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Acid-Base theories

Acid-Base theories. An Introduction. Properties of acids and bases. Acids: Taste sour or tart React with some metals to produce H 2 ( g ) Turn litmus paper red Can be strong (HCl) or weak (CH 3 COOH). Properties of acids and bases. Common Acids: HCl: hydrochloric acid

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Acid-Base theories

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  1. Acid-Base theories • An Introduction

  2. Properties of acids and bases • Acids: • Taste sour or tart • React with some metals to produce H2(g) • Turn litmus paper red • Can be strong (HCl) or weak (CH3COOH)

  3. Properties of acids and bases • Common Acids: • HCl: hydrochloric acid • HNO3: nitric acid • H2SO4: sulfuric acid • H3PO4: phosphoric acid • CH3COOH: acetic (ethanoic) acid • H2CO3: carbonic acid

  4. Properties of acids and bases • Bases: • Taste bitter • Feel slippery • Turn litmus paper blue • Can be strong (NaOH) or weak (NH3)

  5. Properties of acids and bases • Common Bases: • KOH: potassium hydroxide • NaOH: sodium hydroxide • Ca(OH)2: calcium hydroxide • Mg(OH)2: magnesium hydroxide

  6. Theories • Acid-Base theories try to explain the actions of acids and bases. • Acids and bases play such a very important role in general and biochemistry that we need a good theory to help us understand the reactions. • In addition, with a good theory, we should be able to predict the products of unknown but related reactions.

  7. Theories • All theories deal with strong and weak acids and bases. • Strong acids and bases are fully dissociated in solution. • HCl(g) → H+(aq) + Cl-(aq) • NaOH(s) → Na+(aq) + OH-(aq) • The reactions go to completion. • There are no reactants present in the solution.

  8. Theories • Strong acids (these are all of them): • HCl hydrochloric acid • HBr hydrobromic acid • HI hydroiodic acid • HNO3 nitric acid • HClO3 chloric acid • H2SO4 sulfuric acid

  9. Theories • Strong bases: • all metal hydroxides, such as • NaOH sodium hydroxide • KOH potassium hydroxide • Ca(OH)2 calcium hydroxide

  10. Theories • Weak acids and bases are only partially dissociated. • There is an equilibrium when the rate of product formation equals the rate of reactant formation. • CH3COOH(aq) + H2O(l) ⇌ H3O+(aq) + CH3COO-(aq) • NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq) • Both reactants and products remain in solution.

  11. Theories • Weak acids: • any acid not a strong acid, such as • H3PO4 phosphoric acid • CH3COOH acetic acid • HF hydrofluoric acid

  12. Theories • Weak bases: • any base that is not a metal hydroxide, such as • NH3 ammonia • CH3NH2 methylamine • CH3CH2NH2 ethylamine • and other nitrogen containing organic compounds

  13. Arrhenius acids and bases • Arrhenius acids are • H+ containing compounds • increase the H+ concentration in water • Typical reactions: • H-Cl(g) → H+(aq) + Cl-(aq) • H-Cl(g) + H2O(l)→ H3O+(aq) + Cl-(aq) hydronium ion

  14. Arrhenius acids and bases • Arrhenius bases are • OH- containing compounds • increase the OH- concentration in water • Typical Reactions: • NaOH(s) → Na+(aq) + OH-(aq) • KOH(s) → K+(aq) + OH-(aq)

  15. Brønsted-Lowry acids and bases • Brønsted-Lowry acids are • H+ donors • HCl(g) + H2O(l) → Cl-(aq) + H3O+(aq) • Brønsted-Lowry bases are • H+ acceptors • NH3(g) + H2O(l) → NH4+(aq) + OH-(aq)

  16. Brønsted-Lowry acids and bases • Conjugate acids and bases: • HCl(g) + H2O(l) → Cl-(aq) + H3O+(aq) • In this reaction • HCl is the H+ donor (acid) • H2O is the H+ acceptor (base) (acid) (base)

  17. Brønsted-Lowry acids and bases • Conjugate acids and bases: • HCl(g) + H2O(l) → Cl-(aq) + H3O+(aq) • In the reverse reaction (acid) (base) (base) (acid) • H3O+ is the H+ donor (acid) • Cl- is the H+ acceptor (base)

  18. Brønsted-Lowry acids and bases • Conjugate acids and bases: • HCl(g) + H2O(l) → Cl-(aq) + H3O+(aq) (acid) (base) (base) (acid) • HCl is an acid • Cl- is a base • HCl and Cl- are conjugate acid and base.

  19. Brønsted-Lowry acids and bases • Conjugate acids and bases: • HCl(g) + H2O(l) → Cl-(aq) + H3O+(aq) (acid) (base) (base) (acid) • H3O+ is an acid • H2O is a base • H3O+ and H2O are conjugate acid and base.

  20. Brønsted-Lowry acids and bases • Conjugate acids and bases: • NH3(g) + H2O(l) → NH4+(aq) + OH-(aq) • In this reaction • H2O is the H+ donor (acid) • NH3 is the H+ acceptor (base) (base) (acid)

  21. Brønsted-Lowry acids and bases • Conjugate acids and bases: • NH3(g) + H2O(l) → NH4+(aq) + OH-(aq) • In the reverse reaction (base) (acid) (acid) (base) • NH4+ is the H+ donor (acid) • OH- is the H+ acceptor (base)

  22. Brønsted-Lowry acids and bases • Conjugate acids and bases: • NH3(g) + H2O(l) → NH4+(aq) + OH-(aq) (base) (acid) (acid) (base) • NH3 is a base • NH4+ is an acid • NH3 and NH4+ are conjugate acid and base.

  23. Brønsted-Lowry acids and bases • Conjugate acids and bases: • NH3(g) + H2O(l) → NH4+(aq) + OH-(aq) (base) (acid) (acid) (base) • H2O is an acid • OH- is a base • H2O and OH- are conjugate acid and base.

  24. Brønsted-Lowry acids and bases • Notice that in the reaction • HCl(g) + H2O(l) → Cl-(aq) + H3O+(aq) • H2O acts as a base • and in the reaction • NH3(g) + H2O(l) → NH4+(aq) + OH-(aq) • H2O acts as an acid

  25. Brønsted-Lowry acids and bases • The behavior of water to act as a base or as an acid is called amphoterism. • Water is amphoteric. • Other species can also be amphoteric: • HSO4- (hydrogen sulfate ion) • HCO3- (hydrogen carbonate ion) • H2PO4- (dihydrogen phosphate ion)

  26. . . • : • . . Lewis acids and bases • Lewis acid: • e- pair acceptor • H+ (the H is e- poor) • Lewis base: • e- pair donor • O−H- (the O is e- rich)

  27. Lewis acids and bases • Lewis acid/base reactions: • H+(aq) + H2O(l) → H3O+(aq) • H3O+ is called a Lewis acid/base adduct. • NH3(g) + H+(aq) → NH4+(aq) • Cl3B(g) + :NH3(g) → Cl3B−NH3(s) • Cl3B−NH3 is called a Lewis acid/base adduct.

  28. acids/bases theories

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