Deck 15: Oxidation and Reduction

Question 1

Which of the following statements is not true of a redox reaction?

A) The reducing agent is the substance oxidized.
B) The reducing agent gains electrons.
C) The substance oxidized loses electrons.
D) The oxidizing agent is the substance reduced.

Answer 1

The reducing agent gains electrons.

Question 2

In the following reaction H₂SO₄ is ________.
H₂SO₄ + HI $\rightarrow$ I₂ + SO₂ + H₂O

A) the oxidizing agent and is oxidized
B) the oxidizing agent and is reduced
C) the reducing agent and is oxidized
D) the reducing agent and is reduced

Answer 2

the oxidizing agent and is reduced

Question 3

Indicate the missing words (or phrases) in the following definition: "An oxidation number is the ________ that an atom ________ when the electrons in each bond it is participating in are assigned to the ________ electronegative of the two atoms involved in the bond."

A) number of electrons, definitely has, more
B) number of electrons, appears to have, less
C) charge, appears to have, more
D) charge, definitely has, less

Answer 3

charge, appears to have, more

Question 4

The proper assignment of oxidation numbers to the elements in Na₂CrO₄ would be ________.

A) +1 for Na, +6 for Cr and -2 for O
B) +2 for Na, +4 for Cr and -6 for O
C) +2 for Na, +3 for Cr and -2 for O
D) +2 for Na, +5 for Cr and -6 for O

Question 5

+7 is the oxidation number of ________.

A) C in MgC₂O₄
B) S in H₂SO₄
C) Mn in KMnO₄
D) Br in NaBrO₃

Question 6

The oxidation number of C in BaC₂O₄ is ________.

A) -3
B)-2
C) +2
D) +3

Question 7

The oxidation number of Cr in K₂Cr₂O₇ is ________.

A) +6
B) +5
C) +4
D) +2

Question 8

In which of the following compounds does Cl have an oxidation number of +7?

A) LiClO₃
B) Al(ClO₄)₃
C) Ca(ClO₃)₂
D) NaClO₂

Question 9

In which of the following sequences of sulfur-containing species are the species arranged in order of decreasing oxidation number for S?

A) SO₃^2-, SO₄^2-, S^2-
B) SO₄^2-, S₂O₃^2-, S^2-
C) S₂O₃^2-, SO₃^2-, S^2-
D) SO₄^2-, S^2-, S₂O₃^2-

Question 10

In which of the following compounds is the oxidation number of oxygen not ?2?

A) Ba(OH)₂
B) Li₂O₂
C) NaClO₂
D) Na₂SO₄

Question 11

In which of the following compounds is the oxidation number of hydrogen not +1?

A) NaH
B) H₂SO₄
C) NaClO₂
D) NH₃

Question 12

The pure element zinc has an oxidation number of ________, while in a compound like ZnSO₄ the oxidation number for zinc is ________.

A) 0, 0
B) 0, +1
C) +1, 0
D) 0, +2

Question 13

In the redox reaction: Al + MnO₂ $\rightarrow$ Al₂O₃ + Mn, the oxidizing agent is ________.

A) Al
B) Mn in MnO₂
C) O in MnO₂
D) O in Al₂O₃

Question 14

In a redox reaction, the substance reduced ________.

A) contains an element which increases in oxidation number
B) is also the reducing agent
C) always gains electrons
D) always loses electrons

Question 15

In the redox reaction: BaSO₄ + 4 C $\rightarrow$ BaS + 4 CO, the element reduced is ________.

A) S in BaSO₄
B) C
C) Ba in BaS
D) O in CO

Question 16

Which of the following accurately represents the oxidation of the Co⁺² ion?

A) Co⁺² + 2 e^- $\rightarrow$ Co
B) Co⁺² $\rightarrow$ Co⁺³ + e^-
C) Co $\rightarrow$ Co⁺² + 2 e^-
D) Co⁺³ + e^- $\rightarrow$ Co⁺²

Question 17

Which reaction below can be classified as a redox/decomposition reaction?

A) 2 CuO $\rightarrow$ 2 Cu + O₂
B) 2 NO + O₂ $\rightarrow$ 2 NO₂
C) Sn + Cu(NO₃)₂ $\rightarrow$ Sn(NO₃)₂ + Cu
D) Cu(NO₃)₂ + 2 NaOH $\rightarrow$ Cu(OH)₂ + 2 NaNO₃

Question 18

Which of the following equations is incorrectly classified as to type of chemical reaction?

