Chapter 14. Acids and Bases

14.1 Acids • Produce H+ ions in water Chapter 14: Acids and Bases • Taste sour • Act Corrosive • Turn blue litmus paper red 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 • Turn red litmus paper blue • Bases produce OH- in aqueous solutions • 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+) 2 HNO3 + Ca(OH)2  2 H2O + Ca(NO3)2 Base is proton (H+) acceptor: (gains H+) _________ is the Arrhenius acid. __________ is the Arrhenius base. HCl loses H+ acid + NH3 gains H+ base NH4+ + Cl- 1 Molarity / Concentration [ ] means concentration or molarity; M = mol / L [H+] = mol/L of In pure water, [H+] > [OH-], H+ [H+] ions pH Scale 0 = [OH-] Neutral Strongly acidic 1 Weakly acidic 2 3 4 5 the solution is ??? 6 7 8 9 10 11 12 13 14 Basic Acidic [H+] < [OH-], the solution is ??? Strongly basic Weakly basic Neutral [H+]>[OH-] [H+] = [OH-] [OH-]>[H+] 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 = p pH of Some Common Items Substance Vomit (HCl) Lemon juice Coffee Saliva Blood Milk of Magnesia ammonia urine most colas Root Beer pH ~2 2.3 5.0 ~7 7.4 10.5 11.7 6 2.5-3.5 5.5 Enamel erosion occurs below pH of 5. What are you drinking? 2 Buffers Strengths of Acids and Bases A solution that resists changes in pH when a little acid or base is added to it. Strong acids ionize completely (~100%) in water. (learn these: HCl, HNO3, H2SO4) A buffer solution keeps the pH relatively constant. 1. Buffer systems are very important in body fluids. 2. Blood pH needs to stay around a pH value of 7.4 or you will die. HCl (aq)  H+ (aq) + Cl- (aq) Strong bases dissociate completely (~100%) in water to form ions . (learn these: KOH, NaOH) NaOH (aq)  Na+ (aq) + OH- (aq) Strong Acids and Bases  Acids:  HCl - hydrochloric acid  HNO3 - nitric acid  H2SO4 - sulfuric acid Weak Acids  Weak acids ionize very little (~1-5 %) in water: (learn these: HF, H2CO3, HC2H3O2, H3PO4) Ex: HC2H3O2 (aq) ⇌ H+ (aq) + C2H3O2- (aq)  Bases:  NaOH - sodium hydroxide  KOH - potassium hydroxide  What does strong mean?  Most do not break apart  only ~ 1-5 % (1-5 molecules in 100) of the acid has ionized or dissociated  What ions are produced in water for each? Weak Bases  Weak bases dissociate very little (~1-5%) so just a few ions are formed: (learn these: NH4OH, Mg(OH)2) Strong & Weak Acid & Base Which is a strong acid? Which is a weak acid? Which is a strong base? Ex: NH4OH (aq) ⇌ NH4+ (aq) + OH- (aq) 3 Drawings of Solutions Draw Pictures of HNO3, HF, KOH, and Mg(OH)2 in water. Summary  Arrhenius acids make H+ ions 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 In general: ACID + BASE  SALT + H2O HCl(aq) + NaOH (aq)  NaCl + H2O Salt = ionic compound Electrolytes 14.10 Electrolytes 1) Strong electrolyte - good conductor of electricity. Chemical completely ionizes in water. (all ions) • soluble ionic compounds, strong acids, strong bases • KBr, HNO3, KOH, NaCl 2) Weak Electrolyte - poor conductor of electricity. Chemical partly ionizes in water. (few ions) • 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 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  Try 1-3, 8, 10, 14  NaCl  Strong vs weak acid  Answers in Appendix J  HCl vs acetic acid  Strong vs weak base 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