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Introduction to Acids and Bases

Introduction to Acids and Bases. Arrhenius Acids and Bases. Acids produce H + in aqueous solutions water HCl H + (aq) + Cl - (aq) Bases produce OH - in aqueous solutions water NaOH Na + (aq) + OH - (aq). Acids. Produce H + (as H 3 O + ) ions in water

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Introduction to Acids and Bases

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  1. Introduction to Acids and Bases

  2. Arrhenius Acids and Bases • Acids produce H+ in aqueous solutions water HCl H+(aq) + Cl- (aq) • Bases produce OH- in aqueous solutions water NaOH Na+(aq) + OH- (aq)

  3. Acids • Produce H+ (as H3O+) ions in water • Electrolytes • Taste sour • Corrode metals • React with bases to form salts and water

  4. Bases • Produce OH- ions in water • Taste bitter, chalky • Are electrolytes • Feel soapy, slippery • React with acids to form salts and water

  5. Learning Check AB1 Describe the solution in each of the following as: 1) acid 2) base or 3)neutral. A. ___soda B. ___soap C. ___coffee D. ___ wine E. ___ water F. ___ grapefruit

  6. Solution AB1 Describe each solution as: 1) acid 2) base or 3) neutral. A. _1_ soda B. _2_ soap C. _1_ coffee D. _1_ wine E. _3_ water F. _1_ grapefruit

  7. Learning Check AB2 Identify each as characteristic of an A) acid or B) base ____ 1. Sour taste ____ 2. Produces OH- in aqueous solutions ____ 3. Chalky taste ____ 4. Is an electrolyte ____ 5. Produces H+ in aqueous solutions

  8. Solution AB2 Identify each as a characteristic of an A) acid or B) base _A_ 1. Sour taste _B_ 2. Produces OH- in aqueous solutions _B_ 3. Chalky taste A, B4. Is an electrolyte _A_ 5. Produces H+ in aqueous solutions

  9. Some Common Acids HCl hydrochloric acid HNO3 nitric acid H3PO4 phosphoric acid H2SO4 sulfuric acid HC2H3O2 acetic acid

  10. Some Common Bases NaOH sodium hydroxide KOH potassium hydroxide Ba(OH)2 barium hydroxide Mg(OH)2magnesium hydroxide Al(OH)3 aluminum hydroxide

  11. Learning Check AB5 Acid, Base Name or Salt CaCl2 ______ _________________ KOH ______ _________________ Ba(OH)2 ______ _________________ HBr ______ _________________ H2SO4 ______ __________________

  12. Solution AB5 Acid, Base Name or Salt CaCl2 salt calcium chloride KOH base potassiuim hydroxide Ba(OH)2 base barium hydroxide HBr acid hydrobromic acid H2SO4 acid sulfuric acid

  13. Pure Water is Neutral Pure water contains small, but equal amounts of ions: H3O+ (H+) and OH- H2O + H2O H3O+ + OH- hydronium hydroxide ion ion H3O+ OH-

  14. Acids • Increase H+ (H3O+) • HCl (g) + H2O (l)H3O+(aq) + Cl-(aq) • More [H3O+] than water • As H3O+ increases, OH- decreases [H3O+] > [OH-] H3O+ OH-

  15. Acids Strong Acids (the big 7): Dissociate completely in water HCl, HBr, HI, HNO3, H2SO4, HClO4, HClO3 Weak acids: Only a few molecules dissociate HC2H3O2, HF, etc.

  16. Bases • Increase the hydroxide ions (OH-) • NaOH (s) Na+(aq) + OH- (aq) • More [OH-] than water, [OH-] • When OH- increases, H3O+ decreases [OH] > [H3O+] OH- H3O+

  17. Bases • Strong Bases (the big 8) Dissociate completely in water • Group I metal hydroxides • Heavier group II metal hydroxides Ca(OH)2, Ba(OH)2, Sr(OH)2 • Weak Bases • Only a few Molecules dissociate NH 3 (ammonia)

  18. pH • Indicates the acidity [H+] of the solution • pH = - log [H+] • From the French pouvoir hydrogene (“hydrogen power” or power of hydrogen)

  19. pH Range 0 1 2 3 4 5 6 7 8 910 11 12 13 14 Neutral [H+]>[OH-][H+] = [OH-][OH-]>[H+] Acidic Basic

  20. Some [H+] and pH [H+] pH 1 x 10-5 M 5 1 x 10-9 M 9 1 x 10-11M 11

  21. pH of Some Common Acids gastric juice 1.0 lemon juice 2.3 vinegar 2.8 orange juice 3.5 coffee 5.0 milk 6.6

  22. pH of Some Common Bases blood 7.4 tears 7.4 seawater 8.4 milk of magnesia 10.6 household ammonia 11.0

  23. Acid Rain • Unpolluted rain has a pH of 5.6 • Rain with a pH below 5.6 is “acid rain“ • CO2 in the air forms carbonic acid CO2 + H2O H2CO3 • Adds to H+ of rain H2CO3 H+ (aq) + HCO3-(aq) Formation of acid rain: 1. Emission of sulfur and nitrogen oxides from the burning of fuels expecially coal with high S content, power stations, oil refineries, vehicles as well as bacterial decomposition, and lighting hitting N2 SO2 26 million tons in 1980 NO and NO2 22 million tons in 1980 Mt. St Helens (1980) 400,000 tons SO2 2. Reactions in the atmosphere form SO3 2SO2 + O2 2 SO3 3. Reactions with atmosphere water form acids SO3 + H2O  H2SO4 sulfuric acid NO + H2O  HNO2 nitrous acid HNO2 + H2O  HNO3 nitric acid 4. Effects of Acid Rain Decline in fish populations in rivers and lasts due to toxic effect of Al leached from soil by acid rain Extensive fish kills in spring from runoff due to accumulation of large amounts of acid on the snow Dissolves minerals Mg, Ca, and K from the soil and waxy coatings that protect leaves from bacteria Corrodes metals, textiles, paper and leather

  24. Sources of Acid Rain • Power stations • Oil refineries • Coal with high S content • Car and truck emissions • Bacterial decomposition, and lightning hitting N2

  25. SO2 26 million tons in 1980 NO and NO2 22 million tons in 1980 Mt. St Helens (1980) 400,000 tons SO2 • Reactions with oxygen in air form SO3 2SO2 + O2 2 SO3 • Reactions with water in air form acids SO3 + H2O H2SO4 sulfuric acid NO + H2O HNO2 nitrous acid HNO2 + H2O HNO3 nitric acid

  26. Effects of Acid Rain • Leaches Al from soil, which kills fish • Fish kills in spring from runoff due to accumulation of large amounts of acid in snow • Dissolves waxy coatings that protect leaves from bacteria • Corrodes metals, textiles, paper and leather

  27. Neutralization Reactions When acid and bases with equal amounts of hydrogen ion H+ and hydroxide ions OH- are mixed, the resulting solution is neutral. NaOH (aq) + HCl(aq) NaCl + H2O base acid salt water Ca(OH)2 + 2 HCl CaCl2 + 2H2O base acid salt water

  28. Neutralization Reactions An acid/base reaction is a special form of a double displacement reaction

  29. Neutralization H+ and OH- combine to produce water H+ + OH- H2O from acid from base neutral

  30. Neutralization The cation from the base and the anion from the acid combine to form a salt. Acid + Base  Salt + water

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