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Acids and Bases

Acids and Bases. Acids. Have a sour taste. Acids. Turn blue litmus red. Turn methyl orange red. Acids. Will react with: some metals to produce a salt and H 2 . metal oxides to produce a salt and H 2 O. metal carbonates to produce a salt, H 2 O, and CO 2.

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Acids and Bases

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  1. Acids and Bases

  2. Acids • Have a sour taste.

  3. Acids • Turn blue litmus red. • Turn methyl orange red.

  4. Acids • Will react with: • some metals to produce a salt and H2. • metal oxides to produce a salt and H2O. • metal carbonates to produce a salt, H2O, and CO2. • bases to produce a salt and H2O. • Mg + 2HCl  MgCl2 + H2 • MgO + 2HCl  MgCl2 + H2O • MgCO3 + 2HCl  MgCl2 + H2O + CO2 • Mg(OH)2 + 2HCl  MgCl2 + 2H2O

  5. Acids • Are electrolytes. • Conduct an electric current when dissolved.

  6. Bases • Have a bitter taste. Coffee itself is acidic, but it contains an alkaline compound – caffeine – which contributes to its bitter taste.

  7. Bases • Feel slimy or slippery to the touch.

  8. Bases • Turn red litmus blue. • Turn methyl orange yellow. • Turn phenolphthalein pink. Litmus pH scale.

  9. Bases • React with acids to produce salt and H2O. • HCl + NaOH  NaCl + H2O

  10. Bases • Are electrolytes.

  11. Definitions of Acids and Bases • Arrhenius Definition • Acids increase [H3O+1] (hydronium ion concentration) in aqueous solutions. • HCl(aq) + H2O(l) Cl-1(aq) + H3O+1(aq) • Bases increase [OH-1] ions in aqueous solutions. • NaOH(s)  Na+1(aq) + OH-1(aq)

  12. H Hydrogen ion (proton) Acid + Hydronium ion, H3O+1 H - H H H H H H H H H H H H H H H H H H H H H H H H H H + H - Hydrogen and Hydronium Ions

  13. Hydroxide ion, OH-1 Base H + H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H Hydroxide Ions

  14. Definitions of Acids and Bases • Bronsted-Lowry Definition • Most commonly used definition. • Acids are proton (H+1 ion) donors. • Allows water-insoluble substances to be acids, as long as they can give up H+1 ions. • Bases are proton acceptors.

  15. proton (H+ ion) Bronsted-Lowry Definition • HCl + NH3 NH4+1 + Cl-1 - + +

  16. Conjugate Acid-Base Pairs • When a B-L acid loses a proton, it becomes a relative (or conjugate) base. • HF + H2O  F-1 + H3O+1 • F-1 + H2O  HF + OH-1 • An acid and its conjugate base are called a conjugate acid/base pair.

  17. Some Conj. Acid-Base Pairs Acid Conjugate Base Reaction HCl Cl-1 HCl  H+1 + Cl-1 H2SO4 HSO4-1 H2SO4 H+1 + HSO4-1 NH4+1 NH3 NH4+1 H+1 + NH3 H3O+1 H2O H3O+1 H+1 + H2O H2O OH-1 H2O  H+1 + OH-1

  18. Some Conj. Acid-Base Pairs Base Conjugate Acid Reaction OH-1 H2O OH-1 + H+1 H2O H2O H3O+1 H2O + H+1  H3O+1 NH3 NH4+1 NH3 + H+1  NH4+1 CO3-2 HCO3-1 CO3-2 + H+1 HCO3-1 HPO4-2 H2PO4-1 HPO4-2 + H+1 H2PO4-1

  19. Acids and Bases • Identify the acid, base, conjugate acid, and conjugate base in each of the following reactions: • HCl + NH3 Cl-1 + NH4+1 • Acid: HCl • Base: NH3 • Conjugate acid: NH4+1 • Conjugate base: Cl-1 • H2O + HF  H3O+1 + F-1 • Acid: HF • Base: H2O • Conjugate acid: H3O+1 • Conjugate base: F-1

  20. Amphoteric Substances • Amphoteric = capable of acting as an acid or a base. • Example: H2O • H2O + F-1 OH-1 + HF • H2O + HF  H3O+ + F- • Example: HSO4-1 • HSO4-1 + OH-1 SO4-2 + H2O • HSO4-1 + H3O+1  H2SO4 + H2O

  21. Definitions of Acids and Bases • Lewis definition • An acid is an electron-pair acceptor. • A base is an electron-pair donor. • Explains why Al+3 and Fe+3 ions are acidic although they have no H+1 ions to give up. • Lewis acids are e- deficient: • Metal cations, BF3 • Lewis bases have lone pairs of e-. • NH3, H2O, Cl-1, etc.

  22. F F H H N F F B B C H H H F F H H N C H H H A Lewis Acid-Base Reaction

  23. - - - - Cl Cl Cl Cl Cl Cl Cl Co Cl Another Example -2 Co2+

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