Chapter 7 Acids and Bases: Please Pass the Protons

Chapter 72 Acid Causes litmus indicator dye to turn red Tastes sour –DO NOT TASTE UNKNOWN CHEMICALS Dissolves active metals to produce H 2 Reacts with bases to produce water and salt Base Causes litmus indicator dye to turn blue Tastes bitter –DO NOT TASTE UNKNOWN CHEMICALS Feels slippery on skin Reacts with acids to form water and salt

Chapter 73 Ionization When a compound breaks apart in aqueous solution HCl(aq)  H + (aq) + Cl – (aq) Common property of both acids and bases Also occurs with some salts

Chapter 74 Arrhenius Theory of Acids Acid: molecular substance that breaks up in aqueous solution into H + and anions H + - “hydrogen ions” or “protons” H + gives acid its properties Example: HNO 3 (aq)  H + (aq) + NO 3 – (aq) Common Acids

Chapter 75 Arrhenius Theory of Bases Base: releases OH – ions in aqueous solution OH – - hydroxide OH – gives bases their properties Example: NaOH(aq)  Na + (aq) + OH – (aq) Common Bases

Chapter 76 Limitations of Arrhenius Theory H + does not exist in solution More likely to find H + attached to H 2 O –H3O+–H3O+ NH 3 is a base –Does not contain OH –

Chapter 77 Brønsted–Lowry Acid–Base Theory Acid: proton (H + ) donor HCl + NH 3  NH Cl – HCl donates a H + to NH 3 –H + does not exist by itself Bases: accept a proton H 2 O + NH 3  NH OH – NH 3 accepts a H + from HCl

Chapter 78 Acidic Anhydrides React with water to form acids Typically are nonmetal oxides CO 2 + H 2 O  H 2 CO 3

Chapter 79 Basic Anhydrides React with water to form bases Typically are metal oxides CaO + H 2 O  Ca(OH) 2

Chapter 710 Strong and Weak Acids Strong acid: acid completely reacts with water –Completely ionizes in water Weak acid: acid reacts only slightly with water –Partially ionizes in water Common strong acids: HCl, HNO 3, H 2 SO 4 Most other acids are weak acids Strong and Weak Bases Strong base: base completely ionizes in water Weak base: only slightly ionizes in water Common strong bases: NaOH and KOH –True for most Group 1A and 2A hydroxides Common weak base: NH 3

Chapter 711 Amphiprotic A substance that can either donate or accept a proton H 2 O most common amphiprotic substance Reacts with base: H 2 O + NH 3  NH OH – Reacts with acid: H 2 O + HCl  Cl – + H 3 O +

Chapter 712 Neutralization Reaction of an acid and a base Acid + base  water + salt

Chapter 713 pH Scale Typical values range from 0 to 14 pH = 7 – neutral pH > 7 – basic pH < 7 – acidic

Chapter 714 pH in Common Solutions

Chapter 715 pH Calculations pH means to represent the concentration of H + in solution pH = –log [H + ]

Chapter 716 Practice pH Problems

Chapter 717 Acid Rain Normal rain: pH 5.6–6.5 Acid rain: pH < 5.6 Caused by acidic anhydrides released from burning fossil fuels Involves both air and water pollution Stomach Acids Stomach excretes HCl –Aids digestion of food Hyperacidity: too much HCl –Caused by emotional stress or overindulgence Remove excess acid using a base –Principle behind antacids –Too much base may give alkalosis

Chapter 718 Antacids May contain one of the following bases 1.NaHCO 3 Baking soda Safe and effective Not recommended for people with high blood pressure 2.CaCO 3 Effective Should not be used for long periods of time 3. Al(OH) 3 Similar behavior to CaCO 3 4.Mg(OH) 2 “milk of magnesia” Some brands of antacids are combinations of the above chemicals

Chapter 719 Acids in Industry H 2 SO 4 –Leading chemical product in U.S. –Used to make fertilizers –Found in car batteries HCl –Muriatic acid –Removes rust from metal –Removes lime from fixtures Bases in Industry NaOH – lye –Found in household cleaners CaO –Lime –Used to make mortar and cement

Chapter 720 Acids, Bases, and Health Concentrated acids and bases are corrosive poisons –May break down fabric or skin –May release heat Strong acids break down proteins –True for dilute solutions

Chapter 721 Acids and Bases in the Body Stomach acid –Aids digestion –Neutralized before entering rest of digestive system Blood –Maintains narrow pH range –Required for normal functioning of body