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CHAPTER 19

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  1. CHAPTER 19 ACID, BASES & SALTS Open Textbook to page 586

  2. MANY SUBSTANCES CONTAIN ACIDS. • VINEGAR (ACETIC ACID) • CARBONATED DRINKS (PHOSPHORIC ACID) • GRAPE JUICE (TARTARIC ACID) • APPLES (MALIC ACID) • LEMONS (CITRIC ACID)

  3. MANY SUBSTANCES CONTAIN BASES. • LYE (SODIUM HYDROXIDE) FOUND IN • COMMERCIAL DRAIN CLEANERS • MILK OF MAGNESIA (MAGNESIUM HYDROXIDE) • BAKING SODA (SODIUM BICARBONATE)

  4. ACIDS: • 5 GENERAL PROPERTIES: • AQUEOUS SOLUTIONS OF ACIDS HAVE A • SOUR TASTE. • ACIDS CHANGE THE COLOR OF ACID-BASE • INDICATORS. • SOME ACIDS REACT WITH ACTIVE METALS • TO RELEASE HYDROGEN GAS. • Mg (s) + 2 HCl (aq)  MgCl2 + H2 (g)

  5. ACIDS REACT WITH BASES TO PRODUCE • SALTS AND WATER. • 5) SOME ACIDS CONDUCT ELECTRIC CURRENT.

  6. ACID NOMENCLATURE BINARY ACID: ACID THAT CONTAINS ONLY TWO DIFFERENT ELEMENTS, i.e., HYDROGEN AND ONE OF THE MORE ELECTRONEGATIVE ELEMENTS.

  7. NAMES OF BINARY ACIDS • HF HYDROFLUORIC ACID • HCl HYDROCHLORIC ACID • HBr HYDROBROMIC ACID • HI HYDROIODIC ACID • H2S HYDROSULFURIC ACID

  8. OXYACIDS ACID THAT IS A COMPOUND OF HYDROGEN, OXYGEN, AND A THIRD ELEMENT USUALLY A NONMETAL

  9. COMMON OXYACIDS • CH3COOH Acetic acid • H2CO3 Carbonic acid • HNO3 Nitric acid • H3PO4 phosphoric acid • H2SO4 sulfuric acid • H2SO3 sulfurous acid • HClO4 perchloric acid • HClO3 chloric acid • HClO2 chlorous acid • HClO hypochlorous acid

  10. Common Industrial Acids • SULFURIC ACID: MOST COMMONLY PRODUCED INDUSTRIAL CHEMICAL THE ACID USED IN AUTOMOBILE BATTERIES

  11. NITRIC ACID: • STAINS PROTEINS YELLOW • USED IN MAKING EXPLOSIVES

  12. PHOSPHORIC ACID: • USED DIRECTLY FOR MANUFACTURING • FERTILIZERS AND ANIMAL FEED. • FLAVORING AGENT IN SOFT DRINKS

  13. HYDROCHLORIC ACID: • PRODUCED BY STOMACH TO AID DIGESTION • IN HARDWARE STORES, DILUTE SOL’N KNOWN • AS MURIATIC ACID AND IS USED TO CORRECT • ACIDITY OF SWIMMING POOLS AND TO • CLEAN MASONRY.

  14. BASES5 GENERAL PROPERTIES • AQUEOUS SOLUTIONS OF BASES TASTE BITTER. • BASES CHANGE THE COLOR OF ACID-BASE INDICATORS. • DILUTE AQUEOUS SOLUTIONS OF BASES FEELS SLIPPERY.

  15. BASES5 GENERAL PROPERTIES • BASES REACT WITH ACIDS TO PRODUCE SALTS AND WATER. • BASES CONDUCT ELECTRIC CURRENT.

  16. Svante Arrhenius His theory limited because it only applies to aqueous solutions

  17. ARRENHIUS ACIDS & BASES • ARRENHIUS ACID: A CHEMICAL COMPOUND THAT INCREASES THE CONCENTRATION OF HYDROGEN IONS, H+, IN AQUEOUS SOLUTIONS

  18. ARRENHIUS ACIDS & BASES • ARRENHIUS BASE: A CHEMICAL COMPOUND THAT INCREASES THE CONCENTRATION OF HYDROXIDE IONS, OH-, IN AQUEOUS SOLUTIONS

  19. AQUEOUS SOLUTIONS OF BASES • ALKALINE • THESE BASES ARE IONIC HYDROXIDES WHICH DISSOCIATE IN SOLUTION TO RELEASEHYDROXIDE IONS. • SODIUM HYDROXIDE: NaOH NaOH (s)  Na+ (aq) + OH- (aq)

  20. Group 1 Hydroxides NaOH KOH LiOH RbOH CsOH Group 2 Hydroxides Ca(OH)2 Ba(OH)2 Sr(OH)2

  21. AnotherACID-BASE THEORIES • ARRENHIUS DEFINITION REQUIRES SUBSTANCES TO BE AQUEOUS. • DEFINITIONS REVISED TO INCLUDE SUBSTANCES THAT ACTED AS ACIDS OR BASES WHEN THEY ARE NOT IN A WATER SOLUTION.

