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Acids and Bases

Learn about the properties, definitions, and reactions of acids and bases, including the Brønsted-Lowry concepts, common examples, and strength variances. Explore the pH scale, neutralization, and common substances on the scale.

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Acids and Bases

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  1. Acids and Bases http://www.unit5.org/chemistry/AcidBase.html

  2. Properties ACIDS BASES • electrolytes • electrolytes • bitter taste • sour taste • turn litmus red • turn litmus blue • react with metals to form H2 gas • slippery feel • vinegar, milk, soda, apples, citrus fruits • ammonia, lye, antacid, baking soda ChemASAP

  3. H H – + O O Cl Cl H H H H Definitions • Arrhenius - In aqueous solution… • Acidsform hydronium ions (H3O+) HCl+ H2O  H3O+ + Cl– acid Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  4. H H – + N O O N H H H H H H H H Definitions • Arrhenius - In aqueous solution… • Bases form hydroxide ions (OH-) NH3+ H2O  NH4+ + OH- base Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  5. Brønsted-Lowry Acids and Bases Acid = any substance that donates a proton. Base = any substance that accepts a proton. 1- 1+ d+ d- + Cl- H2O H3O+ HCl chloride ion (base) hydronium ion (acid)

  6. 1- 1+ + OH- NH4+ hydroxide ion ammonium ion Brønsted-Lowry Acids and Bases d- d+ H2O NH3 (acid) (base)

  7. Acid – Base Systems

  8. Common Acids Battery acid Sulfuric Acid H2SO4 Nitric Acid HNO3 Phosphoric Acid H3PO4 Hydrochloric Acid HCl Acetic Acid CH3COOH Carbonic Acid H2CO3 Used to make fertilizers and explosives Food flavoring Stomach acid Vinegar Carbonated water

  9. Common Bases Name Formula Common Name Sodium hydroxide NaOH lye or caustic soda Potassium hydroxide KOH lye or caustic potash Magnesium hydroxide Mg(OH)2 milk of magnesia Calcium hydroxide Ca(OH) 2 slaked lime Ammonia water NH3 H2O household ammonia . NH4OH NH41+ + OH1- ammonium hydroxide

  10. - + Strength • Strong Acid/Base • 100% ionized in water • strong electrolyte HCl HNO3 H2SO4 HBr HI HClO4 NaOH KOH Ca(OH)2 Ba(OH)2 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  11. - + Strength • Weak Acid/Base • does not ionize completely • weak electrolyte HF CH3COOH H3PO4 H2CO3 HCN NH3 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  12. Strong vs. Weak Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 508

  13. + 1- Acid Dissociation H Cl HCl Conjugate base Acid Conjugate pair Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 280

  14. HCl + H2O H3O+ + Cl- HCl + H2O H3O+ + Cl- acid base CA CB Conjugate Acid-Base Pairs conjugates base acid acid base conjugates

  15. NH3 + H2O NH41+ + OH- NH3 + H2O NH41+ + OH- base acid CA CB Conjugate Acid-Base Pairs conjugates acid base base acid conjugates

  16. Acid-Base Neutralization 1- 1+ + + OH- H2O H3O+ H2O Hydroxide ion Water Hydronium ion Water Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 584

  17. Neutralization of Bug Bites Red Ant - bites with acid Wasp - stings with base (neutralize with baking soda) (neutralize with lemon juice or vinegar)

  18. Neutralization ACID + BASE  SALT + WATER HCl + NaOH  NaCl + H2O strong strong neutral HC2H3O2 + NaOH  NaC2H3O2 + H2O weak strong basic • Salts can be neutral, acidic, or basic. • Neutralization does not mean pH = 7. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  19. Neutralization moles H3O+ = moles OH- MVn = MVn M: Molarity V: volume n: # of H+ ions in the acid or OH- ions in the base Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  20. pH scale : measures acidity/basicity Soren Sorensen (1868 - 1939) ACID BASE 10x 100x 10x 10x 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 NEUTRAL Each step on pH scale represents a factor of 10. pH 5 vs. pH 6(10X more acidic) pH 3 vs. pH 5 (100X different) pH 8 vs. pH 13 (100,000X different)

