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Accelerated Chemistry I Wednesday, April 9, 2008

Accelerated Chemistry I Wednesday, April 9, 2008. Today’s Topic: Equilibrium Lab Equilibrium Discussion HW: Equilibrium Idea/Acids and Bases II Lab Reports: Due Today. Trivia Tuesday.

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Accelerated Chemistry I Wednesday, April 9, 2008

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  1. Accelerated Chemistry I Wednesday, April 9, 2008 • Today’s Topic: • Equilibrium Lab • Equilibrium Discussion • HW: Equilibrium Idea/Acids and Bases II • Lab Reports: Due Today

  2. Trivia Tuesday Step off Canada's Mount Thor and you'll fall 4,100 feet — more than three-quarters of a mile — straight down. It's the world's largest vertical drop.

  3. Some Definitions • Arrhenius • Acid: Substance that, when dissolved in water, increases the concentration of hydrogen ions. • Base: Substance that, when dissolved in water, increases the concentration of hydroxide ions.

  4. Some Definitions • Brønsted–Lowry • Acid: Proton donor • Base: Proton acceptor

  5. A Brønsted–Lowry acid… …must have a removable (acidic) proton. A Brønsted–Lowry base… …must have a pair of nonbonding electrons.

  6. If it can be either… ...it is amphiprotic. HCO3− HSO4− H2O

  7. Both substances act as Brønsted-Lowry bases. • Neither substance acts as a Brønsted-Lowry base. • NH3(aq) • HSO4–(aq)

  8. Both substances act as Brønsted-Lowry bases. • Neither substance acts as a Brønsted-Lowry base. • NH3(aq) • HSO4–(aq)

  9. 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, the conjugate base of the acid and a hydronium ion are formed.

  10. Conjugate Acids and Bases: • From the Latin word conjugare, meaning “to join together.” • Reactions between acids and bases always yield their conjugate bases and acids.

  11. Acid and Base Strength • Strong acids are completely dissociated in water. • Their conjugate bases are quite weak. • Weak acids only dissociate partially in water. • Their conjugate bases are weak bases.

  12. Acid and Base Strength • Substances with negligible acidity do not dissociate in water. • Their conjugate bases are exceedingly strong.

  13. Acid and Base Strength In any acid-base reaction, the equilibrium will favor the reaction that moves the proton to the stronger base. HCl(aq) + H2O(l) H3O+(aq) + Cl−(aq) H2O is a much stronger base than Cl−, so the equilibrium lies so far to the right K is not measured (K>>1).

  14. C2H3O2(aq) + H2O(l) H3O+(aq) + C2H3O2−(aq) Acid and Base Strength Acetate is a stronger base than H2O, so the equilibrium favors the left side (K<1).

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