CHAPTER
7
Self-Quiz
SUGGESTED ANSWERS
1.
(d); Choice (d) is correct because 6 carbon atoms 1 12 hydrogen atoms 1 6 oxygen atoms 5 total of
24 atoms. Choice (a) is incorrect because glucose has 3 different elements, not 3 atoms. Choice (b) is
incorrect because glucose has 6 carbon atoms and also 6 oxygen atoms, but those numbers are less than
the total. Choice (c) is incorrect because glucose has 12 hydrogen atoms but 24 atoms in total.
2.
(a); Choice (a) is correct because O2 represents a molecule of oxygen made up of atoms of only one
element. Choice (b) is incorrect because it represents a molecule of carbon monoxide, which contains
atoms of two elements. Choice (c) is incorrect because it represents a molecule of methane, which contains
atoms of two elements. Choice (d) is incorrect because it represents a molecule of a carbon tetrachloride,
which contains atoms of two elements.
3.
(c); In order for the ion to have a charge of −2, it must have 2 more electrons than protons (−18 1 16 5
−2). Choices (a) and (b) are incorrect because the number of electrons is less than the number of protons,
which would give the ion a positive charge. Choice (d) is incorrect because 34 is the total number of
protons and electrons, not the number of electrons.
4.
(a); Choice (a) is correct because alloys are solid solutions made up of two or more metals. Choice (b)
is incorrect because an element contains only one kind of atom. Choice (c) is incorrect because an ionic
compound is formed from a metal and a non-metal. Choice (d) is incorrect because covalent compounds
are formed from non-metals.
5.
(b); Choice (b) is correct because the formula contains atoms of only one element and more than one
atom is present. Choice (a) is incorrect because more than one atom is present. Choices (c) and (d) are
incorrect because the formula shows the presence of only one element, and it cannot be a compound.
6.
False. Diatomic molecules have two atoms in each molecule. Ozone has three oxygen atoms in each
molecule. A correct version of the statement would be: Oxygen (formula O2) is a diatomic molecule.
7.
False. Non-metals share electrons with other non-metals. A correct version of the statement would be:
Non-metals react with other non-metals to form covalent bonds.
8.
True. Toxins released in the south travel up the food chain and concentrate in the sea mammals and fish.
9.
hydrocarbons; Hydrocarbons are compounds containing only hydrogen and carbon.
10.
covalent; Carbon, hydrogen, and oxygen are all non-metals, so all the bonding is covalent.
11.
cation; A cation is an ion that has more protons than electrons. It has a positive charge. An anion has more
electrons than protons, so it as a negative charge.
12. (a)(v); (b)(i); (c)(ii); (d)(iii); (e)(iv).
13.
Their atoms have the maximum number of electrons in their outermost orbits.
14.
A compound includes atoms of different elements. Some molecules are molecular elements, which
are made up of only one kind of atom.
15. (a)
One electron was transferred from each potassium atom to a chlorine atom.
(b)
18 electrons. (217 1(21) 5 218)
(c)
18 electrons. (219 2 (21) 5 218)
NEL
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Chapter 7 Chemical Compounds
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16. (a)
(b)
Sample answer: Place one penny in salt water and compare the change in color with the one in
pure water.
(c)
Sample answer: Place one penny in vinegar and compare the change in color with the one in
pure water.
17. (a)
(b)
18. (a)
(b)
19.
Sample answer: Place one penny in water, one in a moist place, and another in a dry place. Compare
the change in color over time.
I could drop a lighted match into each flask and observe the reactions.
The match in the oxygen flask will burn brighter than it did when it was lit in the air. The match
in the carbon dioxide flask will go out right away. The match in the air flask will continue to burn
without a change in brightness.
Both metals react with oxygen in the air to form metal oxides.
The white powder is a compound of metal A and oxygen. The dark, scaly coating is a compound of
metal B and oxygen.
Sample answer: I ride to school in a car that has a steel frame. I wear jewellery made of sterling silver.
The doorknobs in my house are made of brass.
20. (a)
(b)
21. (a)
(b)
9pⴙ
10n0
4pⴙ
5n0
9pⴙ
10n0
F
Be
F
Transferring two electrons from the Be atom to the F atoms (one to each) gives all three atoms a
complete outer shell.
Oxygen reacts rapidly with wood at elevated temperatures. People are careful with campfires when
camping in the forest to prevent forest fires. They may clear the area around the campfire and make
sure to extinguish the fire completely when finished.
Oxygen reacts slowly with iron. Iron bridges are painted with rust-resistant paint to prevent the
bridges from rusting.
22.
Cl2 is covalently bonded, and NaCl is ionically bonded. Non-metals form covalent bonds with each other,
and non-metals form ionic bonds with metals.
23.
Double the number of carbon atoms and add 2; 2C 1 2 5 H. The general formula of a saturated
hydrocarbon is CnH2n12. In other words, if there are n carbon atoms in the formula, the number of
hydrogen atoms will be 2n12.
24.
carbon dioxide (CO2)
424
water (H2O)
Unit C: Atoms, Elements, and Compounds
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ammonia (NH3)
methanol (CH3OH)
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