A) CaCO₃ $\rightarrow$ CaO + CO₂ decomposition/redox
B) H₂O + SO₂ $\rightarrow$ H₂SO₃ synthesis/nonredox
C) Cl₂ + F₂ $\rightarrow$ 2 ClF synthesis/redox
D) AgNO₃ + NaCl $\rightarrow$ AgCl + NaNO₃ double-displacement/non-redox

Question 19

Which of the following equations is incorrectly classified as to type of chemical reaction?

A) NaHCO₃ + HCl $\rightarrow$ NaCl + H₂O + CO₂ double-replacement/nonredox
B) 2 Na + H₂ $\rightarrow$ 2 NaH synthesis/redox
C) PbO + C $\rightarrow$ Pb + CO single-replacement/nonredox
D) 2 Na + 2 HCl $\rightarrow$ 2 NaCl + H₂ single-replacement/redox

Question 20

Determine the oxidation number of C in NaHCO₃.

A) +6
B) +12
C) +4
D) +5

Question 21

Determine the oxidation number of the underlined element in NaBrO₄.

A) +7
B) +4
C) -6
D) -4

Question 22

In which of the following compounds does nitrogen have an oxidation number of +4?

A) HNO₃
B) NO₂
C) N₂O
D) NH₄Cl

Question 23

The following reactions are classified first as redox or nonredox. They are further classified as synthesis, decomposition, single replacement, or double displacement reactions. Which of the following reactions is incorrectly classified as to redox/nonredox or as to synthesis, decomposition, single-replacement, or double-displacement (precipitation) reactions?

A) HNO₃(aq) + LiOH(aq) $\rightarrow$ LiNO₃ (aq) + H₂O(l) non-redox / double-displacement
B) Pb(NO₃)₂(aq) + 2 Na(s) $\rightarrow$ Pb(s) + NaNO₃(aq) redox / single-replacement
C) 2 H₂O₂(l) $\rightarrow$ 2 H₂O(l) + O₂(g) non-redox / decomposition
D) AgNO₃(aq) + KOH(aq) $\rightarrow$ KNO₃(aq) + AgOH(s) non-redox / precipitation

Question 24

Which of the following reactions is a redox single replacement reaction?

A) Zn + H₂SO₄ $\rightarrow$ H₂ + ZnSO₄
B) 2 KClO₃ $\rightarrow$ 2 KCl + O₂
C) 2 NO₂ + H₂O₂ $\rightarrow$ 2 HNO₃
D) SO₃ + H₂O $\rightarrow$ H₂SO₄

Question 25

Which of the following reactions is not a redox reaction?

A) SO₃ + H₂O $\rightarrow$ H₂SO₄
B) 2 Na + Mg²⁺ $\rightarrow$ Mg + 2 Na⁺
C) Cl₂ + 2I^- $\rightarrow$ 2 Cl^- + I₂
D) Na + AgNO₃ $\rightarrow$ NaNO₃ + Ag

Question 26

In the redox reaction: 4 Cr + 3 O₂ + 12 HBr $\rightarrow$ 4 CrBr₃ + 6 H₂O the change in oxidation number for O is from ________.

A) +4 to -4
B) +2 to 0
C) 0 to -2
D) +3 to 0

Question 27

In the redox reaction: 2 HNO₂ + 2 HI $\rightarrow$ 2 NO + I₂ + 2 H₂O, ________.

A) HNO₂ is the oxidizing agent.
B) HNO₂ is the substance oxidized.
C) I undergoes an oxidation number increase of 2 units per atom.
D) N undergoes an oxidation number increase of 2 units per atom.

Question 28

In the following reaction: 2 Mn⁺² + Br₂ $\rightarrow$ 2 Mn⁺³ + 2 Br^- the species that is oxidized is ________.

A) Mn²⁺
B) Br^-
C) Mn⁺³
D) Br₂

Question 29

In the following reaction, which species is the reducing agent?
3 Cu (s) + 6 H⁺ (aq) + 2 HNO₃ (aq) $\rightarrow$ 3 Cu⁺² (aq) + 2 NO (g) + 4 H₂O (l)

A) H⁺
B) Cu
C) N in NO
D) Cu⁺²

Question 30

Which substance is serving as the reducing agent in the following reaction?
Fe₂S₃ + 12 HNO₃ $\rightarrow$ 2 Fe(NO₃)₃ + 3 S + 6 NO₂ + 6 H₂O

A) HNO₃
B) S
C) NO₂
D) Fe₂S₃

Question 31

In the following reaction: 2 Al (s) + 3 I₂ (s) $\rightarrow$ 2 AlI₃ (s) which species is the oxidizing agent?

