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Acids and Bases: Definitions, Properties, and Reactions

Learn about the definitions, properties, and reactions of acids and bases, including neutralization reactions and the pH scale.

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Acids and Bases: Definitions, Properties, and Reactions

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  1. Chemistry Chapter 15 Acids and Bases

  2. Some Definitions • Arrhenius acids and bases • Acid: Substance that, when dissolved in water, increases the concentration of hydrogen/hydronium ions (protons, H+ orH3O+). • Base: Substance that, when dissolved in water, increases the concentration of hydroxide ions.

  3. Some Definitions • Brønsted–Lowry: must have both 1. an Acid: Proton donor and 2. a Base: Proton acceptor

  4. Brønsted-Lowry acids and bases are always paired. The Brønsted-Lowry acid donates a proton, while the Brønsted-Lowry base accepts it. Which is the acid and which is the base in each of these rxns?

  5. What Happens When an Acid Dissolves in Water? • Water acts as a Brønsted–Lowry base and abstracts a proton (H+) from the acid. • As a result, a hydronium ion (H3O+) is formed.

  6. Ionization of HCl and formation of hydronium ion, H3O+ H2O + HCl  H3O+ + Cl- Proton acceptor Proton donor

  7. A Brønsted–Lowry acid… …must have a removable (acidic) proton. HCl, H2O, H2SO4 A Brønsted–Lowry base… …must have a pair of nonbonding electrons. NH3, H2O

  8. Salts • Compounds that dissociate releasing neither H+ or OH- ions • Example: KCl K+ + Cl-

  9. Properties of Acids • Acids taste sour • Acids affect 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 • Acids are electrolytes • Acids neutralize bases to produce a salt and water

  10. Acids change Indicators Blue litmus paper turns red in contact with an acid.

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

  12. Acids Neutralize Bases HCl + NaOH  NaCl + H2O Neutralization reactions ALWAYS produce a salt and water.

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

  14. H3PO4 - soft drinks, fertilizer, detergents H2SO4 - fertilizer, car batteries HCl - gastric juice HC2H3O2 - vinegar Uses ACIDS

  15. Acids you must know: Strong Acids Weak Acids Sulfuric acid, H2SO4 Phosphoric acid, H3PO4 Hydrochloric acid, HCl Acetic acid, HC2H3O2 Nitric acid, HNO3 Hydrobromic acid, HBr Hydroiodic acid, HI Perchloric acid, HClO4

  16. Properties of Bases • Bases taste bitter • Bases affect 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 to produce a salt and water

  17. Examples of Bases • Sodium hydroxide (lye), NaOH • Potassium hydroxide, KOH • Magnesium hydroxide, Mg(OH)2 • Calcium hydroxide (lime), Ca(OH)2

  18. NaOH - lye, drain and oven cleaner Mg(OH)2 - laxative, antacid NH3 - cleaners, fertilizer Uses BASES

  19. Naming Acids, Bases, Salts • Bases & Salts- Ionic • Name the same as ionic compounds • Acids • Binary • 2 elements, first hydrogen • Hydro___ic acid • Ternary • 3 elements, change ending • -ate  ic, -ite  ous

  20. Strong Acids vs. Weak Acids Strong acids are assumed to be 100% ionized in solution (good proton donors). HCl H2SO4 HNO3 Weak acids are usually less than 5% ionized in solution (poor proton donors). H3PO4 HC2H3O2 Organic acids

  21. Strong Acid Dissociation

  22. Weak Acid Dissociation

  23. Concept Test • Which of the following "molecular" pictures best represents a concentrated solution of the weak acid HA? A B

  24. 14 0 7 INCREASING BASICITY INCREASING ACIDITY NEUTRAL pH Scale • pH • a measure of the concentration of H3O+ ions in solution • measured with a pH meter or an indicator with a wide color range

  25. Acids Have a pH less than 7

  26. Bases have a pH greater than 7

  27. pH Scale pH of Common Substances

  28. = Neutralization Reaction ACID + BASE  SALT + WATER HCl + NaOH  NaCl + H2O Neutralization does not always mean pH = 7.

  29. KOH + HNO3 H2O + KNO3 Neutralization Reaction Acid? Base? Salt? HNO3 KOH KNO3

  30. Products of Neutralization HCl + NaOH  NaCl + H2O H2SO4 + Ca(OH)2 CaSO4 + 2 H2O HNO3 + KOH  KNO3 + H2O The products of neutralization are always a ______ and _______. salt water

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