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Acids and Bases Part 1

Acids and Bases Part 1. Jackson Bettis Michael Martzahn. Definitions. Acids are H + donors. They give up H + ions (protons) Bases are H + acceptors. They are compounds that snatch up H + ions. Conjugate Acids donate protons in the forward chemical reaction

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Acids and Bases Part 1

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  1. Acids and Bases Part 1 Jackson Bettis Michael Martzahn

  2. Definitions • Acids are H+ donors. They give up H+ ions (protons) • Bases are H+ acceptors. They are compounds that snatch up H+ ions. • Conjugate Acids donate protons in the forward chemical reaction • Conjugate Bases accept protons in the forward chemical reaction

  3. Identification • Acids have an H in front usually • Acids have a pH of less than 7 • Bases have an OH sometimes • Bases have a pH of more than 7 • Conjugate Bases of strong acids are terrible bases that have no effect on pH • Conjugate Bases of weak acids are weak bases and thus do affect pH

  4. Identification, cont. • Conjugate acids of weak bases are weak acids and do affect pH

  5. What it means to be a strong acid • Strong Acids dissociate completely in water • Therefore, they give up more protons than weak acids

  6. The Six Strong Acids • HCl • HNO3 • H2SO4 • HClO4 • HI • HBr

  7. Acid dissociation reaction in water • H2O <-> H+ + OH- • Therefore, water can act as a base or an acid

  8. Kw • Kw = 1.0 * 10-14 • Kw / [OH-] = [H+] • Kw / [H+] = [OH-] • -log[H+] = pH • -log[OH-] = pOH • pH + pOH = 14

  9. Writing Ka expressions • Ka = [H+][A-] / [HA] • Kb = [OH-][HB+] / [B] • Ka * Kb = Kw

  10. Calculating pH • For strong acids: -log[H+] • For strong bases: -log[OH-] • For weak acids or bases: ICE table

  11. Calculating pH, cont. • 1.) determine major species in solution • 2.) Decide which species in the reaction will control [H+] • 3.) Set up an ICE table for the reaction to determine [H+]

  12. Calculating pH of buffers • Ex.) We add 0.05 mols of NaOH to a 500 mL solution of 0.25 M HOCl and 0.20 M NaOCl. Assume no volume change.

  13. Sample problem :D • Calculate the pH of a 0.20 M solution of HF (Ka = 7.2 * 10-4)

  14. Another Sample Problem • 20. The ionization constant for acetic acid is 1.8 × 10–5; that for hydrocyanic acid is 4 × 10–10. In 0.1 M solutions of sodium acetate and sodium cyanide, it is true that • (a) [H+] equals [OH–] in each solution • (b) [H+] exceeds [OH–] in each solution • (c) [H+] of the sodium acetate solution is less than that of the sodium cyanide solution • (d) [OH–] of the sodium acetate solution is less than that of the sodium cyanide solution • (e) [OH–] for the two solutions is the same

  15. Yet another sample problem • 12. A solution prepared by mixing 10 mL of 1 M HCl and 10 mL of 1.2 M NaOH has a pH of • (a) 0 • (b) 1 • (c) 7 • (d) 13 • (e) 14

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