14.1 Acids • Produce H+ ions in water Chapter 14: • Taste sour Acids and Bases • Act Corrosive • Turn blue litmus paper red CHM 130 GCC Chemistry http://www.wisc-online.com/Objects/ViewObject.aspx?ID=GCH6204 http://phet.colorado.edu/en/simulation/acid-base-solutions 14.2 Bases 14.2 Arrhenius Acids and Bases • Produce OH- ions in water • Acids produce H+ in aqueous solutions • Taste bitter, chalky • HCl (aq) H+ (aq) + Cl- (aq) • Feel soapy, slippery • Bases produce OH- in aqueous solutions • Turn red litmus paper blue • NaOH (aq) Na+ (aq) + OH- (aq) Arrhenius Acids and Bases 14.3 Bronsted-Lowry Acids and Bases Which is the acid and which is the base? Acid is proton (H+) donor: (loses H+) Base is proton (H+) acceptor: (gains H+) 2 HNO3 + Ca(OH)2 2 H2O + Ca(NO3)2 _________ is the Arrhenius acid. + - HCl + NH3 NH4 + Cl loses H+ gains H+ __________ is the Arrhenius base. acid base 1 Molarity / Concentration pH Scale [ ] means concentration or molarity; M = mol / L Neutral Strongly Strongly Weakly Weakly basic [H+] = mol/L of H+ ions acidic acidic basic In pure water, [H+] = [OH-] 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 [H+] > [OH-], the solution is ??? Acidic Basic [H+] < [OH-], the solution is ??? Neutral + + - - http://phet.colorado.edu/en/simulation/molarity [H ]>[OH-] [H ] = [OH ] [OH ]>[H+] http://phet.colorado.edu/en/simulation/ph-scale pH of Some Common Items pH Scale pH = -log[H+] or [H+] =10-pH [H+] = 10-1 or 0.1mol/L so pH = [H+] = 10-5 mol/L………... pH = [H+] = 10-8 mol/L ………... pH = [H+] = 10-3 mol/L …………pH = [H+] = 0.001 mol/L ……… pH = [H+] = 0.00000001 mol/L.. pH = http://chemwiki.ucdavis.edu/@api/deki/files/8232/639px-PH scale.png pH of Some Common Items Substance pH Enamel erosion Vomit (HCl) ~ 2 occurs below pH Lemon juice 2.3 Coffee 5.0 of 5. What are Saliva ~ 7 you drinking? Blood 7.4 Milk of Magnesia 10.5 ammonia 11.7 urine 6 most colas 2.5-3.5 Root Beer 5.5 2 Buffers Strengths of Acids and Bases A solution that resists changes in pH when a little Strong acids ionize completely (~100%) in acid or base is added to it. water. (learn these: HCl, HNO3, H2SO4) A buffer solution keeps the pH relatively constant. HCl (aq) H+ (aq) + Cl- (aq) 1. Buffer systems are very important in body fluids. Strong bases dissociate completely (~100%) 2. Blood pH needs to stay around a pH value of in water to form ions . (learn these: KOH, 7.4 or you will die. NaOH) NaOH (aq) Na+ (aq) + OH- (aq) Strong Acids and Bases Weak Acids Acids: Weak acids ionize very little (~1-5 %) in HCl - hydrochloric acid water: (learn these: HF, H2CO3, HC2H3O2, HNO - nitric acid 3 H3PO4) H2SO4 - sulfuric acid + - Bases: Ex: HC2H3O2 (aq) ⇌ H (aq) + C2H3O2 (aq) NaOH - sodium hydroxide KOH - potassium hydroxide Most do not break apart only ~ 1-5 % (1-5 molecules in 100) of the What does strong mean? acid has ionized or dissociated What ions are produced in water for each? Weak Bases Strong & Weak Acid & Base Weak bases dissociate very little (~1-5%) so just a few ions are formed: (learn these: Which is a strong acid? NH OH, Mg(OH) ) Which is a weak acid? 4 2 Which is a strong base? + - Ex: NH4OH (aq) ⇌ NH4 (aq) + OH (aq) 3 Drawings of Solutions Summary + Draw Pictures of HNO3, HF, KOH, and Arrhenius acids make H ions in water Mg(OH)2 in water. Arrhenius bases make OH- ions in water Bronsted-Lowry acids lose H+ Bronsted-Lowry bases gain H+ Buffers keep pH constant Strong acids and bases ionize 100% Weak acids and bases ionize very little Neutralization Reactions 14.10 Electrolytes 1) Strong electrolyte - good conductor of electricity. In general: ACID + BASE SALT + H2O Chemical completely ionizes in water. (all ions) • soluble ionic compounds, strong acids, strong bases • KBr, HNO , KOH, NaCl HCl(aq) + NaOH (aq) NaCl + H2O 3 2) Weak Electrolyte - poor conductor of electricity. Chemical partly ionizes in water. (few ions) Salt = ionic compound • weak acids, weak bases, insoluble ionic solids • HF, Mg(OH)2, AgCl, H2CO3 3) Nonelectrolyte - non-conductor of electricity. (no ions) • Covalent compounds (no ions) • H2O, CO, C6H12O6 Electrolytes Strong, Weak, and Non-Electrolytes? Label the following as strong, weak, or non-electrolytes BaS AgCl KNO3 H2CO3 CO2 LiOH CaCO3 C6H12O6 Na3PO4 PbSO4 4 Electrolytes, Acid-Base Videos Chapter 14 Self-Test, p. 437 NaCl Try 1-3, 8, 10, 14 http://www.youtube.com/watch?v=aELPrWzixeU Answers in Appendix J Strong vs weak acid http://www.youtube.com/watch?v=kcPjY9cQpWs&feature=related HCl vs acetic acid http://www.youtube.com/watch?v=NdG3wK9kNcg&feature=related Strong vs weak base http://www.youtube.com/watch?v=Av1LUAPN5q8&feature=related For Fun Blood pH needs to be between 7.35 and 7.45 - Maintained by CO2 / HCO3 buffer system Breathing can affect change in this system in seconds Acidosis is excess acid. Results in heavy breathing, weakness, headache, coma, and pH < 6.8 = death. Alkalosis is excess base. Results in convulsions, muscular weakness, and pH > 7.8 = death Partial pressure of CO2 normal is 35-45 mmHg High PCO2 means acidosis (lots of CO2 in blood) Low PCO2 means alkalosis (little CO2 in blood) + - Buffer rxn: CO2 + H2O ⇄ H2CO3 ⇄ H + HCO3 5.