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The Chemistry of Acids and Bases

The Chemistry of Acids and Bases. Chapter 17. Acid and Bases. Acid and Bases. Acid and Bases. Acids. Have a sour taste. Vinegar is a solution of acetic acid. Citrus fruits contain citric acid. React with certain metals to produce hydrogen gas.

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The Chemistry of Acids and Bases

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  1. The Chemistry of Acids and Bases Chapter 17

  2. Acid and Bases

  3. Acid and Bases

  4. Acid and Bases

  5. Acids Have a sour taste. Vinegar is a solution of acetic acid. Citrus fruits contain citric acid. React with certain metals to produce hydrogen gas. React with carbonates and bicarbonates to produce carbon dioxide gas Bases Have a bitter taste. Feel slippery. Many soaps contain bases.

  6. SomeProperties of Acids • Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) • 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 A-CID”

  7. Acid Nomenclature Flowchart

  8. Acid Nomenclature Review • HBr (aq) • H2CO3 • H2SO3 hydrobromicacid  carbonicacid  sulfurousacid

  9. Name ‘Em! • HI (aq) • HCl (aq) • H2SO3 • HNO3 • HIO4

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

  11. Some Common Bases NaOH sodium hydroxide lye KOH potassium hydroxide liquid soap Ba(OH)2 barium hydroxide stabilizer for plastics Mg(OH)2 magnesium hydroxide “MOM” Milk of magnesia Al(OH)3 aluminum hydroxide Maalox (antacid)

  12. Types of Acid/Base • Arrhenius (traditional) Acids – produce H+ ions (or hydronium ions H3O+) Bases – produce OH- ions (problem: some bases don’t have hydroxide ions!)

  13. Arrhenius acid is a substance that produces H+ (H3O+) in water Arrhenius base is a substance that produces OH- in water

  14. Acid/Base Type 2 • Brønsted – Lowry Acids – proton donor Bases – proton acceptor A “proton” is really just a hydrogen atom that has lost it’s electron!

  15. A Brønsted-Lowry acid is a proton donor A Brønsted-Lowry base is a proton acceptor conjugatebase conjugateacid base acid

  16. CONJUGATE ACID AND CONJUGATE BASEWHAT ARE THEY? A CONJUGATE ACID- IS THE SPECIES PRODUCED WHEN A BASE ACCEPTS A HYDROGEN ION FROM AN ACID. A CONJUGATE BASE- IS THE SPECIES THAT RESULTS WHEN AN ACID DONATES A HYDROGEN ION TO A BASE. A CONJUGATE ACID-BASE PAIR CONSISTS OF TWO SUBSTANCES RELATED TO EACH OTHER BY DONATING AND ACCEPTING OF A SINGLE HYDROGEN ION Water and other substances that can act as both acids and bases are said to be amphoteric

  17. Conjugate Pairs

  18. Monoprotic and Polyprotic Acids • Monoprotic Acid- any acid that can donate a hydrogen ion in an acid base reaction. • HCl • Polyprotic Acid- any acid that has more than one ionizable hydrogen ion and can donate them. • H2SO4

  19. Strength of Acids and Bases • Acids that ionize completely are called strong acids. HCl(aq) + H2O(l) → H3O+(aq) + Cl-(aq) • Because strong acids produce the maximum number of ions they are good conductors of electricity. • Six strongest acids: HCl HNO3 HBr HClO4 HI H2SO4

  20. Bases • Strong Bases dissociate entirely into metal ions and hydroxide ions. Also good conductors of electricity NaOH(s) → Na+(aq) + OH- (aq) • Six Strong Bases NaOH Ca(OH)2 KOH CsOH RbOH Ba(OH)2 • ****The words weak and strong refer to the degree the acid or base separates into ions.

  21. 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.Under 7 = acid 7 = neutralOver 7 = base

  22. pH of Common Substances

  23. 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

  24. Try These! Find the pH of these: 1) A 0.15 M solution of Hydrochloric acid 2) A 3.00 X 10-7 M solution of Nitric acid

  25. pOH • Since acids and bases are opposites, pH and pOH are opposites! • pOH does not really exist, but it is useful for changing bases to pH. • pOH looks at the perspective of a base pOH = - log [OH-] Since pH and pOH are on opposite ends, pH + pOH = 14

  26. [H3O+], [OH-] and pH What is the pH of the 0.0010 M NaOH solution? [OH-] = 0.0010 (or 1.0 X 10-3 M) Kw = [H3O+] [OH-] [H3O+] = 1.0 x 10-11 M pH = - log (1.0 x 10-11) = 11.00 OR pOH = - log 0.0010 pOH = 3 pH = 14 – 3 = 11

  27. pH testing • There are several ways to test pH • Blue litmus paper (red = acid) • Red litmus paper (blue = basic) • pH paper (multi-colored) • pH meter (7 is neutral, <7 acid, >7 base) • Universal indicator (multi-colored) • Indicators like phenolphthalein • Natural indicators like red cabbage, radishes

  28. Paper testing • Paper tests like litmus paper and pH paper • Put a stirring rod into the solution and stir. • Take the stirring rod out, and place a drop of the solution from the end of the stirring rod onto a piece of the paper • Read and record the color change. Note what the color indicates. • You should only use a small portion of the paper. You can use one piece of paper for several tests.

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