3. (b) 7. (a) 26. element. 30. indicator

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1 UNIT C UnitR eview SUGGESTED ANSWERS WHAT DO YOU REMEMBER? 1. (d) 5. (c) 9. (c) 2. (a) 6. (d) 3. (b) 7. (a) 10. False. A covalent bond will form between two elements that are non-metals. 11. True 24. chemical 28. sulfur dioxide 32. physical 25. products 29. rust 33. compound 26. element 30. indicator (c) 8. (b) 12. False. The element arsenic (atomic number 33) forms an anion with an ionic charge of False. Ionic bonds result from the transfer of electrons from one element to another. 14. False. The law of conservation of mass states that the total number and type of reactant atoms and total number and type of product atoms in a chemical reaction are equal. 15. True 16. False. The products of the complete combustion of a hydrocarbon are carbon dioxide and water. 17. False. The reactants of a single displacement reaction are an element and a compound. 18. False. Dissolving sulfur dioxide gas in water produces an acidic solution. 19. False. Metals form positively charged ions by losing electrons. 20. False. Atoms of carbon dioxide are held together by covalent bonds. 21. True 22. False. When magnesium chloride (MgCl 2 ) is dissolved in water, it ionizes to form Mg 21 and Cl 2 ions. 23. True 36. K 2 1 BaCl 2 Ba 1 2 KCl 37. This is an example of a synthesis reaction. 27. noble gas 31. metals 35. hydrogen 38. Calcium oxide reacts with water to form calcium hydroxide: CaO(s) 1 H 2 O(l) Ca(OH) 2 Then, calcium hydroxide reacts with an acid, producing a salt and water. Sample equation: Ca(OH) 2 1 H 2 H 2 O(l) 1 Ca 39. (a) Because Ca is in Group 2 of the periodic table, it needs to lose two electrons to have a stable outer orbit. It becomes an ion with a 12 charge. (b) S is in Group 16 of the periodic table, which means it needs to gain two electrons to have a stable outer orbit. It becomes an ion with a 22 charge. NEL Unit Review 465

2 (c) K is in Group 1 of the period table, so it has one electron in its outermost orbit. To have a stable outer orbit, it needs to lose this electron to become an ion with a 11 charge. (d) Al is the third element in its row, which means it has three electrons in its outer orbit. It needs to lose these electrons to have a stable outer orbit, so it becomes an ion with a 13 charge. 40. Rust forms on iron as a result of synthesis reactions C 2 H O 2 4 CO H 2 O WHAT DO YOU UNDERSTAND? 42. Diagrams should show that the outer electron orbit of a phosphorus atom contains five electrons. For this outer energy level to be full (contain eight electrons), three electrons need to be added. Three added electrons give a neutral atom a charge of p 15p P P Sample answer: Ar, K 1, P (a) MgCl 2 (f) Ag 3 (b) Al 2 S 3 (g) H 2 (c) Sn (h) HCl (d) Fe 2 (i) ClO 2 (e) Pb(N ) 2 (j) N 2 O 45. (a) potassium oxide (e) nitric acid (b) copper(ii) sulfide (f) carbon monoxide (c) sodium phosphate (g) nitrogen monoxide (d) lead(ii) hydroxide 46. It tells what goes into the process and what is produced. 47. (a) synthesis (d) decomposition (b) single displacement (e) combustion (c) double displacement 48. (a) 2 NH 3 (g) 1 H 2 (NH 4 ) 2 (b) 2 Al(s) 1 3 CuCl 2 2 AlCl Cu(s) (c) H NaOH 3 H 2 O(l) 1 Na 3 (d) Al 2 ( ) 3 (s) Al 2 (s) 1 3 S (g) (e) 2 C 2 H 6 (g) 1 7 O 2 (g) 4 CO 2 (g) 1 6 H 2 O(l) 49. (a) carbon 1 iron(iii) oxide iron 1 carbon dioxide (b) 3 C(s) 1 2 Fe 2 (s) 4 Fe(l) 1 3 CO 2 (g) (c) single displacement 466 Unit C: Chemical Reactions NEL

3 50. (a) The ph would decrease. Ocean organisms that are sensitive to ph would decrease in population. (b) When these populations decrease, it also affects populations of organisms that depend on them for food. The entire ocean ecosystem is affected. 51. Sample answer: Filled outer electron orbits are very stable. A helium atom has a completely filled outer shell of two electrons. When a lithium atom loses one electron, it becomes an ion that has the same arrangement of outer electrons as helium. Left with two electrons and three protons, the lithium ion has a 11 charge. Another example is chlorine. Chlorine has seven electrons in its outermost orbit. To have a full and stable outer orbit, it must gain one electron and become an ion with a 21 charge. 2p 2n 0 3p 4n 0 17p 18n 0 He Li 52. Elements in the same group have atoms with the same number of electrons in its outer orbit. These are the electrons that are shared or transferred to form bonds. For a given element, the number of valence electrons in each atom of the element determines how many electrons will be involved in bonding, and this influences the formula of the resulting compound. Also, the bonding pattern of an element influences its chemical properties. 53. (a) potassium sulfide (e) silver nitrate (b) carbon tetrabromide (c) iron(ii) oxide (d) copper(ii) sulfate FeCl 3 1 SnCl 2 2 FeCl 2 1 SnCl 4 SOLVE A PROBLEM (f) lead dioxide (g) nitrous oxide 55. (a) It is likely to be a metal. It is shiny and silver-coloured, and is a good conductor of electricity. (b) XO (c) An acid such as HCl can neutralize the solution. 56. The mass of oxygen consumed in the reaction is 43 g. 57. (a) The state symbol (l) indicates a single substance that is a liquid. The state symbol indicates that the chemical is dissolved in water and is present as a solution. (b) Bubbles of hydrogen gas would form. (c) The bubbles would stop forming. (d) The mass would stay the same, as explained by the law of conservation of mass. The atoms that are in the reactants are identical to the atoms present in the products. (e) The resulting solution is basic, so the phenolphthalein turns pink. 58. Sample answer: Immediately, my family can reduce our use of electricity and use alternate forms of transportation. In the long term, we can support legislation to control emissions by corporations g of CO 2 was produced. Cl NEL Unit Review 467

