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 Have a bitter taste. Feel slippery. Many soaps contain bases. Bases

3 ACIDS An acid is a compound that increases the number of hydrogen ions when dissolved in water (H+) (present as H 3 O + 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 þ Produce H + (as H 3 O + ) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) þ Taste sour þ Corrode metals þ Electrolytes þ React with bases to form a salt and water þ pH is less than 7 þ 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 Nomenclature Review No Oxygen  w/Oxygen An easy way to remember which goes with which… “In the cafeteria, you ATE something ICky”

8 Acid Nomenclature Flowchart

9 HBr (aq)HBr (aq) H 2 CO 3H 2 CO 3 H 2 SO 3H 2 SO 3  hydrobromic acid  carbonic acid  sulfurous acid Acid Nomenclature Review

10 Acid and Bases

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13 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”

14 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

15 Some Common Bases NaOHsodium hydroxidelye KOHpotassium hydroxideliquid soap Ba(OH) 2 barium hydroxidestabilizer for plastics Mg(OH) 2 magnesium hydroxide“MOM” Milk of magnesia Al(OH) 3 aluminum hydroxideMaalox (antacid) Al(OH) 3 aluminum hydroxideMaalox (antacid)

16 Acid/Base definitions Definition #1: Arrhenius (traditional) Acids – produce H + ions (or hydronium ions H 3 O + ) Bases – produce OH - ions (problem: some bases don’t have hydroxide ions!)

17 Arrhenius acid is a substance that produces H + (H 3 O + ) in water Arrhenius base is a substance that produces OH - in water

A CID B ASE NEUTRALNEUTRAL The pH Scale Acid and Base strength is measured on a scale that ranges from 0 to 14. Let’s get pHunky!

19 The pH scale is a way of expressing the strength of acids and bases. Under 7 = acid 7 = neutral Over 7 = base Note: Stronger acids have lower numbers & stronger bases have higher numbers

20 What does “pH” mean? pH stands for “power of hydronium ion”

21 pH of Common Substances

22 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.

23 INDICATORS Litmus paper is an indicator  An acid turns blue litmus paper red  A base turns red litmus paper blue Cabbage juice can be used as an indicator

24 pH testing There are several ways to test pHThere 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 base) –Universal indicator (multi-colored) –Indicators like phenolphthalein –Natural indicators like red cabbage, radishes

25 Paper testing Paper tests like litmus paper and pH paperPaper 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.

26 pH meter Tests the voltage of the electrolyteTests the voltage of the electrolyte Converts the voltage to pHConverts the voltage to pH Very cheap, accurateVery cheap, accurate Must be calibrated with a buffer solutionMust be calibrated with a buffer solution

27 pH indicators Indicators are dyes that can be added that will change color in the presence of an acid or base. Some indicators only work in a specific range of pH Once the drops are added, the sample is ruined Some dyes are natural, like radish skin or red cabbage

28 Neutralization Reaction When an acid and a base are combined a salt and water are formed. Ex. HCl + NaOH → NaCl + H 2 O (acid) (base) (salt) (water) The pH of the salt should be close to neutral (pH 7)