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1 Learning Checkpoint, p A solution with a ph of 11 is basic. 2. A solution with a ph of 5 is acidic. 3. The ph of pure water is 7 (neutral).! "#$%&'$!()! *+&$(,)#$! 4. No, litmus paper does not determine a specific ph value. It only indicates whether the solution is acidic or basic. 5. A universal indicator allows you to determine a specific ph value. Learning Checkpoint, p (a) Hydrochloric acid (b) Nitric acid (c) Acetic (or ethanoic) acid 2. (a) The polyatomic ion is sulphate. (b) The polyatomic ion is nitrate.! "#$%&'$!()! *+&$(,)#$! Learning Checkpoint, p (a) Potassium hydroxide (b) Calcium hydroxide (c) Magnesium hydroxide (d) Ammonium hydroxide! "#$%&'$!()! *+&$(,)#$! 2. Hydroxide (the OH ) is the polyatomic group that is found at the end of the chemical formula for most bases.

2 !"#$ Key Concept Review 1. An acid is a substance that produces a solution with a ph less than 7. Several types of acids are citric acid, ascorbic acid (vitamin C), hydrochloric acid, lactic acid, and sulphuric acid. 2. A base is a substance that produces a solution with a ph greater than 7. Two examples of bases are sodium hydroxide and ammonium hydroxide (see Table 5.6, student book page 201). 3. (a) The solution is basic. (b) The solution is acidic. (c) The solution is acidic. (d) The solution is acidic. (e) The solution is basic. 4. A solution that contains dissolved calcium hydroxide, Ca(OH 2 ), would be basic because bases include the hydroxide (OH ) ion. 5. Acids are similar to bases in that they dissolve in water, conduct electricity in aqueous solution, and can irritate or burn skin. Acids are different from bases in that acids taste sour (while bases taste bitter), have a ph less than 7 (while bases have a ph greater than 7), turn blue litmus paper red (whereas bases turn red litmus paper blue), and corrode metals (bases do not corrode metals). 6. An acid-base indicator is any substance that changes colour in the presence of an acid or a base. 7. (a) KOH(aq) is basic. (b) Al(OH) 3 (aq) is basic. (c) HCl(aq) is an acid. (d) C 6 H 5 COOH(aq) is an acid. 8. (a) HNO 3 (aq) (b) CsOH (c) HCl(aq) (d) H 3 PO 4 (aq) (e) potassium hydroxide (f) sulphuric acid or aqueous hydrogen sulphate 9. (a) Mg(OH) 2 (b) KOH (c) Al(OH) 3

3 11. For litmus paper, BLUE + Acid RED. Therefore, the upper of the two strips in the photograph was dipped into the lemon juice. The lower of the two strips was dipped into the solution of baking soda and water. 12. We cannot use 100% acetic acid on foods because the acid would be so concentrated that it would burn the tongue, mouth, and digestive system. 13. Litmus paper provides only a narrow range of colours to indicate ph (typically pink and blue) and is capable of indicating only if a solution is acidic or basic. A universal indicator is more useful than litmus paper because it indicates specific ph values. 14. Students will use the information in this section (and possibly their own additional ideas) to construct and complete a chart. Uses for Acids DNA passes on genetic characteristics. Hydrochloric acid in the stomach digests food. Vinegar is used as an ingredient to flavour food. To conduct electricity in car batteries To etch glass To produce dyes for clothing Students may include information from Table 5.4, student book page 200. Uses for Bases Soaps and cleaners Making plastic and textiles Making glass, cement, and steel Treating indigestion Students may include other uses from Table 5.6, student book page 201.

4 Answers to Practice Problems 5.1, p HBr(aq) + KOH(aq) KBr(aq) + H 2 O(l). 2. H 2 SO 4 (aq) + Mg(OH) 2 (aq) MgSO 4 (aq) + 2H 2 O(l). 3. H 3 PO 4 (aq) + 3NaOH(aq) Na 3 PO 4 (aq) + 3H 2 O(l). Learning Checkpoint, p. 209! "#$%&'$!()! *+&$(,)#$! 1. Sulphur oxides (SO 2 and SO 3 ) and nitrogen oxides (NOx) are the main gases that cause acid precipitation. NOx refers to the fact that there are several different gases made of nitrogen and oxygen. 2. Nitrogen oxides are gases composed of nitrogen atom(s) and one or more oxygen atoms. Examples are NO 2, N 2 O, and N 2 O Two chemical equations for reactions that cause acid precipitation are: 2SO 2 (g) + O 2 (g) 2SO 3 (g) SO 3 (g) + H 2 O(l) H 2 SO 4 (aq) 4. The source of water is water vapour in the air. Students might also name the source as rain or water evaporated from Earth s surface. 5. Students answers will vary but will include two of the following industries or human activities that contribute to acid precipitation: coal-fired power plants, iron and steel production, smelting of metals (such as zinc, nickel, and copper), fertilizer production, pulp and paper production, and automobile emissions.