  21. [H+] pH 10-14 14 10-13 13 10-12 12 10-11 11 10-10 10 10-9 9 10-8 8 10-7 7 10-6 6 10-5 5 10-4 4 10-3 3 10-2 2 10-1 1 100 0 1 M NaOH Ammonia (household cleaner) 7 Acid Base 0 14 Blood Pure water Milk Acidic Neutral Basic Vinegar Lemon juice Stomach acid 1 M HCl pH Scale Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 515

  22. 10x log 2nd antilog pH = - log [H+] [H+] + [OH-] = 1 x 10-14M Given: determine the [hydronium ion] pH = 4.6 choose proper equation pH = - log [H+] substitute pH value in equation 4.6 = - log [H+] multiply both sides by -1 - 4.6 = log [H+] take antilog of both sides - 4.6 = log [H+] [H+] = 2.51x10-5M Recall, [H+] = [H3O+] You can check your answer by working backwards. pH = - log [H+] pH = - log [2.51x10-5M] pH = 4.6

  23. pH of Common Substance pH [H1+] [OH1-] pOH 14 1 x 10-14 1 x 10-0 0 13 1 x 10-13 1 x 10-1 1 12 1 x 10-12 1 x 10-2 2 11 1 x 10-11 1 x 10-3 3 10 1 x 10-10 1 x 10-4 4 9 1 x 10-9 1 x 10-5 5 8 1 x 10-8 1 x 10-6 6 6 1 x 10-6 1 x 10-8 8 5 1 x 10-5 1 x 10-9 9 4 1 x 10-4 1 x 10-10 10 3 1 x 10-3 1 x 10-11 11 2 1 x 10-2 1 x 10-12 12 1 1 x 10-1 1 x 10-13 13 0 1 x 100 1 x 10-14 14 NaOH, 0.1 M Household bleach Household ammonia Lime water Milk of magnesia Borax Baking soda Egg white, seawater Human blood, tears Milk Saliva Rain Black coffee Banana Tomatoes Wine Cola, vinegar Lemon juice Gastric juice More basic 7 1 x 10-7 1 x 10-7 7 More acidic

  24. Litmus Paper

  25. pH Paper pH 0 1 2 3 4 5 6 pH 7 8 9 10 11 12 13

  26. colorless pink phenolphthalein strong weak acid base yellowblue bromthymol blue strong acid base strong ROYGBIV universal indicator pH 4 7 12 Indicators litmus paper & pH paper

  27. Range and Color Changes of Some Common Acid-Base Indicators pH Scale 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Indicators Methyl orange red 3.1 – 4.4 yellow Methyl red red 4.4 6.2 yellow Bromthymol blue yellow 6.2 7.6 blue Neutral red red 6.8 8.0 yellow Phenolphthalein colorless 8.0 10.0 red colorless beyond 13.0 Bromthymol blue indicator would be used in titrating a strong acid with a strong base. Phenolpthalein indicator would be used in titrating a weak acid with a strong base. Methyl orange indicator would be used in titrating a strong acid with a weak base.

  28. Titration • Equivalence point (endpoint) • Point at which equal amounts of H3O+ and OH- have been added. • Determined by… • indicator color change • dramatic change in pH Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  29. Titration moles H3O+ = moles OH- MVn = MVn M: Molarity V: volume n: # of H+ ions in the acid or OH- ions in the base Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  30. Titration • 42.5 mL of 1.3M KOH are required to neutralize 50.0 mL of H2SO4. Find the molarity of H2SO4. H3O+ M = ? V = 50.0 mL n = 2 OH- M = 1.3M V = 42.5 mL n = 1 MV# = MV# M(50.0mL)(2) =(1.3M)(42.5mL)(1) M = 0.55M H2SO4 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

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