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The Chemistry of Acids and Bases

The Chemistry of Acids and Bases. Some Properties of Acids. React with certain metals to produce hydrogen gas . React with carbonates and bicarbonates to produce carbon dioxide gas Taste sour Corrode metals Electrolytes React with bases to form a salt and water

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The Chemistry of Acids and Bases

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  1. The Chemistry of Acids and Bases

  2. Some Properties of Acids • React with certain metals to produce hydrogen gas. • React with carbonates and bicarbonates to produce carbon dioxide gas • Taste sour • Corrode metals • Electrolytes • React with bases to form a salt and water • pH is less than 7 • Turns blue litmus paper to red “Blue to Red”

  3. Some Properties of Bases • Taste bitter, chalky • Are electrolytes • Feel soapy, slippery • React with acids to form salts and water • pH greater than 7 • Corrosive • Turns red litmus paper to blue “Basic Blue”

  4. Acid and Bases

  5. Acid and Bases

  6. Acid and Bases

  7. Indicators • Indicators are dyes that can be added in small amounts that will change color in the presence of an acid or base. • Some indicators only work in a specific range of pH

  8. Examples: Indicators • Litmus paper • Phenolpthalein • Bromothymol blue • Methyl Orange

  9. Universal Indicator • Universal indicator is a pH indicator composed of a blend of several compounds that changes colour over a wide range of pH values from 1-14 to indicate the strength of acidity or basicity (alkalinity) of a solution. Cabbage juice pH paper

  10. A universal indicator is typically composed of water, methanol, proan-1-ol, phenolpthalein, sodium salt, methyl red, bromothylmol blue, monosodim salt and thymol blue monosodium salt.

  11. pH meter • When precise measurement of pH required. • Tests the voltage of the electrolyte • Converts the voltage to pH • Must be calibrated with a buffer solution

  12. pH of Common Substances

  13. The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion.pH = - log [H+](Remember that the [ ] mean Molarity)

  14. The pH scale is a way of expressing the strength of acids and bases. Under 7 = acid 7 = neutral Over 7 = alkaline (base)

  15. pH is a logarithmic function • pH 2 ____ more acidic than a pH of 3 • pH 2 ____ more acidic than a pH of 4 • pH 2 ____ more acidic than a pH of 5 pH = - log [H+] (Remember that the [ ] mean Molarity)

  16. Calculating the pH pH = - log [H+] (Remember that the [ ] mean Molarity) Example: If [H+] = 1 X 10-10pH = - log 1 X 10-10 pH = - (- 10) pH = 10 Example: If [H+] = 1.8 X 10-5pH = - log 1.8 X 10-5 pH = - (- 4.74) pH = 4.74

  17. Acid/Base definitions Arrhenius (Swedish chemist)

  18. Arrhenius acid is a substance that produces (dissociates – i.e. breaks down) into H+in water HCl(aq) H+ (aq) + Cl- (aq) Arrhenius base is a substance that produces (dissociated, i.e breaks down) into OH- in water NaOH (aq) ---> Na+ (aq) + OH- (aq)

  19. Strong and Weak Acids/Bases The strength of an acid (or base) is determined by the amount ofdissociation.

  20. Strong Acids • A strong acid or base is one that is completely 100% ionizes in water. Example: HCl(aq) + H2O (l) -H+ (aq) + Cl- (aq) HNO3, HCl, H2SO4 and HClO4 are among the only known strong acids. Most acids are weak.

  21. Strong Acid Dissociation(makes 100 % ions)

  22. Weak Acids • Weak acids are much less than 100% dissociated in water.

  23. Weak Acid Dissociation(only partially ionizes)

  24. Example: Weak Acid : Acetic Acid - Vinegar • CH3COOH + H2O CH3COO– + H+

  25. Strong Bases • Strong Base:100% dissociated in water. NaOH(aq) ---> Na+ (aq) + OH- (aq)

  26. Weak Bases Weak base:less than 100% ionized in water One of the best known weak bases is ammonia NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)

  27. Weak Bases

  28. Conductivity

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