Chapter 9 Acids and Bases

Vocabulary Acid—a hydrogen containing compound that ionizes in water to produce hydrogen ions and is a proton donor Base—a hydroxide containing compound that ionizes in water to produce hydroxide ions and is a proton acceptor. Indicator—compounds that show a definite color change when mixed with an acid or base.

Emulsify—dissolves fats and oils Electrolytes—a substance whose water solution conducts an electric current. Emulsify—dissolves fats and oils Salt—compound formed from the positive ion of a base and the negative ion of an acid. The compound is neutral. Neutralization—the name of a reaction between an acid and a base. Insoluble—will not dissolve in water.

Acids and Bases Around Us Acids and bases are all around us every day. Acids are in aspirin, vitamin C, oranges, grapes, lemons, grapefruit, apples, milk, tea, pickles, vinegar, and carbonated beverages Bases are in lye, milk of magnesia, deodorant, ammonia, and soaps. Acid is necessary for digestion and bases, such as antacids help when our stomach hurts. Industry depends on acids and bases as well. Metals are cleaned with acids. Bases are used for making fertilizer and synthetic fibers. Both are used to make medicine.

Turn to your partner and name two common things in which you find acids and two common things in which you find bases.

Properties of Acids Acids taste sour. Acids affect the color of indicators Litmus paper changes from blue to red. Acids react with metals for form H2 and a metal compound. The acid corrodes the metal and produces a residue. All acids contain hydrogen, but not everything that contains hydrogen is an acid. When an acid is mixed with water, acids ionize to produce hydrogen ions (H+). This ion is rapidly surrounded by water to form a hydronium ion H3O.

Common Acids Strong Acids Weak Acids Sulfuric Acid—H2SO4 Nitric Acid—HNO3 Hydrochloric Acid—HCl Strong acids are good electrolytes. Weak Acids Acetic Acid—HC2H3O2 Carbonic Acid H2CO3 Boric Acid—H3BO3 Weak acids are poor electrolytes.

Properties of Bases Bases taste bitter. Bases are slippery to the touch. Bases turn litmus paper from red to blue. Bases emulsify All bases contain the hydroxide ion (OH-). When dissolved in water, bases produce this ion. Because the hydroxide ion can combine with the hydrogen ion and form water, bases are referred to as proton acceptors.

Common Bases Strong Bases Weak Bases Strong bases are good electrolytes. Potassium hydroxide—KOH Sodium hydroxide—NaOH Calcium hydroxide—Ca(OH)2 Weak Bases Weak bases are poor electrolytes. Ammonium hydroxide—NH4OH Aluminum hydroxide—Al(OH)3

Turn to your partner and list two characteristics of an acid and a base. Then try to name one acid and one base.

Acids and Bases in Solution: Salts To measure the acidity of a solution, the pH scale is used. This measures the concentration of H3O (hydronium). pH is a scale from 0 – 14. Seven is neutral; 0 – 6 is acidic; 8 – 14 is basic. Strong acids have low pH values. Strong bases have high pH values.

Determining pH pH is determined by using an indicator. Litmus Phenolphthalein pH paper Methyl orange Bromthymol blue Red cabbage juice Grape juice

Incidator Acid Base Litmus paper Red Blue Colorless Pink Red to pink Phenolphthalein Colorless Pink pH paper Red to pink Blue to green Methyl orange Yellow Bromthymol blue Red cabbage Grape juice

Formation of Salts When acids react chemically with bases they form salts. The process is called neutralization. The reaction produces a salt and water. Many of the salts formed are insoluble. The insoluble substance that crystallizes is called a precipitate because they fall out of the solution. Example: HCl + NaOH  H2O + NaCl

Exercise your brain!!! Write the chemical equation to demonstrate the neutralization of sulfuric acid and sodium hydroxide. Here is a hint: Sulfuric acid is H2SO4 Sodium hydroxide is NaOH When you think you have it, come write it on the board 