A) Al
B) AlI₃
C) I₂
D) none of the species

Question 32

Which substance is serving as the reducing agent in the following reaction?
14H⁺ + Cr₂O₇^-2 + 3 Ni $\rightarrow$ 3 Ni²⁺ + 2 Cr⁺³ + 7 H₂O

A) Ni
B) H⁺
C) Cr₂O₇^-2
D) H₂O

Question 33

Which substance is serving as the oxidizing agent in the following reaction?
14H⁺ + Cr₂O₇^-2 + 3 Ni $\rightarrow$ 3 Ni²⁺ + 2 Cr⁺³ + 7 H₂O

A) Ni
B) H⁺
C) Cr₂O₇^-2
D) H₂O

Question 34

How many electrons are lost or gained by each formula unit of CuBr₂ in the reaction
Zn + CuBr₂ $\rightarrow$ ZnBr₂ + Cu

A) gains 2 electrons
B) loses 2 electrons
C) loses 1 electron
D) gains 6 electrons

Question 35

Which of the following is a correctly balanced oxidation half-reaction?

A) H₂C₂O₄ $\rightarrow$ 2 CO₂ + 2 H⁺ + 2e^?
B) I₂ + 2e^- $\rightarrow$ 2 I^-
C) HOCl + H⁺ + 2e^- $\rightarrow$ Cl^- + H₂O
D) H₂S $\rightarrow$ S + 2 H⁺ + 4e^-

Question 36

The balanced full-equation obtained by adding the following two balanced half-reactions is ________.
2H₂O + PH₃ $\rightarrow$ H₃PO₂ + 4H⁺ + 4e^-
I₂ + 2e^- $\rightarrow$ 2I^-

A) 2 H₂O + PH₃ + I₂ $\rightarrow$ H₃PO₂ + 4 H⁺ + 2 I^- + 2 e^-
B) 4 H₂O + 2 PH₃ + I₂ $\rightarrow$ 2 H₃PO₂ + 8 H⁺ + 2 I^-
C) 2 H₂O + PH₃ + 2 I₂ $\rightarrow$ H₃PO₂ + 8 I^- + 8 H⁺
D) 2 H₂O + PH₃ + 2 I₂ $\rightarrow$ H₃PO₂ + 4 I^- + 4 H⁺

Question 37

When the half-reaction: MnO₄^- $\rightarrow$ Mn²⁺ (acidic solution) is correctly balanced, ________.

A) the H⁺ and H₂O are both on the left side of the equation
B) the H⁺ and H₂O are both on the right side of the equation
C) the H⁺ is on the left side, and the H₂O on the right side of the equation
D) the H⁺ is on the right side, and the H₂O on the left side of the equation

Question 38

When the redox reaction: NF₃ + AlCl₃ $\rightarrow$ N₂ + Cl₂ + AlF₃ is balanced, the correct coefficients for NF₃ and Cl₂, respectively, are ________.

A) 3 and 4
B) 4 and 2
C) 2 and 3
D) 6 and 3

Question 39

When the redox reaction: Zn + As₂O₃ $\rightarrow$ AsH₃ + Zn²⁺ (acidic solution) is balanced, the correct coefficients for H₂O, H⁺ and AsH₃ are, respectively, ________.

A) 6, 6 and 3
B) 6, 3 and 12
C) 3, 12 and 2
D) 4, 8 and 3

Question 40

When the following equation is balanced, by the half reaction method, in an acidic solution what is the sum of the coefficients?
HNO₂ + Cr₂O₇^-2 $\rightarrow$ Cr⁺³ + NO₃^-

A) 17
B) 18
C) 19
D) 20

Question 41

Which is the balanced half reaction in basic solution for the reaction below?
Cr(OH)₄^- $\rightarrow$ CrO₄^2-

