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Ch. 15 ACIDS & BASES GCC CHM 130

Ch. 15 ACIDS & BASES GCC CHM 130. 15.1 Acids. Produce H + ions in water Taste sour Act Corrosive Turn blue litmus paper red. Bases. Produce OH - ions in water Taste bitter, chalky Feel soapy, slippery Turn red litmus paper blue.

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Ch. 15 ACIDS & BASES GCC CHM 130

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  1. Ch. 15ACIDS & BASESGCCCHM 130

  2. 15.1 Acids • Produce H+ ions in water • Taste sour • Act Corrosive • Turn blue litmus paper red

  3. Bases • Produce OH- ions in water • Taste bitter, chalky • Feel soapy, slippery • Turn red litmus paper blue

  4. [ ] means concentration or molarity in units (moles / L) [H+] = mol / L of H+ ions In pure water, [H+] = [OH-] = same [H+] > [OH-], the solution is ???. [H+] < [OH-], the solution is ??? AcidicBasic

  5. pH Scale Neutral Strongly basic Strongly acidic Weakly basic Weakly acidic 0 1 2 3 4 5 6 7 8 910 11 12 13 14 Neutral [H+]>[OH-][H+] = [OH-][OH-]>[H+] Acidic Basic

  6. pH = -log[H+] or [H+] =10-pH [H+] = 10-1 or 0.1mol/L so pH = 1 [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 = 58338

  7. pH of Some Common Materials Substance pH Vomit (HCl) ~ 2 Lemon juice 2.3 Coffee 5.0 Saliva ~ 7 Blood 7.4 Milk of Magnesia 10.5 ammonia 11.7 urine 6 most colas 2.5-3.5 Root Beer 5.5

  8. Buffers • A solution that resists changes in pH when a little acid or base is added to it.So it keeps the pH constant. • Buffer systems are very important in body fluids. • Blood pH needs to stay around a pH value of 7.4 or you will die.

  9. 15.2 Arrhenius Acids and Bases • Acids produce H+ in aqueous solutions HCl (aq)  H+ + Cl- • Bases produce OH- in aqueous solutions NaOH (aq)  Na+ + OH-

  10. Strengths of Acids and Bases Strong acids ionize completely (~100%) in water. (learn these: HCl, HNO3, H2SO4) HCl (aq)  H+ + Cl- Strong bases dissociate completely (~100%) in water to form ions. (learn these: KOH, NaOH) NaOH (aq)  Na+ + OH-

  11. WEAK ACIDS • Weak acids ionize very little (~1 %) in water: (learn these: HF, H2CO3, HC2H3O2, H3PO4) Ex: HC2H3O2 (aq) D H+ + C2H3O2- • Most do not break apart • only ~ 1 % of the acid has ionized

  12. WEAK BASES • Weak bases dissociate very little (~1%) so just a few ions are formed: (learn these: NH4OH, Mg(OH)2) Ex: NH4OH (aq) D NH4+ (aq) + OH- (aq)

  13. AB,C none Which is a strong acid? Which is a weak acid?Which is a strong base?

  14. Neutralization Reactions In general ACID + BASE  SALT + H2O HCl(aq) + NaOH (aq)  NaCl + H2O Salt = ionic compound

  15. 2 HNO3 + Ca(OH)2 2 H2O + Ca(NO3)2 _________is the Arrhenius acid, and __________ is the Arrhenius base HNO3 Ca(OH)2

  16. Strong Acids and Bases • Acids: • HCl hydrochloric acid • HNO3 nitric acid • H2SO4 sulfuric acid • Bases: • NaOH sodium hydroxide • KOH potassium hydroxide • What does strong mean again??? • What ions are produced in water for each??

  17. Draw Pictures of HNO3, HF, KOH, and Mg(OH)2 in water on the board

  18. 15.3 Bronsted-Lowry Acids - Bases Acid is proton (H+) donor: (loses H+) Base is proton (H+) acceptor: (gains H+) HCl + NH3 NH4+ + Cl- loses H+ gains H+ acid base

  19. Summary • Buffers keep pH constant • Arrhenius acids make H+ ions in water • Arrhenius bases make OH- ions in water • Bronsted-Lowry acids lose H+ • Bronsted-Lowry bases gain H+ • Strong acids ionize 100% • Weak acids ionize way less • Strong bases dissociate 100% • Weak bases dissociate way less

  20. Enamel erosion occurs below pH of 5. What are you drinking?

  21. Acidic Beverages Erode Teeth

  22. 15.10 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 • Nonelectrolyte - non-conductor of electricity. - Covalent compounds (no ions) - H2O, CO, C6H12O6 3) 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

  23. Electrolyte ImagesWhich is strong, weak, non?

  24. Electrolyte & Acid Base Videos • NaCl http://www.youtube.com/watch?v=aELPrWzixeU • 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 • Strong vs weak acid http://www.youtube.com/watch?v=kcPjY9cQpWs&feature=related

  25. 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 D H2CO3D H+ + HCO3-

  26. Self Test • Page 445 • Try 1-3, 8, 10 • Answers in Appendix J

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