4 60. XH 3. Each Mg atom would lose its two outer electrons so that its outer orbit would be a full and stable orbit. Because each Mg ion has a charge of 12, three Mg ions would have a total charge of 16. To balance this charge, the two ions of X would each have to have a charge of 23. Because X has a charge of 23, three hydrogen atoms would be needed to balance it. CREATE AND EVALUATE 61. Sample answers: (a) Burning of fossil fuels releases sulfur dioxide and nitrogen oxides into the environment. These pollutants combine with water in the air to form sulfuric acid and nitric acid, which then come down in the form of acid precipitation. An increase in the number of cars means more fossil fuels are being burned and more sulfur oxides are produced, which in turn increase the level of acid precipitation. (b) To minimize the acid-causing emissions from cars, the new town could build an efficient mass transit system and also build bike lanes around the city. This would reduce the number of people that would otherwise drive a car. The city could also implement a carpooling system to further reduce the number of cars on the road. Lastly, there could be some sort of incentive, such as a rebate, for people who participated in these programs. 62. Sample answers: (a) I would design a community to have efficient public transportation. There would also be bike lanes to encourage bicyclists. I would also support legislation and enforcement of pollution-control laws. (b) Whereas my community has public buses, there are not a lot of bike lanes. Laws concerning pollutioncontrol are not always enforced. 63. In both instances, indicator shows an organism or substance that changes if its surrounding environment changes. 64. Sample answers: (a) As a result of acid precipitation, forests produce less oxygen and use less carbon dioxide. This means fewer products made from forest resources, such as lumber, and they are more expensive. (b) lumber, paper (c) My family and I could use public transportation instead of driving. We could also reduce the amount of electricity we use. 65. More people in one car results in fewer cars on the road. Fewer cars means reduced acid-causing emissions. 66. Mining and refining metals cause pollutants to be released into the air that lead to acid precipitation. An economic slowdown that results in less demand for metals mined in Ontario may lead to a decrease in acid precipitation, because reduced mining will lead to fewer acid precipitation-causing pollutants. 67. (a) CO is produced by incomplete combustion of fossil fuels in faulty furnaces or poorly maintained vehicle engines. CO 2 is produced by the combustion of fossil fuels in an adequate air supply, as in the case of many power sources. (b) CO is a poisonous gas that can cause death if inhaled. Carbon dioxide is a greenhouse gas and is considered one of the major causes of climate change. (c) The amount of CO released by a vehicle engine can be reduced by better engine maintenance or engine overhaul. CO 2 emissions can be reduced by carpooling and by converting to energy sources that do not rely on burning fossil fuels, such as wind and solar power. REFLECT ON YOUR LEARNING 68. Sample answer: I now know that some things I poured down the drain might be strongly acidic or basic, which can affect the ph of water and soil, and consequently, entire ecosystems. What affected me the most was finding out how many household products can do that. If I know something is basic or acidic, I will now neutralize it with baking soda or vinegar before pouring it down the drain. 468 Unit C: Chemical Reactions NEL

5 69. Sample answer: I used to think that air pollution was produced mainly by factory smoke stacks. I learned that air pollutants are produced by several other sources as well. For example, automobile exhaust contains nitrogen oxides, which become a part of smog. Also, the combustion of hydrocarbon fuels produces carbon dioxide, a greenhouse gas, and incomplete combustion produces soot and carbon monoxide. WEB CONNECTIONS 70. Research, evaluations, and recommendations should be fair and unbiased. Any testing should identify variables. Any recommendation should be justified by accurate scientific reasoning. 71. Both sides of the issue should be presented in a fair and unbiased manner. For example, if a student chooses Are biofuels the solution to our future energy needs? as their issue, the environmental view could include the idea that biofuels might increase the amount of carbon dioxide in the atmosphere. Using biofuels also reduces the number of growing plant matter, which decreases the amount of oxygen produced and the amount of carbon dioxide removed from the atmosphere. An economic view could show that using biofuels could be more economical than using fossil fuels. 72. Be sure that students investigate the more recent decisions. Students will probably find that target dates have been extended because of a lack of alternative fuels. NEL Unit Review 469