  22. BRONSTED-LOWRY ACIDS & BASES • BRONSTED-LOWRY ACID: A MOLECULE or ION THAT IS A PROTON DONOR. • HCl + NH3 NH4+ + Cl- • HCl transfers a proton to the ammonia molecule

  23. Figure 14.3The Reaction of NH3 with HCl to Form NH4+ and Cl-

  24. BRONSTED-LOWRY BASE • MOLECULE OR ION THAT IS A PROTON ACCEPTOR.

  25. The Reaction of NH3 with HCl to Form NH4+ and Cl-AMMONIA ACCEPTS A PROTON FROM HCl thus AMMONIA IS A BRONSTED-LOWRY BASE

  26. BONSTED-LOWRY ACID-BASE REACTION • PROTONS ARE TRANSFERRED FROM ONE REACTANT (THE ACID) TO ANOTHER (THE BASE).

  27. ACID-BASE REACTIONS • BRONSTED-LOWRY ACID DONATES A H+ • SPECIES REMAINING COULD RE-ACCEPT THAT H+ AND THUS ACT AS A BASE

  28. CONJUGATE BASE • SPECIES THAT REMAINS AFTER A BRONSTED-LOWRY ACID HAS GIVEN UP A H+ ION. • HF (aq) + H2O (l)  F- (aq) + H3O+ (aq) acid conjugate base

  29. BRONSTED-LOWRY BASE ACCEPTS A H+ • SPECIES REMAINING COULD RE-DONATE THAT H+ AND THUS ACT AS AN ACID

  30. CONJUGATE ACID • SPECIES THAT FORMS AFTER A BRONSTED-LOWRY BASE HAS ACCEPTED A H+ ION. • HF (aq) + H2O (l)  F- (aq) + H3O+ (aq) base conjugate acid

  31. BRONSTED-LOWRY ACID-BASE REACTIONS Are equilibrium systems meaning that both the Forward and the reverse reactions occur. Each contain two conjugate acid-base pairs.

  32. Let’s identify the Conjugate Acid-Base Pairs HNO3 (l) + H2O (l)  H3O+ (aq) + NO3- (aq)

  33. Conjugate Acid/Base Pairs • HA(aq) + H2O(l)  H3O+(aq) + A(aq) conj conj conj conj acid 1 base 2 acid 2 base 1 DO PROBLEM 48 on page 625

  34. AMPHOTERIC COMPOUNDS • SPECIES THAT CAN ACT AS EITHER AN ACID OR A BASE H2SO4(aq) + H2O  H3O+(aq) + HSO4- (aq) base NH3 (g) + H2O (l)  NH4+(aq) + OH- (aq) acid

  35. Water as an Acid and a Base • Water is amphoteric (it can behave either as an acid or a base). • H2O (l) + H2O(l)  H3O+ + OH • conj conj • acid 1 base 2 acid 2 base 1

  36. MONOPROTIC ACIDS • ACIDS THAT CAN DONATE ONLY ONE HYDROGEN ION PER MOLECULE. • EXAMPLES HCl HNO3 HClO4

  37. Polyprotic Acids • . . . can furnish more than one Hydrogen ion (H+) to the solution. • Examples: • H2SO4 • H3PO4

  38. All polyprotic acids ionize in a stepwise Manner i.e., one HYDROGEN ION at a time. H2SO4 (l) + H2O (l)  H3O+ (aq) + HSO4- (aq) HSO4- (aq) + H2O (l)  H3O+ (aq) + SO42- (aq) Each step is weaker than the one before; therefore, concentration of ions formed in the first step is the greatest.

  39. DIPROTIC ACID: CAN DONATE TWO HYDROGEN IONS PER MOLECULES. TRIPROTIC ACID: CAN DONATE THREE HYDROGEN IONS PER MOLECULE POLYPROTIC ACIDS

  40. Lewis Acids and BasesEmphasizes role of electron pairs to form a covalent bond • Lewis Acid: electron pair acceptor • Lewis Base: electron pair donor

  41. Figure 14.12The Al(H2O)63+ ion

  42. Aluminum ion (Lewis Acid) accepts electron pairs From Water (Lewis Base) donates electron pairs to form covalent bonds. Lewis Acid-Base Reaction: formation of one or more covalent bonds between an electron-pair donor and an electron-pair acceptor.

  43. LEWIS DEFINITION BROADEST OF THE THREE ACID-BASE DEFINITIONS

  44. STRONG ACIDS • ACID THAT IONIZES COMPLETELY IN AQUEOUS SOLUTION.

  45. STRONG ACID Solutions HClO4 (aq) H2SO4 (aq) HNO3 (aq) HCl (aq) HBr (aq) HI (aq) MEMORIZE!!!

  46. WEAK ACIDS • ACID THAT IONIZES LESS THAN COMPLETELY IN AQUEOUS SOLUTION. • . Ka is the acid dissociation constant. • Smaller the Ka the weaker the acid.

  47. Figure 14.4Graphic Representation of the Behavior of Acids of Different Strengths in Aqueous Solution a) Strong Acidb) Weak Acid

  48. Figure 14.6A Strong Acid (a) and a Weak Acid (b) in Water

  49. Bases • “Strong” and “weak” are used in the same sense for bases as for acids. • strong = complete dissociation (hydroxide ion supplied to solution) • NaOH(s)  Na+(aq) + OH(aq)