Section 5.3: Elements and Their Oxides
Section 5.3 Questions, page 204
1. Answers may vary: Sample answer:
2. The addition of a small quantity of an acid to a basic solution would lower the pH of the
solution because the acid would neutralize some of the base.
3. (a) Barium oxide will form a basic solution with water.
(b) Potassium oxide will form a basic solution with water.
(c) Chlorine dioxide will form an acidic solution with water.
(d) Arsenic trioxide will form an acidic solution with water.
4. (a) 4 K(s) + O2(g) → 2 K2O(s)
2 K2O(s) + H2O(l) → 2 KOH(aq)
(b) 2 Cl2(g) + O2(g) → 2 Cl2O(g)
Cl2O(g) + H2O(l) → 2 HClO(aq)
(c) P4(s) + 5 O2(g) → 2 P2O5(s)
P2O5(s) + 3 H2O(l) → 2 H3PO4(aq)
5. The chemical equation for the reaction is: K2O(s) + H2O(l) → 2 KOH(aq)
Potassium oxide reacts with water to form potassium hydroxide, which is a base. Therefore, the
pH of the solution rises to 10.
6. Calcium oxide forms a basic solution when mixed with water. Since basic solutions can be
corrosive, it is important to avoid skin contact when mixing cement.
7. Passing the nitrogen oxide emissions through a catalytic converter is more sustainable than
passing the emissions through a mixture of calcium oxide and water. This process does not use
up any other chemicals and catalysts can be reused continuously.
8. Sulfur oxides like sulfur dioxide are common in the gases emitted by volcanoes. Sulfur
dioxide forms an acidic solution when it reacts with water in the atmosphere. This acidity limits
the plant life that can survive near the volcano.
9. (a) Calcium oxide would react with water to form calcium hydroxide.
(b) The chemical equation for the reaction in (a) is: CaO(s) + H2O(l) → Ca(OH)2(aq)
(c) The solution would change from colourless to pink or magenta if the water contained
phenolphthalein indicator.
10. (b) Answers may vary. Sample answer: Carbon dioxide exhaled by visitors created carbonic
acid within the caves. The acidity reacted with the rock and pigment, causing the images to
deteriorate. To protect the art, visitors were no longer permitted to visit the caves. However, a
replica of the cave art was constructed to satisfy the interest of visitors.
Copyright © 2011 Nelson Education Ltd.
Chapter 5: Chemical Processes
5.3-1
11. Answers may vary. Sample answer: Ocean acidification is a recent phenomenon caused by
increased carbon dioxide in the atmosphere. The increased acidity is threatening shell-producing
animals as well as coral by reacting with the carbonate compounds from which the shells are
constructed. Coral secretes hard exoskeletons (shell-like material) to create the coral habitat and
to make the corals rigid.
Copyright © 2011 Nelson Education Ltd.
Chapter 5: Chemical Processes
5.3-2