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The Chemistry of Acids and Bases

The Chemistry of Acids and Bases. Chemistry I – Chapter 19 Chemistry I HD – Chapter 16 ICP – Chapter 23.

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The Chemistry of Acids and Bases

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  1. The Chemistry of Acids and Bases Chemistry I – Chapter 19 Chemistry I HD – Chapter 16 ICP – Chapter 23 SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNcheck "Background Printing")!

  2. 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.

  3. ACIDS • An acid is a compound that increases the number of hydrogen ions when dissolved in water (H+) (present as H3O+ ions) • An acid solution tastes sour • An acid can change the color of certain compounds

  4. What is an ion? An ion is an atom that has lost or gained an electron giving it a positive (+) or negative (-) charge.

  5. Some Properties 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”

  6. USES OF ACIDS • Citric acid and ascorbic acid (Vitamin C) are found in orange juice • Carbonic acid and phosphoric acid give a “bite” to soft drinks • Acids in your stomach aid in digestion • Sulfuric acid is the most widely used industrial acid in the world. It is used in making metals, paper, paints, and fertilizers.

  7. Acid and Bases

  8. Acid and Bases

  9. Acid and Bases

  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. Uses of Bases • Bases are used in soaps (remember, bases are slippery) • Bases are used to make paper, in oven cleaners, and to unclog drains • Ammonia is a base and is used in many household cleaners

  12. 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)

  13. Acid/Base definitions Acids – produce H+ ions (or hydronium ions H3O+) Bases – produce OH- ions (problem: some bases don’t have hydroxide ions!)

  14. Most acids produce H+ (H3O+) in water Some bases produce OH- in water

  15. NEUTRAL The pH Scale ACID BASE 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Let’s get pHunky! Acid and Base strength is measured ona scale that ranges from 0 to 14.

  16. The pH scale is a way of expressing the strength of acids and bases. Under 7 = acid 7 = neutralOver 7 = baseNote: Stronger acids have lower numbers & stronger bases have higher numbers

  17. What does “pH” mean? • pH stands for “power of hydronium ion”

  18. Detecting Acids and Bases • You can detect an acid using an indicator. • INDICATOR - A substance that changes color in the presence of an acid or a base.

  19. INDICATORS • Litmus paper is an indicator • An acid turns blue litmus paper red • A base turns red litmus paperblue • Cabbage juice can be used as an indicator

  20. 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

  21. 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.

  22. pH meter • Tests the voltage of the electrolyte • Converts the voltage to pH • Very cheap, accurate • Must be calibrated with a buffer solution

  23. Neutralization Reaction • When an acid and a base are combined a salt and water are formed. • Ex. HCl + NaOH → NaCl + H2O (acid) (base) (salt) (water) The pH of the salt should be close to neutral (pH 7)

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