5 Learning Checkpoint, p. 210! "#$%&'$!()! *+&$(,)#$! 1. Two effects that acid precipitation has on the environment are that lakes become more acidic, affecting organisms that live in the water, and acid precipitation changes the ph of the soil, which can cause trees and other plant species to die. 2. The ph of an acidic lake can be increased by adding bases such as lime (Ca(OH) 2 ) to the source of the lake or directly to the lake itself. 3. Lakes on limestone rock are less affected by acid rain because the limestone rock neutralizes the acid in the rain that falls on the lake or enters the lake through rivers. 4. Scrubbers are devices found in smokestacks of industries such as coal-fired power plants and ore-smelting facilities that release sulphur dioxide gas and nitrogen oxide gases. Scrubbers, a specially formulated chemical mixture, remove these gases by reacting with the emissions. 5. The chemical equation for the reaction in catalytic converters is: 2N 2 O 3 (g) 2N 2 (g) + 3O 2 (g).

6 !"#$ Key Concept Review 1. Neutralization is a chemical reaction between an acid and a base that produces water (H 2 O) and a salt. 2. The products of a neutralization reaction are a salt (an ionic compound) and water. 3. Antacids are composed of bases, which undergo a neutralization reaction with some of the hydrochloric acid in the stomach. This makes the stomach contents less acidic and less painful. 4. Acid precipitation is rain, snow, fog, or dew that has a ph less than Two gases that contribute to acid precipitation are sulphur dioxide (SO 2 ) (and also SO 3 ), and nitrogen oxides (NOx). NOx refers to the fact that there are several different gases made of nitrogen and oxygen. 6. Acid leaching is a process in which acids (from acid precipitation or contaminated groundwater) dissolve metals found in soil. For example, mine tailings that produce iron sulphide can produce sulphuric acid when exposed to air and water. This acid solution can enter the water system and dissolve heavy metals in the soil. Once they are released, they can contaminate the water supply. Connect Your Understanding 7. Chemical reaction (b) is a neutralization reaction because the reactants include an acid (H 3 PO 4 ) and a base (NaOH) and because the products are a salt (Na 3 PO 4 ) and water (H 2 O). 8. The completed word equations are: (a) sulphuric acid + calcium hydroxide water + calcium sulphate (b) hydrogen bromide + sodium hydroxide water + sodium bromide (c) hydrochloric acid + sodium hydroxide water + sodium chloride 9. The skeleton equations for the neutralization reactions in question 8 are: (a) H 2 SO 4 + Ca(OH) 2 H 2 O + CaSO 4 (b) HBr + NaOH H 2 O + NaBr (c) HCl + NaOH H 2 O + NaCl

7 10. The balanced chemical equations for the neutralization reactions in question 8 are: (a) H 2 SO 4 + Ca(OH) 2 2H 2 O + CaSO 4 (b) HBr + NaOH H 2 O + NaBr (same as the skeleton equation) (c) HCl + NaOH H 2 O + NaCl (same as the skeleton equation) 11. The classmate s conclusion is incorrect because the products of a neutralization reaction are water and a salt. If the salt dissolved, the solution would be clear. An example would be chemical reaction (c) in question 8. A chemical reaction has happened, but there is no visible evidence of it. 12. Two or more reasons to avoid using an antacid regularly are that long-term use of an antacid might have side effects that could affect your health, and long-term use could mask a more serious problem in the digestive system. Students may find this question challenging. 13. Acid rain can be a problem anywhere metals are used out of doors, such as in support reinforcing bars for concrete roads, cars and structures (buildings and bridges), and public artwork (statues). The acids react with the metals and corrode them. Also, if precipitation is acidic enough, it may cause acid leaching of metals into the soil, which can contaminate water supplies. 14. Acid rain is a costly result of human activities because we constantly need to monitor and replace metals, stone, and concrete used in building and roads. The damaged statue in the photograph is an illustration of the harmful effects of acid precipitation. The statue cannot be repaired, so if acid rain continues, the statue, a cultural artefact, will be lost forever. 15. Acid precipitation affects the water in lakes by making the lake water more acidic. The lowering of the ph can cause fish and other water organisms to die. Acidic lakes also cannot support the same variety of organisms as healthy lakes. 16. If a lake has formed on limestone, the limestone can protect the lake from acidification by neutralizing excess acid in the lake s water. 17. A negative effect of acid leaching is the acid leaching of heavy metals from soil in areas surrounding abandoned mine sites. The acid and metals can reach water systems, and both the metals and the acids can harm organisms. On the other hand, soils contaminated by heavy metals can be cleaned of contaminants by using acid leaching to remove them.

