Chapter 11 Test

Question 1

What are the oxidation numbers of potassium, sulfur, and oxygen, respectively, in K2SO4?

Answer 1

+1, +6, −2

Question 2

Consider the combustion of methane to form carbon dioxide and water. What is the oxidation state change for carbon in this reaction?

Answer 2

from −4 to +4

Question 3

Permanganate can be used to oxidize oxalic acid all the way to carbon dioxide. If you balance this redox reaction in acidic solution, which of the following statements about the balanced reaction is not true?

MnO4− (aq) + H2C2O4(aq) → Mn2+ (aq) + CO2(aq)

Answer 3

Each equivalent of MnO4− will react with 5 equivalents of oxalic acid

Question 4

Which of the following half-reactions is an oxidation half-reaction?

Answer 4

Mn(s) ->Mn2+(aq) + 2e-

Question 5

Balance the following redox reaction in acid. What is the coefficient on H +?

CuS(s) + NO3− (aq) →
Cu2+ (aq) + SO42− (aq) + NO(g)

Answer 5

8

Question 6

Suppose that you have to balance the following half-reaction in basic solution.

Cr2O72− (aq) → Cr3+ (aq)

What is the coefficient on water of the final balanced half-cell reaction?

Answer 6

7

Question 7

The redox activity series lists reactions as
M n+ + n e − → M
with lithium at the top and gold at the bottom. Which statement best describes the redox activity series?

Answer 7

It is easiest to oxidize elements at the top of the list and it gets harder as you go down the series.

Question 8

Zinc can displace lead ions from solution in the following manner:

Zn(s) + Pb2+ (aq) → Zn2+ (aq) + Pb(s)

In an expanded redox activity series, the reaction of Pb2+ (aq) + 2e− → Pb(s) is located below the reaction of Zn2+ (aq) + 2e− → Zn(s).
Which of the following best explains why this reaction is spontaneous or nonspontaneous?

Answer 8

The reaction is spontaneous because zinc is a better reducing agent than lead

Question 9

What is the principal difference between balancing a redox reaction in acidic solution and balancing a redox reaction in basic solution?

Answer 9

To balance a redox reaction in acidic solution, we add the appropriate amounts of H + and H2O. To balance a redox reaction in basic solution, we add the appropriate amounts of OH − and H2O.

Question 10

What are the oxidation states (oxidation numbers) for carbon and oxygen, respectively, in carbonate ion, CO32−?

Answer 10

+4, −2

Question 11

What are the total oxidation numbers for atoms of K, O and Cl, respectively, in KClO3, potassium chlorate, used in fireworks?

Answer 11

+1, −2, +5

Question 12

Which of the following shows (in the correct order) the oxidation numbers for phosphorous (P) and oxygen (O) in the polyatomic ion PO43−?

Answer 12

+5, −2

Question 13

What is wrong with the following incorrectly balanced reaction?

2HNO2(aq) + 2HI(aq) → 2NO(g) + 2I2(aq) + 2H2O(l)

Answer 13

The coefficient on I 2 should be 1.

Question 14

Balance the following redox reaction in acid. What is the coefficient on water and on what side of the reaction does it appear?

Cr3+ (aq) + ClO3− (aq) → Cl − (aq) + CrO42− (aq)

Answer 14

5 waters on the reactants side

Question 15

The reaction of copper and silver nitrate is spontaneous.

Cu(s) + 2AgNO3(aq) →
Cu(NO3 )2(aq) + 2Ag(s)

The reverse reaction, in which silver metal is placed in the copper nitrate solution, is not spontaneous.

Which statement best describes the oxidizing and reducing abilities of the reactants?

Answer 15

Silver ion (Ag+ ) is a stronger oxidizing agent than copper ion (Cu2+ ) and copper metal is a stronger reducing agent than silver.

Question 16

Which statement about oxidation states (or numbers) is not correct?

Answer 16

Because the electronegativity difference can be small, electronegativity is not an important consideration when determining oxidation states.

Question 17

Look at the oxidation numbers assigned for the ammonium ion, NH4+.

NH	+
4
−3 + 4 (+1) = +1
ammonium ion 

Which of the following statements is not correct?

Answer 17

An electron deficient atom such as nitrogen will welcome the four hydrogen atoms because of the electronegativity difference.

Question 18

What is an oxidation state?

Answer 18

It is a charge assigned to an atom. It tells you how many electrons the atom controls in a compound.

Question 19

Which statement about the following (unbalanced) redox reaction in basic solution is not correct?

Al(s) + OH − (aq) → Al(OH)4− (aq) + H2(g)

Answer 19

The oxidation state for hydrogen goes from +1 → −1.

Question 20

Look at the reaction between oxalate and iodate ions 5C2O42-(aq) + 2IOe-(aq) + 12H+(aq) -> 10CO2(g) + I2(aq) + 6H2O(l) Which of the following correctly identifies the oxidizing agent, the reducing agent, the oxidized compound, and the reduced compound

Answer 20

IO3− is the oxidizing agent and the reduced compound.

C2O42− is the reducing agent and the oxidized compound.

Question 21

Which of the following correctly shows the oxidation numbers for each of the elements in H2PO4−, I2, and Al(OH)4−?

Answer 21

H2PO4−: H = +1, P = +5, O = −2; I2 : I = 0; Al(OH)4− : Al = +3; O = −2; H = +1

Question 22

Which of the following shows the fully balanced version of the following half-reaction in acidic solution?

H2S(aq) → S(s)

Answer 22

H2S(aq) → S(s) + 2H + (aq) + 2e −

Question 23

Suppose that you have to balance the following reaction in basic solution.

Bi2O3(s) + ClO− (aq) → BiO3− (aq) + Cl − (aq)

What is the coefficient on OH − in the balanced reaction?

Answer 23

2

Question 24

When Cu(NO3 )2(aq) reacts with Zn(s), Cu(s) is a product.

Cu(NO3 )2(aq) + Zn(s) → Cu(s) + Zn(NO3 )2(aq)

Which statement best describes what happened in this redox reaction?

Answer 24

Cu2+, as an oxidizing agent, causes Zn(s) to be oxidized to Zn2+ (aq). Zn(s), as a reducing agent, causes Cu2+ (aq) to be reduced to Cu(s).

Question 25

Suppose that zinc metal and magnesium metal are placed in a solution of zinc ions and magnesium ions. Which statement correctly predicts and explains what will happen?

Note that in the activity series
Mg2+ (aq) + 2e− → Mg(s)
is above
Zn2+ (aq) + 2e− → Zn(s)

Answer 25

The zinc ions will gain electrons in the reaction.