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CHAPTER 13

CHAPTER 13. Acids and Bases. 13.1 The Chemical Nature of Acids and Bases. Hydrochloric acid (HCl) is a strong acid in your stomach. The acid in your stomach (HCl) can burn skin and dissolve metal!

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CHAPTER 13

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  1. CHAPTER 13 Acids and Bases 13.1 The Chemical Nature of Acids and Bases

  2. Hydrochloric acid (HCl) is a strong acid in your stomach The acid in your stomach (HCl) can burn skin and dissolve metal! A base from the pancreas (HCO3–) helps to neutralize any acid that leaves the stomach What makes an acid an acid? What makes a base a base? Bicarbonate (HCO3–) ions are produced by the pancreas

  3. From Chapter 4 Higher H+ concentration Lower H+ concentration The pH scale helps to determine whether a solution is acidic or basic.

  4. H2O(l) H+(aq) + OH–(aq) Neutral solution: Neutral solution Dissociation of water: This equilibrium lies heavily on the reactant side Only 1 out of 550 million water molecules is dissociated into a hydrogen (H+) ion In neutral water or solution, the concentrations of H+ and OH– are equal

  5. Acidic solution: Acids An acid dissolves in water to create more H+ ions than there are in neutral water

  6. Acidic solution: Acids

  7. Basic solution: Bases Sodium hydroxide (NaOH) is also known as lye or caustic soda NaOH(aq) → Na+(aq) + OH–(aq) A base dissolves in water to create more OH– ions than there are in neutral water

  8. Basic solution: Bases

  9. Bases Potassium hydroxide (KOH) is used in alkaline batteries A base dissolves in water to create more OH– ions than there are in neutral water An alkaline substance is a salt of a group 1 or group 2 metal that dissolves in water to make a base.

  10. Arrhenius theory More H+ ions More OH– ions

  11. H+ is powerful because it has no electrons! Hydronium ion (hydrated proton) The hydronium ion The whole subject of acids and bases has to do with the extraordinary chemical power of the H+ ion, the “naked proton.” When we talk about H+ in water, we’re really talking about H3O+

  12. The whole subject of acids and bases has to do with the extraordinary chemical power of the H+ ion, the “naked proton.” (aq) NH3 + H2O NH4+ + OH– Ammonia is a proton acceptor so it is a base

  13. The whole subject of acids and bases has to do with the extraordinary chemical power of the H+ ion, the “naked proton.” HNO3→H+ + NO3– (aq) Nitric acid is a proton donor It is indeed an acid

  14. Acid-base pairs A proton that is donated by one chemical (an acid) must be accepted by another chemical (a base) Acids and bases always act in pairs called conjugate acid-base pairs!

  15. Acid-base pairs

  16. Acid-base pairs NH3 is the conjugate base of NH4+ NH4+ is the conjugate acid of NH3

  17. Acid-base pairs HCl is the conjugate acid of H3O+ H3O+ is the conjugate base of HCl

  18. NH3 + H2O NH4+ + OH– H+ donor (acid) HCl + H2O H3O+ + Cl– H+ acceptor (base) Water can act as either an acid or a base! amphoteric: a substance that can act as either an acid or a base under different circumstances.

  19. HCl(aq) →H+(aq) + Cl–(aq) hydrochloric acid H2C6H6O6(aq) →2H+(aq) + C6H6O6–(aq) ascorbic acid (vitamin C) Identifying acids The H+ that gets donated is written first

  20. HCl(aq) →H+(aq) + Cl–(aq) 1 M 1 M H2C6H6O6(aq) →2H+(aq) + C6H6O6–(aq) 1 M < 0.02 M Identifying acids A strong acid dissociates completely A weak acid dissociates only partially

  21. Ca(OH)2(aq) → Ca2+(aq) + 2OH–(aq) calcium hydroxide Identifying bases The OH group at the end reminds chemists that a chemical is a base Not all bases have an OH group!

  22. Ca(OH)2(aq) → Ca2+(aq) + 2OH–(aq) 1 M 2 M KOH(aq) → K+(aq) + OH–(aq) 1 M 1 M Identifying bases A strong base dissociates completely

  23. NH3(aq) + H2O(l) NH4+(aq) + OH–(aq) 1 M ~ 0.004 M Identifying bases A weak base yields much less than 1 OH– ion per molecule of base in solution. For example, 1 mole of ammonia (NH3) produces about 0.004 moles of OH– ions.

  24. Brøndsted-Lowry: pH range: [H+] and [OH–]: Arrhenius: Acids Bases produce H+ ions in aqueous solutions produce OH– ions in aqueous solutions donate H+ ions accept H+ ions pH < 7 pH > 7 [H+] > [OH–] [H+] < [OH–] Water can act as either an acid or a base The whole subject of acids and bases has to do with the extraordinary chemical power of the H+ ion, the “naked proton”

  25. H2C6H6O6(aq) →2H+(aq) + C6H6O6–(aq) HCl(aq) →H+(aq) + Cl–(aq) 1 M < 0.02 M 1 M 1 M Strong: Complete dissociation Acids Weak: Partial dissociation

  26. H2C6H6O6(aq) →2H+(aq) + C6H6O6–(aq) HCl(aq) →H+(aq) + Cl–(aq) 1 M < 0.02 M 1 M 1 M Ca(OH)2(aq) → Ca2+(aq) + 2OH–(aq) 1 M 2 M NH3(aq) + H2O(l) NH4+(aq) + OH–(aq) 1 M ~ 0.004 M Strong: Complete dissociation Acids Weak: Partial dissociation Strong: Complete dissociation Bases Weak: Partial dissociation

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