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Acids and Bases

Acids and Bases. Properties of Acids. Acids taste sour Acids effect indicators Blue litmus turns red Methyl orange turns red Acids have a pH lower than 7 Acids are proton (hydrogen ion, H + ) donors Acids react with active metals, produce H 2 Ex: Reactions lab

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Acids and Bases

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  1. Acids and Bases

  2. Properties of Acids • Acids taste sour • Acids effect indicators • Blue litmus turns red • Methyl orange turns red • Acids have a pH lower than 7 • Acids are proton (hydrogen ion, H+) donors • Acids react with active metals, produce H2 • Ex: Reactions lab • Acids react with carbonates to produce CO2 • Acids neutralize bases

  3. Acids Effect Indicators Acid Base Blue litmus paper turns red in contact with an acid.

  4. Acids Neutralize Bases

  5. Effects of Acid Rain on Marble(calcium carbonate) George Washington: BEFORE George Washington: AFTER

  6. Acids React with Active Metals Magnesium Acids react with active metals to form salts and hydrogen gas. Mg + 2HCl  MgCl2 + H2(g)

  7. Acids Taste Sour.

  8. Dilutions of AcidsALWAYS ADD ACID TO WATERThis reduces the chance that it will blow up in your face due to the heat of reaction making steam rapidly. The denser acid will sink and disperse more evenly.

  9. Binary Acids • An acid that contains hydrogen and one other element.

  10. Naming Binary Acids The proper method to use when naming binary acids is to begin with the hydro- prefix, use the root of the nonmetal, and add the –ic suffix.

  11. Oxyacids • An oxyacid is a compound of hydrogen, oxygen, and a third element, usually a nonmetal.

  12. Method for Naming Oxyacids • If the acid consists of one more oxygen than the polyatomic ion with the -ate suffix, use the per- prefix, the root of the polyatomic ion and the –ic suffix. • Example HClO4 = perchloric acid • If the acid consists of a polyatomic ion with the -ate suffix, use the root of the polyatomic ion and add –ic. • Example HClO3 = chloric acid • If the acid consists of hydrogen and a polyatomic ion with the -ite suffix, use the root of the polyatomic ion and add –ous. • Example HClO2 = chlorous acid • If an acid consists of one less oxygen than the polyatomic ion ending in –ite, use the hypo prefix, the root of the polyatomic ion and the –ous suffix. • Example HClO = hypochlorouc acid

  13. Naming Acids Anion Acid _________ ide (chloride, Cl1-) Hydro____ ic acid (hydrochloric acid, HCl) add H+ ions _________ic acid (chloric acid, HClO3) (perchloric acid, HClO4) _________ ate (chlorate, ClO3-) (perchlorate, ClO4-) add H+ ions _________ite (chlorite, ClO2-) (hypochlorite, ClO-) ______ous acid (chlorous acid, HClO2) (hypochlorous acid, HClO) add H+ ions

  14. Name the Acid

  15. Acids you must know: Strong Acids Sulfuric acid, H2SO4 Hydrochloric acid, HCl Nitric acid, HNO3 Weak Acids Phosphoric acid, H3PO4 Acetic acid, CH3COOH

  16. Sulfuric Acid • Highest volume production of any chemical in the U.S. • Used in the production of paper • Used in production of fertilizers • Used in petroleum refining

  17. Nitric Acid • Used in the production of fertilizers • Used in the production of explosives • Nitric acid is a volatile acid – its reactive components evaporate easily • Stains proteins (including skin!)

  18. Hydrochloric Acid • Used in the pickling of steel • Used to purify magnesium from sea water • Part of gastric juice, it aids in the digestion of protein • Sold commercially as “Muriatic acid”

  19. Muriatic Acid (HCl) • Sold commercially • Useful for cleaning concrete • Buyer beware

  20. Phosphoric Acid • A flavoring agent in sodas • Used in the manufacture of detergents • Used in the manufacture of fertilizers • Not a common laboratory reagent

  21. Acetic Acid • Used in the manufacture of plastics • Used in making pharmaceuticals • Acetic acid is the acid present in vinegar

  22. Strength of Acids Acids are proton (hydrogen ion, H+) donors Strong acids are assumed to be 100% ionized in solution (good proton donors). Weak acids are usually less than 5% ionized in solution (poor proton donors).

