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Acid and Base Strength

Acid and Base Strength. 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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Acid and Base Strength

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  1. Acid and Base Strength

  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. Properties of Acids • Taste sour. • Turn litmus red. • Proton (H+) donors. • Inc. [H3O+] in aqueous solutions. • Properties of Bases • Taste bitter. • Turn litmus blue. • Proton acceptors. • Inc. [OH-] in aqueous solutions. Review

  12. pH Scale • Traditionally 0 - 14. • Can have pH < 0 or > 14. • pH < 7  Acidic solution. • pH = 7  Neutral solution. • pH > 7  Basic solution. Review

  13. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH Scale Acidic Basic pH Scale

  14. HCl, A Strong Acid

  15. HF, A Weak Acid

  16. 1x10-1 M 1x10-1 M 1x10-2 M 1x10-2 M 1x10-3 M 1x10-3 M Neutral Solution 1x10-4 M 1x10-4 M 1x10-5 M 1x10-5 M 1x10-6 M 1x10-6 M Acid added to neutral solution 1x10-7 M 1x10-7 M 1x10-8 M 1x10-8 M Base added to neutral solution 1x10-9 M 1x10-9 M 1x10-10 M 1x10-10 M 1x10-11 M 1x10-11 M 1x10-12 M 1x10-12 M 1x10-13 M 1x10-13 M As [H+] Increases, [OH-1] Decreases [OH-1] [H+]

  17. [H+] and [OH-1] in Water • In any aqueous solution: • [H+] [OH-1] = 1x10-14 • As [H+] goes up, [OH-1] must decrease. • As [OH-1] goes up, [H+] must decrease. • In other words, adding an acid to water causes the solution to become more acidic and less basic. • Adding a base to water causes the solution to become less acidic and more basic.

  18. [H+] and [OH-1] in Water • If [H+] = 1x10-3 M, what is [OH-1]? • [H+][OH-1] = 1x10-14 • (1x10-3 M)[OH-1] = 1x10-14 • [OH-1] = (1x10-14) / (1x10-3) • [OH-1] = 1x10-11 M • If [OH-1] = 1x10-8 M, what is [H+]? • [H+][OH-1] = 1x10-14 • [H+](1x10-8 M) = 1x10-14 • [H+] = (1x10-14) / (1x10-8 M) • [H+] = 1x10-6 M

  19. pH • pH = power of Hydrogen • negative logarithmic (powers of ten) scale. • pH = -log10[H+] • If [H+] = 1x10-1 M, • pH = -log(1x10-1 M) = 1 • If [H+] = 1x10-2 M, • pH = -log(1x10-2 M) = 2 • If [H+] = 1x10-3 M, • pH = -log(1x10-3 M) = 3

  20. A Few Words About Logarithms • The logarithm of a number is the power to which you would have to raise a base to equal that number. • Unless otherwise indicated, assume the base is 10. • log(100) = 2 • because 102 = 100 • log(1000) = 3 • because 103 = 1000 • log(0.001) = -3 • because 10-3 = 0.001 • log(0.000 001) = -6 • because 10-6 = 0.000 001

  21. [H3O+1] and [OH-1] [H3O+1] [OH-1]

  22. Calculations Involving pH, pOH, [H+], and [OH-] of strong Acids and Bases pH = -log [H+] pOH = -log [OH-] pOH + pH = 14

  23. pH and pOH • What are the pH values of the following solutions? • 1x10-1 M H+ • pH = -log(1x10-1 M) = 1 • 1x10-3 M H+ • pH = -log(1x10-3 M) = 3 • 1x10-5 M H+ • pH = -log(1x10-5 M) = 5 • 1x10-1 M OH-1 • [H+] = (1x10-14) / (1x10-1 M) = 1x10-13 M • pH = -log(1x10-13 M) = 13

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