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Acids, Bases, and pH

Acids, Bases, and pH. Properties of acids. 1. Sour taste. 2. Contain hydrogen, react with active metals to give off H 2 gas. 3. Change the color of indicators. 4. React with bases to produce salts and water e.g. 2NaOH + H 2 SO 4 → 2H 2 O + Na 2 SO 4.

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Acids, Bases, and pH

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  1. Acids, Bases, and pH

  2. Properties of acids 1. Sour taste

  3. 2. Contain hydrogen, react with active metals to give off H2 gas

  4. 3. Change the color of indicators

  5. 4. React with bases to produce salts and water e.g. 2NaOH + H2SO4 → 2H2O + Na2SO4

  6. 5. Acids are electrolytes

  7. Traditional definition of an acid • A cmpd. That contains hydrogen and ionizes in aqueous soln. to form hydrogen ions (H+)

  8. Common acids • HCl – hydrochloric acid • H2SO4 – sulfuric acid • HC2H3O2 – acetic acid • HNO3 – nitric acid • H3PO4 – phosphoric acid

  9. Sulfuric acid • #1 industrial chemical • Fertilizers, petroleum refining, …… • Used as a measure of a country’s economy

  10. Acetic acid • Dilute acetic acid is vinegar

  11. Acid Precipitation • Combustion of fossil fuels • Is the main cause of acid precipitation

  12. 4.6 4.3 4.6 4.3 4.6 4.1 4.3 4.6 Europe North America

  13. Bases

  14. Properties of bases 1. Bitter taste

  15. 2. Feel slippery to the skin 3. Change color of indicators

  16. 4. React with acids to produce water and salts e.g. 2NaOH + H2SO4 → 2H2O + Na2SO4 5. Bases are electrolytes

  17. Traditional definition of a base • OH- producer

  18. Neutralization reactions • Reaction of hydronium ions (H3O+) and hydroxide (OH-) ions to form water H3O+ +OH- 2H2O HCl + NaOH  H2O + NaCl (NaCl is a salt)

  19. Common bases

  20. Sodium hydroxide • (NaOH), also known as lye or caustic soda, is a caustic metallic base. It is widely used in many industries, mostly as a strong chemicalbase in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents. Worldwide production in 1998 was around 45 million tons.

  21. pH scale

  22. pH • - log [H+] • e.g. if [H+] = 1 x 10-8M pH = 8

  23. If [H+] = 3.4 x 10-5 find pH = -[(log 3.4 + log 10-5)] = -[(0.53) + (-5)] = -(0.53 – 5) = 4.47

  24. If the pH is 2 what is the [H+] pH = -log [H+] log [H+] = -pH [H+] = antilog (-pH) = antilog (-2) = 1 x 10-2 M

  25. If the pH is 6.4 what is [H+] [H+] = antilog (-pH) = antilog (-6.4) = 4.0 x 10-7M

  26. If the pH is 5.4 what is [H+] [H+] = antilog (-pH) = antilog (-5.4) = 4.0 x 10-6 M

  27. [H+] [OH-] = 1 x 10-14 • Therefore if [OH-] = 1 x 10-10 pH = 4 • if [OH-] = 1 x 10-7 pH = 7

  28. Diprotic acid • Can donate (2) protons (H+) per molecule • e.g. H2SO4

  29. Triprotic • Donates (3) protons • e.g. H3PO4

  30. Normality (N ) = (molarity) x (whole # factor) # equivalents solute / L of solution

  31. What is the normality of a soln w/ 1 mol H2SO4 dissolved in 1 L of soln? 2 equivalents x 1 mol H2SO4 = 2 equivalents 1 mol H2SO4 1 L 1 L = 2 N H2SO4

  32. Titration • Controlled addition & measurement of amt. of soln. of a known conc. That is required to react completely with a measured amt. of soln. of unknown conc.

  33. Graph of titration results

  34. Saponification • hydrolysis of an ester under basic conditions to form an alcohol and the salt of a carboxylic acid. Saponification is commonly used to refer to the reaction of a metallic alkali (base) with a fat or oil to form soap.

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