A) 3 e^- + Cr(OH)₄^- + 2 OH^- $\rightarrow$ Cr(OH)₄^- + 2 H₂O
B) 4 OH^- + Cr(OH)₄^- $\rightarrow$ CrO₄^2- + 3e^- + 4 H₂O
C) 2 OH^- + Cr(OH)₄^- $\rightarrow$ CrO₄^2- + 6 e^- + 3 H₂O
D) Cr(OH)₄^- $\rightarrow$ CrO₄^2- + 4 H₂O + 2 e^-

Question 42

Which reaction is the correctly balanced half reaction (in acid solution) for the process below?
Cr₂O₇^2- (aq) $\rightarrow$ Cr³⁺ (aq)

A) 14 H⁺ + Cr₂O₇^2- + 6 e^- $\rightarrow$ 2 Cr³⁺ + 7 H₂O
B) 8 H⁺ + Cr₂O₇ + 3 e^- $\rightarrow$ 2Cr³⁺ + 4 H₂O
C) 8 H⁺ + Cr₂O₇ $\rightarrow$ 2 Cr³⁺ + 4 H₂O + 3 e^-
D) 12 H⁺ + Cr₂O₇^2- + 3 e^- $\rightarrow$ 2 Cr³⁺ + 6 H₂O

Question 43

Which response represents the balanced half reaction for oxidation for the reaction given below?
HCl (aq) + Fe (s) $\rightarrow$ FeCl₃ (aq) + H₂ (g)

A) 6 e^- + 6 H⁺ $\rightarrow$ 3 H₂
B) 2 Fe $\rightarrow$ 2 Fe³⁺ + 6 e^-
C) 3 Fe $\rightarrow$ Fe³⁺ + 3 e^-
D) Fe + 3 e^- $\rightarrow$ Fe³⁺

Question 44

Which response represents the balanced half reaction for reduction for the reaction given below?
Fe (s) + CuSO₄ (aq) $\rightarrow$ Fe₂(SO₄)₃ (aq) + Cu (s)

A) 2 Cu²⁺ + 3 e^- $\rightarrow$ 2 Cu
B) Fe + 3 e^- $\rightarrow$ Fe³⁺
C) 3 Cu²⁺ + 6 e^- $\rightarrow$ 3 Cu
D) 2 Fe $\rightarrow$ 2 Fe³⁺ + 6e^-

Question 45

Balance the following net ionic equation using the half reaction method (in acidic solution). What is the coefficient for MnO₄^-?
H⁺ + Fe²⁺ + MnO₄^- $\rightarrow$ Fe³⁺ + Mn²⁺ + H₂O

A) 8
B) 5
C) 1
D) 14

Question 46

Balance the following net ionic equation using the half reaction method (in acidic solution). What is the sum of the coefficients for the balanced reaction?
MnO₄^- + SO₃^2- $\rightarrow$ Mn²⁺ + SO₄^2-

A) 27
B) 29
C) 21
D) 23

Question 47

Which of the following reactions is a disproportionation reaction?

A) 2 H₂O $\rightarrow$ 2 H₂ + O₂
B) H₂SO₃ $\rightarrow$ H₂O + SO₂
C) HNO₂ $\rightarrow$ NO + NO₃^-
D) Mg + H₂SO₄ $\rightarrow$ MgSO₄ + H₂

Question 48

In balancing the equation for a disproportionation reaction, using the oxidation number method, the substance undergoing disproportionation is ________.

A) initially written twice on the reactant side of the equation
B) initially written twice on the product side of the equation
C) initially written on both the reactant and product sides of the equation
D) always assigned an oxidation number of zero

Question 49

In the disproportion equation below, what species is undergoing disproportionation?
3 Br₂ + 6 OH^- $\rightarrow$ BrO₃^- + 5 Br^- + 3 H₂O

A) OH^-
B) Br^-
C) H₂O
D) Br₂

Question 50

Which of the following formula unit or net ionic equations represents a disproportionation reaction?

A) Fe + 3 Ag⁺ $\rightarrow$ Fe³⁺ + 3 Ag
B) 2 HNO₃ + SO₂ $\rightarrow$ H₂SO₄ + 2 NO₂
C) ClO^- + Cl^- + 2 H⁺ $\rightarrow$ Cl₂ + H₂O
D) CH₄ + 2 O₂ $\rightarrow$ CO₂ + H₂O

Question 51

Which of the following is a correct statement about galvanic cells?

