Chapter 16

Chapter 16

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

____ 1. An oxidation reaction occurs only in the presence of _____.

a.	oxygen	c.	a metal
b.	hydrogen	d.	a reduction reaction

____ 2. The substance that is oxidized in the reaction Fe₂O₃ + 2Al ® Al₂O₃ + 2Fe is _____.

a.	Fe₂O₃	c.	Al
b.	Al₂O₃	d.	Fe

____ 3. A silver vase exposed to the air for a long time is most likely to have an outer coating of _____.

a.	silver metal	c.	silver oxide
b.	silver sulfide	d.	hydrogen sulfide

____ 4. Reduction is a(n) _____.

a.	redox reaction	c.	half-reaction
b.	loss of electrons	d.	agent

____ 5. In the equation Al + Cl₂ ® AlCl₃, the oxidation number of Al changes from _____ to _____.

a.	0, 3+	c.	0, 1-
b.	3+, 0	d.	-1, 0

____ 6. When iron is obtained from iron ore according to the equation 2Fe³⁺ + 3O^2- + 3CO ® 2Fe + 3CO₂, what is the reducing agent?

a.	Fe³⁺	c.	O^2-
b.	Fe	d.	C²⁺

____ 7. Chemiluminescent reactions release _____.

a.	heat	c.	odors
b.	light	d.	gases

____ 8. Is the following reaction a redox reaction? H₂SO₄ + 2NaOH ® Na₂SO₄ + 2H₂O

a.	yes	c.	if energy is added
b.	no	d.	It is impossible to determine.

____ 9. When silver reacts with sulfur to form tarnish, what element is the oxidizing agent?

a.	Ag	c.	S
b.	Ag⁺	d.	S^2-

____ 10. How do mammals keep from freezing during the winter?

a.	hibernation	c.	oxidation of fats stored in the body
b.	chemiluminescence	d.	combustion

Completion

Complete each sentence or statement.

11. In an oxidation-reduction reaction, oxygen gas is the ___________________ and ethane is the __________________.

12. A substance that gains electrons in a chemical reaction is known as a(n) ___________________.

13. In the reaction 2Fe + O₂ ® 2FeO, iron loses electrons to oxygen and is, therefore, a(n) ___________________.

14. A reaction like 2Fe + O₂ ® 2FeO, in which electrons are gained and lost by the reactants, is known as a(n) ______________________.

15. Hydrogen gas is used for some industrial operations because of its tendency to give up electrons, bringing about the chemical reaction known as _______________ in some other substance.

Matching

Match each item with the correct item below.

a.	reducing agent	f.	rust
b.	Ag⁰ ® Ag⁺ + e^-	g.	oxidation number = 0
c.	a common oxidizing agent	h.	reduction
d.	oxidation	i.	2-
e.	Fe³⁺ + 3e^- ® Fe⁰	j.	redox reaction

____ 16. loss of electrons

____ 17. gain of electrons

____ 18. Fe₂O₃

____ 19. an element in its free form

____ 20. always oxidized

Match each item with the correct item below.

a.	oxidizing agent	c.	both
b.	reducing agent

____ 21. O₂

____ 22. H₂

____ 23. CO

____ 24. I₂

____ 25. S^2-

Short Answer

26. Tell whether the following equation represents an oxidation or reduction half-reaction, then write in the correct value for X in the equation: H₂S ® SO₂ + X

27. The pig iron produced in a blast furnace always contains a small fraction of iron carbide, Fe₃C. Suggest a mechanism by which this compound is formed in the furnace.

28. In general, how can you tell whether or not a metal has been oxidized simply by looking at it?

Balance each equation for a half-reaction by rewriting the equation and inserting the correct coefficients needed.

29. F^-(aq) ® F₂(g) + e^-

30. In the following reaction, tell which element is oxidized and which is reduced. 2Na + Cl₂ ® 2NaCl

31. In the following reaction, tell which element is oxidized and which is reduced. C + 2S ® CS₂

32. In the following reaction, tell which element is oxidized and which is reduced.

2Al + 6HCl ® 2AlCl₃ + 3H₂

33. In the following reaction, tell which element is oxidized and which is reduced.

2H₂O₂ ® 2H₂O + O₂

34. In the equation Al + Cl₂ ® AlCl₃, write the balanced equation for the reduction half-reaction.

35. In the equation Al + Cl₂ ® AlCl₃, write the balanced equation for the oxidation half-reaction.