balance the overall charges HCl

Acid Formulas: Rule 2 If the name of the acid ends in –ous… sulfurous acid The name of the anion was sulfite The symbol and charge for sulfite is SO32- The symbol and charge for hydrogen is H+1 It will only take two H and one SO3 to balance the overall charges H2SO3

Acid Formulas: Rule 3 If the name of the acid ends in –ic… nitric acid The name of the anion was nitrate The symbol and charge for nitrate is NO3- The symbol and charge for hydrogen is H+1 It will only take one H and one NO3 to balance the overall charges HNO3

Practice Write the formula for the following acids: hydrobromic acid arsenic acid nitrous acid HBr AsO4 3-; SO3 2- H3AsO4 HNO2

Processing Activity Naming Acids Anion Ending Example Acid Name -ide Cl- chloride hydro-(stem)-ic acid hydrochloric acid -ite SO32- sulfite (stem)-ous acid sulfurous acid -ate NO3- nitrate (stem)-ic acid nitric acid

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