  23. Acids are Proton Donors Monoprotic acids Diprotic acids Triprotic acids H3PO4 HCl H2SO4 HC2H3O2 H2CO3 HNO3

  24. Comparison of a Monoprotic Acid to a Diprotic Acid

  25. Strong acids such as HCl ionize almost completrly in solution, forming hydronium ions, H3O+ H2O + HCl  H3O+ + Cl- Proton acceptor Proton donor

  26. Weak acids favor reverse reactions and enter chemical equilibrium before many hydronium ions, H3O+ form.

  27. Organic Acids Organic acids all contain the “carboxyl” group, sometimes several of them. The carboxyl group is a poor proton donor, so ALL organic acids are weak acids.

  28. Examples of Organic Acids • Citric acid in citrus fruit • Malic acid in sour apples • Deoxyribonucleic acid, DNA • Amino acids, the building blocks of protein • Lactic acid in sour milk and sore muscles • Butyric acid in rancid butter

  29. The pH scale is used to measure the strength of an acid or base. A pH of less than 7 indicates an acid. The lower the pH, the stronger the acid.

  30. pH of Many Common Substances

  31. Properties of Bases • Bases taste bitter • Bases effect indicators • Red litmus turns blue • Phenolphthalein turns purple • Bases have a pH greater than 7 • Bases are proton (hydrogen ion,H+) acceptors • Solutions of bases feel slippery • Bases neutralize acids

  32. Bases Effect Indicators Red litmus paper turns blue in contact with a base. Phenolphthalein turns purple in a base.

  33. Bases Have a pH of greater than 7.The greater the pH, the stronger the base.

  34. Bases Feel Slippery and Taste Bitter

  35. Bases Neutralize Acids Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl. 2 HCl + Mg(OH)2 MgCl2 + 2 H2O

  36. Examples of Bases • Sodium hydroxide (lye, Drano), NaOH • Potassium hydroxide, (Caustic Potash) KOH • Magnesium hydroxide, (milk of magnesia) Mg(OH)2 • Calcium hydroxide (lime), Ca(OH)2

  37. Different Acid-Base Definitions

  38. Svante Arrhenius first defined acids to be proton (H+) donors and bases to be hydroxide ion (OH-) donors in aqueous solution.

  39. The Arrhenius model of acids and bases is summarized by the following two reactions:

  40. Bronsted-Lowry Definition of an Acid and Base • Bronsted-Lowry Acid- a molecule or ion that is a proton donor. • Bronsted-Lowry Base- a molecule or ion that is a proton acceptor.

  41. Conjugate Acid-Base Pairs • The conjugate base of a Bronsted acid is the species that remains after an acid has donated a proton. • The conjugate acid of a Bronsted base is the species that is formed after the base has accepted the proton.

  42. Bronsted Conjugate Acid-Base Pairs

  43. The conjugate of a strong acid is a weak base.The conjugate of a strong base is a weak acid.

  44. Example of a Weak Acid Hydrofluoric Acid, HF(Hydrogen atom- Red)(Fluorine atom- Blue)

  45. Lewis Acids and Bases Lewis Acid- a molecule or ion that is an electron pair acceptor. Lewis Base- a molecule or ion that is an electron pair donor.

  46. Examples of How Bases FormBronsted Base = Proton AcceptorLewis Base = Electron Pair Donor

  47. Bases Neutralize Acids • Evergreen shrub + concrete  dead bush • Orange juice + milk  bad taste • Under a pine tree + fertilizer  white powder Acid + BaseSalt + Water • HCl + NaOHNaCl + HOH

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