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ACIDS AND BASES Name some acids and bases that are familiar to you. 2

WHAT ARE SOME PROPERTIES OF ACIDS? Taste sour Turn litmus paper red Conduct electricity Very corrosive to metals React with metals Acids react with bases to produce salts and water Litmus Paper Zinc reacting with hydrochloric acid 3

WHAT ARE SOME PROPERTIES OF BASES? Taste bitter Turn litmus paper blue Conduct electricity Very corrosive Feel slippery Bases react with acids to produce salts and water 4

WHAT ARE SOME EXAMPLES OF ACIDS? Acetic acid is found in vinegar Ascorbic acid is found in citrus fruits Hydrochloric acid is found in your stomach Phosphoric acid is found in fertilizers and the soft drinks you drink Nitric acid is used in some explosives like TNT 5

WHAT ARE SOME EXAMPLES OF BASES? Ammonia (NH 3 ) is often found in cleaning products Potassium hydroxide (KOH) has many uses in industry, and can be a precursor to making soaps Sodium bicarbonate (NaHCO 3 ) is found in baking soda Calcium carbonate (CaCO 3 ) is found in antacids Sodium hydroxide (NaOH) is found in lye KOH in pure form Antacids neutralize stomach acids 6

WHAT EXAMPLES OF ACIDS AND BASES MIGHT YOU HAVE AROUND YOUR HOUSE? Acids ? Bases ? 7 Vitamin C Folic Acid Lemons Limes Oranges Grapes Vinegar Tomatoes Baking Soda Drain cleaner Window cleaner Floor cleaner Soaps Detergents Bleach Antacids

THE STRENGTH OF ACIDS A strong acid ionizes, or dissociates, completely in aqueous solutions to form H 3 O + (or H + ). A strong acid is a strong electrolyte – it conducts electricity easily. A weak acid will not ionize completely in aqueous solutions. A weak acid will be a weak electrolyte. Sulfuric acid is a strong acid. Phosphoric acid is a weak acid. 8

THE STRENGTH OF BASES Strong bases completely dissociate into its ions (OH - ) in aqueous solutions. Strong bases are strong electrolytes. Not all bases are ionic compounds – ammonia (NH 3 ) is molecular. Sodium hydroxide is a strong base. Ammonia is a weak base. 9

MEASURING THE STRENGTH OF ACIDS AND BASES The amount of hydronium (H + ) ions and hydroxide (OH - ) ions in solution can be detected by various chemicals or an electronic device, called a pH meter. A pH meter measures the pH value of a substance. pH Scale The measured pH value will be a number between 0 and 14 on a pH Scale. This is a value that reflects the negative of the common logarithm of the ion concentration. 10

THE PH SCALE 014 Increasing Acidity Increasing Basicity NeutralNeutral 7 pH stands for the French words pouvoir hydrogene, meaning the power of Hydrogen. 11

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ANOTHER WAY TO VIEW THE CHANGING AMOUNTS OF H + AND OH - IONS Low pH = Acid = High amount of H + ion, low amount of OH - ion High pH = Base = Low amount of H + ion, high amount of OH - ion 13

THE PH SCALE Stronger Acid Stronger Base NeutralNeutral 14 A substance with a pH of 4 is more acidic than a substance with a pH of 5. A substance with a pH of 11 is a stronger base than a substance with a pH of 8.5.

MEASURING THE STRENGTH OF ACIDS AND BASES Acid-base indicators are liquid chemicals which will change color in the presence of these ions. Some acid-base indicators are: phenolphthalein, methyl red, bromthymol blue, phenol red, methyl orange, red wine, cabbage juice, and beet juice. Liquid acid-base indicators will give you an approximate pH value. 15

MEASURING THE STRENGTH OF ACIDS AND BASES Litmus paper will also give an approximate value of pH. Some litmus paper only indicates if it’s an acid or a base, not its strength or its pH. Some litmus paper indicates approximate pH values, thus approximate strength. 16

NEUTRALIZATION REACTIONS Acids and bases of equivalent strength, when added together, will form salts and water. This is neutralization. Example: HCl(aq) + NaOH(aq) NaCl(aq) + H 2 O(l) NaCl is salt H 2 O is water. This is a neutralization reaction – the pH will be 7. 17

NEUTRALIZATION REACTIONS A strong acid can neutralize a strong base. A weak acid can neutralize a weak base. But… If we add 100ml of a strong acid to 50 ml of a strong base, the result will be a weaker acid, and not necessarily a neutral solution. 18

NEUTRALIZATION Antacids relieve indigestion, usually caused by excess stomach acid. But, taking an antacid, which is a weak base, will react with the strong acid in the stomach to produce a weaker acid, and thus the person will feel better. 19

REVIEW – TRUE/FALSE 20

TRUE or FALSE? 1. ACIDS DISSOCIATE IN WATER TO FORM H 3 O - IONS. 21

TRUE or FALSE? 2. ACIDS TASTE BITTER AND BASES TASTE SOUR. 22

ACIDS TASTE SOUR, AND BASES TASTE BITTER. 23

TRUE or FALSE? 3. A STRONG ACID IS A STRONG ELECTROLYTE. 24

TRUE or FALSE? 4. AMMONIA (PH 10)IS A STRONGER BASE THAN ANTACID (PH 8). 25

TRUE or FALSE? 5. THE PH SCALE MEASURES VALUES FROM 0-14, WITH 7 BEING NEUTRAL. 26

TRUE or FALSE? 6. PH STANDS FOR THE POWER OF HYDROXIDE. 27

PH STANDS FOR THE POWER OF HYDROGEN. 28

TRUE or FALSE? 7. BASES PRODUCE HYDROXIDE IONS IN AQUEOUS SOLUTIONS. 29

TRUE or FALSE? 8. LIQUID PH INDICATORS GIVE EXACT PH VALUES. 30

LIQUID PH INDICATORS GIVE APPROXIMATE PH VALUES. 31

TRUE or FALSE? 9. ADDING ACIDS AND BASES TOGETHER ALWAYS RESULTS IN A NEUTRAL SOLUTION. 32

ADDING ACIDS AND BASES TOGETHER CAN PRODUCE A NEUTRAL SOLUTION BUT ONLY IF THEY ARE OF EQUIVALENT STRENGTHS AND AMOUNTS. 33