8 !" Key Concept Review 1. The following Venn diagram shows the similarities and differences between acids and bases. Students may choose another graphic organizer. 2. Litmus paper is blue or red litmus dried onto strips of paper. Red litmus paper turns blue when it is dipped into a basic solution. Blue litmus paper turns red when it is dipped in an acidic solution. 3. The ph scale is a number scale that can be used to classify solutions as acidic, basic, or neutral. Any substance in an aqueous solution with a ph of 7 is neutral. An acid is a substance that produces a solution with a ph less than 7. A base is a substance that produces a solution with a ph greater than (a) This solution is acidic. (b) This solution is neutral. (c) This solution is neutral. (d) This solution is basic. (e) This solution is basic.

9 Connect Your Understanding 5. The normal ph of blood is slightly basic. We know this because ph values for basic solutions are greater than You could safely test the liquid to determine if it is an acid (or a base) by using litmus paper, ph paper, or universal indicator solution. 7. Since each step on the ph scale represents a tenfold change in concentration, the first solution is 10! 10 = 100 times more concentrated, thus 100 times more acidic, than the second solution. 8. The girl appears to find the lemon sour. Sourness is a property of acids, so the lemon is probably acidic.

10 9. (a) H 2 SO 4 (aq) is an acid because it starts with hydrogen. (b) CH 3 COOH(aq) is an acid because it ends with COOH (carboxyl polyatomic group). (c) Mg(OH) 2 (aq) is a base because it contains the OH ion. 10. (a) H 2 SO 4 (aq); acid (b) Ca(OH) 2 (aq); base (c) HBr(aq); acid (d) magnesium hydroxide solution: Mg(OH) 2 (aq); base 11. (a) hydrofluoric acid (aqueous hydrogen fluoride); acid (b) nitric acid (aqueous hydrogen nitrate); acid (c) sodium hydroxide; base (d) ammonium hydroxide; base (e) acetic acid (ethanoic acid); acid (f) phosphoric acid (aqueous hydrogen phosphate); acid (g) calcium hydroxide; base 12. Two ways that human activities could disrupt the normal ph of bodies of water and cause harm to fish are acid precipitation, caused by emissions from coal-fired power plants and other industries and by automobile emissions, and acid leaching from mine tailings (waste rock). Both of these lower the ph in bodies of water. If the ph is low enough, it will harm or even kill fish. 13. (a) Hydrochloric acid (HCl) is an acid. Sodium hydroxide, NaOH, is a base. As NaOH is added to the beaker, the ph reading on the meter will rise. (b) As the base is added to the acid, it enters into a neutralization reaction with the acid, which makes the solution less acidic, so the ph rises. 14. (a) Your body can get rid of excess acids by converting them into less harmful substances or by producing bases to neutralize them. They could also excrete them in their urine. (b) A lab technician could test a urine sample to determine its ph using ph paper, a ph meter, or universal indicator. (Note that litmus paper is not a good answer here as it does not provide the actual ph of a solution.) 15. (a) Teeth are strongly susceptible to attack by acids, and basic saliva prevents acids from damaging them. Saliva can help to neutralize acids in the food we eat, such as those in lemons. (b) Drinking a lot of acidic soft drinks will expose your teeth to excess amounts of acid. Eventually the acids will corrode the tooth enamel, which will lead to cavities.

11 16. Student answers will vary but may include some of the following positive aspects of being an environmental chemist: gaining a greater understanding of the acids, bases, and chemical processes in nature; assisting in the remediation of polluted areas in the environment; researching ways to decrease pollution; and studying the effects of chemicals on plants and animals to gain a greater understanding of its effects on humans. 17. Students will select one of the acids or bases in this chapter and use it to write a story in the first person using facts from this chapter and information gained through Internet or library research. 18. Students will select one of the acids and one of the bases in this chapter and write a dialogue between them using facts from this chapter and information gained through Internet or library research. 19. Students will design a visual device to remember the differences between acids and bases (one such device is provided earlier on page 197). 20. (a) Coal-fired plants can release sulphur oxide gases (SO 2 and SO 3 ) and nitrogen oxide (NOx) gases into the atmosphere. These combine with water vapour to produce sulphuric acid (H 2 SO 4 (aq)) and nitric acid (HNO 3 (aq)) (b) Scrubbers are devices that are found in tall industrial smokestacks of industries, such as coal-fuelled power plants and ore smelting facilities, that release sulphur dioxide gas and nitrogen oxide gases. A specially formulated chemical mixture in the scrubber combines with these gases in chemical reactions, and the products of the reaction can be removed and recycled.