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chapter22Acids, Bases, and Salts1section Acids and BasesWhat You’ll Learnhow acids and bases aresimilar and different formulas and uses ofcommon acids andbases Before You ReadThink of a food or drink you like that tastes sour. What doyou think gives it a sour taste?Read to LearnA Compare and Contrast Make the following Foldableto help you understand acidsand 4CHAPTER 22 Acids, Bases, and SaltsAcidsWhat do you think about when you hear the word acid?Do you think of a substance that can burn your skin or put ahole in metal? Many sour foods contain acids. Some acids aredangerous to handle. Others are safe, and some are good to eat.What are the properties of acids?An acid is a substance that produces hydrogen ions, H , ina water solution. When an acid dissolves in water, some ofthe hydrogen atoms are released as hydrogen ions, H . It isthe ability to produce these H ions that gives acids theircharacteristic properties. When an acid dissolves in water, H ions interact with water molecules to form hydronium ions.A hydronium ion (hi DROH nee um I ahn), H3O , is acombination of an H ion and a water molecule.Acids have some common properties. All acids taste sour.But you should never taste a substance to see if it is acidic.Some acids can burn you. Acids are corrosive, which meansthey seem to eat away some metals. When an acid reacts witha metal, hydrogen gas and metallic compounds form. Acidsalso cause indicators to change color. An indicator is anorganic compound that changes color in acid and base.Litmus paper is an indicator that turns red in acids.What are some common acids?Many foods contain acids. Citrus fruits contain citric acid.Lactic acid is found in yogurt and buttermilk. Pickled foodscontain vinegar, also known as acetic acid. Your stomach useshydrochloric acid to help it digest food.Copyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Underline As you read,underline any words orsentences you think might beimportant to remember. Whenyou finish reading, look back atwhat you underlined to makesure you understand it.

Copyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Common Acids and Their UsesName, FormulaUse (example)Other InformationAcetic acid, CH3COOHFood preservationand preparationWhen in solution with water,it is known as vinegar.Acetylsalicylic acid,HOOC–C6H4–OOCCH3Pain relief, fever relief,inflammation reductionKnown as aspirinAscorbic acid, H2C6H6O6Antioxidant, vitaminCalled vitamin CCarbonic acid, H2CO3Carbonated drinksInvolved in cave, stalactite, andstalagmite formation and acid rainHydrochloric acid, HClDigestion as gastric juice instomach, to clean steel in aprocess called picklingCommonly called muriatic acidNitric acid, HNO3To make fertilizersColorless, yet yellows whenexposed to lightPhosphoric acid, H3PO4To make detergents,fertilizers and soft drinksSlightly sour but pleasant taste,detergents containing phosphatescause water pollutionSulfuric acid, H2SO4Car batteries, to manufacturefertilizers and other chemicalsDehydrating agent, causes burns byremoving water from cellsSome common acids and their uses are listed in the table.Many of these acids are important in making products, suchas fertilizer. Remember that many acids can burn your skin.BasesA base is any substance that forms hydroxide ions, OH–, ina water solution. A base is also any substance that accepts H ions from acids.Unlike acids, not many foods are bases. Egg whites andbaking powder are two foods that are basic. Some medicines,such as antacids, are basic. A common base is soap. Acharacteristic of bases is that they feel slippery, like soapy water.Many cleaning products contain bases. Bases are important inindustry, also. For example, sodium hydroxide is a base that isused to separate cellulose fibers from wood pulp to make paper.Picture This1. Identify Look at the acidslisted in the table above.What is the first element inthe chemical formula ofmost acids?Reading Essentials395