A) Chemical energy is converted entirely into heat energy.
B) They are always based on a nonspontaneous redox reaction.
C) They may employ an oxidation process or a reduction process but never both.
D) Electrical energy is produced from a spontaneous redox reaction.

Question 52

The anode in a galvanic or electrolysis cell is ________.

A) the compartment where solution is placed
B) the electrode where electrons leave the cell
C) the electrode where reduction takes place
D) always the oxidizing agent for the reaction

Question 53

In a galvanic cell, the cathode is the electrode at which ________ occurs?

A) oxidation
B) reduction
C) oxidation and reduction
D) nothing

Question 54

Which of the following is not correct for both acidic and alkaline dry cells?

A) As the name implies, the electrolyte is a dry material.
B) The anode reaction involves Zn.
C) The cathode reaction involves MnO₂.
D) The cathode is an inert material.

Question 55

Which of the following statements concerning the lead storage battery is incorrect?

A) PbSO₄ is produced during the discharging of the battery.
B) PbO₂ is consumed during the recharging of the battery.
C) Pb serves as the anode.
D) Pb coated with PbO₂ serves as the cathode.

Question 56

During the recharging of a lead storage battery, what products(s) are formed?

A) PbO₂ (s) and PbSO₄ (s)
B) Pb (s) and PbO₂ (s)
C) Pb (s) only
D) PbO₂ (s) only

Question 57

Which statement is incorrect?

A) Reduction occurs at the anode in an electrolytic cell.
B) Electroplating is the deposition of a thin layer of metal on an object.
C) During recharging the lead storage battery is functioning as an electrolytic cell.
D) Electrolysis is a process in which electrical energy is used to cause a nonspontaneous reaction to occur.

Question 58

In the reactions below, which reaction correctly identifies the anode reaction during the discharging (normal usage) of a lead storage battery cell?

A) Pb + SO₄^2- $\rightarrow$ PbSO₄ + 2 e^-
B) Zn + 2 OH^- $\rightarrow$ ZnO + H₂O + 2 e^-
C) 2 MnO₂ + H₂O + 2 e^- $\rightarrow$ Mn₂O₃ + 2 OH^-
D) PbO₂ + 4 H⁺ + SO₄^2- + 2 e^- $\rightarrow$ PbSO₄ + 2 H₂O

Question 59

What is the cathode material in a common dry cell such as a flashlight battery?

A) lead
B) graphite
C) zinc
D) magnesium

Question 60

Assign an oxidation number to each atom in the following chemical reaction.
As₂O₃ + 5 H₂O + 2 I₂ ? 2 H₃AsO₄ + 4 HI

Question 61

Identify which substance is oxidized and which substance is reduced in the following chemical reaction.
4 NH₃ + 3 O₂ → 2 N₂ + 6 H₂O

Question 62

Indicate whether each of the following formula unit or net ionic equations is or is not a redox reaction by writing the word

-NH₄⁺(aq) + CN^-(aq) $\rightarrow$ HCN(aq) + NH₃(aq) ____________________

A) non-redox
B) redox

Question 63

Indicate whether each of the following formula unit or net ionic equations is or is not a redox reaction by writing the word

-2 Al(s) + 3 FeO(s) $\rightarrow$ 3 Fe(s) + Al₂O₃(s) ____________________

A) non-redox
B) redox

Question 64

Indicate whether each of the following formula unit or net ionic equations is or is not a redox reaction by writing the word

-N₂(g) + 3 H₂(g) $\rightarrow$ 2 NH₃(g) ____________________

A) non-redox
B) redox

Question 65

Indicate whether each of the following formula unit or net ionic equations is or is not a redox reaction by writing the word

-Ag⁺(aq) + Cl^-(aq) $\rightarrow$ AgCl(s) ____________________

A) non-redox
B) redox

Question 66

Balance the following equation by the oxidation-number method.
Fe₂O₃ + CO → Fe + CO₂

Question 67

Balance the following half reaction in basic solution.
S^2? ? SO₃^2?

Question 68

Balance the following half reaction in acidic solution.
NO₃^? ? NO

Question 69

Write the balanced half reactions for oxidation and reduction for the following chemical equation.
Fe (s) + Cu(NO₃)₂ (aq) → Fe(NO₃)₃ (aq) + Cu (s)

Question 70

Balance the following reactions for the solution type indicted. Be sure to identify which is oxidized and reduced.