Writing Names and Formulas for Acids 12.2 Lecture Notes 2 Essential Questions • 1. What are acids? How can you identify them? • 2. What are the two types of acids? • 3. How do you write chemical names and formulas for acids? 3 (1) Review – Acids (Arrhenius Def.) • Molecules that, when dissolved in water, produce H+ ions (protons) and an anion – Assumption is (aq) – means dissolved in water. If formula has (g) or (s), name as a non-acid. • Cation of an acid is always H+ 4 (2) Two Types of Acids • Those in which anion contains oxygen – AKA “oxyacid” – e.g., H2SO4 • Those in which anion does not contain oxygen – AKA “simple acids” – e.g., HF (3) Naming & Writing Formulas for 5 Simple Acids • Simple acids are usually H+ and a halogen • Start with the root word of anion. Add the prefix “hydro” & suffix “-ic acid” • Formula Name – HCl: Anion is chloride Hydrochloric acid • Name Formula – Hydroiodic acid: “hydro” tells you it’s a simple acid. “iodic” tells you the anion is iodine. H+ + I- --> HI (3) Naming & Writing Formulas for Simple Acids Cation Anion Formula Name HBr (aq) HI (aq) HF (aq) Hydrochloric Acid Hydrobromic Acid H2S (aq) H2Se (aq) 6 7 (4) Naming Oxyacids • Start w/the root word of anion, add new ending • “- ate” becomes “-ic acid” • If I ate it, I would say ick! (“- ate” “-ic acid”) Sauteed water beetles… yum –Example: HC2H3O2 - • Anion is C2H3O2 = Acetate becomes “Acetic Acid” (4) Naming Oxyacids • “- ite” becomes “-ous acid” • “She did it just to spite us.” (“- ite” “-ous acid”) – Example: H2SO3 2- • Anion is SO3 = Sulfite becomes “Sulfurous Acid” 9 (4) Naming Oxyacids 10 (5) Writing Formulas for Oxyacids • Identify the name of the anion – If it ends in “ic acid”, it’s the “–ate” version – If it ends in “ous-acid”, it’s the “–ite” version • Write anion formula. Cation is always H+. Do criss-cross to get acid formula. - – Acetic Acid Acetate C2H3O2 is the anion + - • H C2H3O2 HC2H3O2 2- – Sulfurous Acid Sulfite SO3 is the anion + -2 • H SO3 H2SO3 11 (5) Writing Formulas for Oxyacids Phosphorous acid Chlorous acid Phosphoric acid 12 (6) The Importance of (aq) If dissolved in H2O If not, name as a (aq), name as an acid Type I compound HF (aq) hydrofluoric acid HF Hydrogen fluoride HCl (aq) hydrochloric acid HCl Hydrogen chloride HBr (aq) hydrobromic acid HBr Hydrogen bromide HI (aq) hydroiodic acid HI Hydrogen iodide HCN (aq) hydrocyanic acid HCN Hydrogen cyanide H2S (aq) hydrosulfuric acid H2S Hydrogen sulfide H2Se (aq) hydroselenic acid H2Se hydrogen selenide H3PO4 (aq) phosphoric acid H3PO4 hydrogen phosphate.