What are the properties of bases?Picture This2. Identify Look at the baseslisted in the table. Whatmolecule do most of thebases have in theirchemical formulas?Bases are the opposites of acids. While bases and acids doshare some features, bases also have their own properties.When they are not dissolved in water, many bases are solids inthe form of crystals. In solution, bases feel slippery and tastebitter. Like strong acids, strong bases are corrosive. Bases canburn you. Never taste or touch a substance to see if it is basic.Bases also cause indicators to change color. Litmus paper is anindicator that turns blue in bases.What are some common bases?The table below lists some common bases and their uses.You may have used many common bases found in cleaningproducts and not even known it.Name, FormulaUsesOther InformationAluminumhydroxide,Al(OH)3Color-fast fabrics,antacid, waterpurificationSticky gel that collectssuspended clay and dirtparticles on its surfaceCalcium hydroxide, Leather-making,Ca(OH)2mortar and plaster,lessen acidity of soilCalled caustic limeLaxative, antacidMagnesiumhydroxide, Mg(OH)2Called milk of magnesiawhen in waterCalled lye and caustic soda;Sodium hydroxide, To make soap, ovencleaner, drain cleaner, generates heat (exothermic)NaOHtextiles, and paperwhen combined with water,reacts with metals to formhydrogenAmmonia, NH33. Explain Why is water themain solvent for acidic andbasic solutions?Cleaners, fertilizer, to Irritating odor that ismake rayon and nylon damaging to nasalpassages and lungsSolutions of Acids and BasesMany products that contain acids and bases are solutions.Water is the main solvent for these solutions because watermolecules have polarity. Remember, polarity means amolecule has a slight positive charge on one end and a slightnegative charge on the other end.396CHAPTER 22 Acids, Bases, and SaltsCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Common Bases and Their Uses

What happens when acids dissolve in water?Remember that an acid produces hydrogen ions (H ) inwater. When an acid dissolves in water, the negative ends ofnearby water molecules attract the positive hydrogen in theacid. The acid separates into ions, which is called dissociation.What is left after dissociation are negative ions and positiveH ions. The H ions combine with water molecules to formhydronium ions (H3O ). Therefore, an acid compoundproduces hydronium ions when dissolved in water. The figureshows the dissociation of hydrogen chloride (HCl) intohydronium and chloride ions.H HClHClH HOOH ClHH3O H2OPicture This4. Identify When HCldissociates, what ionsdoes it produce?Cl What happens when bases dissolve in water?Copyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Bases form hydroxide ions (OH–) in water. In the table ofbases on the previous page, you can see that most bases have–OH in their formulas. When bases dissolve in water, thepositive ends of nearby water molecules attract the OH– ions inthe base. The base dissociates. What is left after dissociation arepositive ions and negative OH– ions. Unlike acid dissociation,the OH– ions do not combine with water molecules. The figureshows the dissociation of sodium hydroxide (NaOH).NaOH H2ONa OH H2O NaONaOHH HONaOH2ONa OHOH HOOPicture This5. Identify When NaOHdissociates, it produces amolecule of water, H20and two ions. What ionsdoes it produce?H2OHow is ammonia different from other bases?Ammonia, NH3, is a base that does not contain –OH. Inwater, ammonia actually dissociates water molecules. Anammonia molecule attracts a hydrogen ion from a water molecule to form an ammonium ion, NH4 . The rest of the watermolecule is a hydroxide ion, OH–. Ammonia is found in manyhousehold cleaners. You should never use products containingammonia with other cleaners that contain chlorine (sodiumhypochlorite), such as bathroom bowl cleaners and bleach.Ammonia reacts with sodium hypochlorite and produces toxicgases that can severely damage lung tissue and cause death.Reading Essentials397

After You ReadMini Glossaryacid: a substance that produces hydrogen ions, H , in ahydronium ion: a combination of a water molecule and awater solutionbase: any substance that forms hydroxide ions, OH–, in a watersolution or a substance that accepts H ions from acidshydrogen ionhydroxide ion: OH– ion formed when bases dissolve in waterindicator: an organic compound that changes color in acidand base1. Review the terms and their definitions in the Mini Glossary. Write a sentence using theterm for the substance that makes many foods taste sour.2. Fill in the Venn diagram with properties of acids and bases. Be sure to put any propertiesthat acids and bases have in common in the part where the ovals overlap. Formin water Taste Turn litmusBasesions Cause Formions in water Taste Turn litmus Feel3.You underlined words and sentences in this section that you thought wouldbe important to remember. How did this help you learn about the topics in the section?End ofSection398CHAPTER 22 Acids, Bases, and SaltsCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Acids

acid. The acid separates into ions, which is called dissociation. What is left after dissociation are negative ions and positive H ions. The H ions combine with water molecules to form hydronium ions (H 3O ). Therefore, an acid compound produces hydronium ions when dissolved in water. The figure shows the dissociation of