Chapter 11 Homework

Question 1

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

Answer 1

+4, −2

Question 2

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

Answer 2

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 3

What is wrong with the following incorrectly balanced reaction?

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

Answer 3

The coefficient on I 2 should be 1.

Question 4

Given the reaction:
Zn(s) + 2AgNO3(aq) → Zn(NO3 )2(aq) + 2Ag(s)

Which of the following statements is correct?

Answer 4

Silver nitrate is the oxidizing agent.

Question 5

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 5

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 6

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

H2S(aq) → S(s)

Answer 6

H2S(aq) → S(s) + 2H + (aq) + 2e −

Question 7

What are the oxidation numbers for magnesium and oxygen (in that order) in the MgO molecule?

Answer 7

+2, −2

Question 8

What is an oxidation state?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

Which statement about the following redox reaction in acidic solution is not correct?

H2S(aq) + Cr2O72− (aq) → S(s) + Cr3+ (aq)

Answer 10

The final step involves adding oxygen atoms to the left side of the reaction and hydrogen atoms to the right side of the reaction

Question 11

Which of the following best describes what a redox reaction is?

Answer 11

It is a reaction in which the oxidation state of one element increases and the oxidation state of another element decreases.

Question 12

Which of the following correctly shows the oxidation numbers for the elements in Mn3(PO4 )2?
(The phosphate ion is written alone as PO43−.)

Answer 12

O = −2; P = +5; Mn = +2

Question 13

Which of the following correctly identifies the oxidizing agent, the reducing agent, the oxidized substance, and the reduced substance in the reaction?

6Fe2+(aq) + Cr2O72−(aq) + 14H +(aq) → 6Fe3+(aq) + 2Cr3+(aq) + 7H2O(l)

Answer 13

Cr2O72− is the oxidizing agent. Fe2+ is the reducing agent. Fe2+ is the oxidized substance. Cr2O72− is the reduced substance.

Question 14

Which statement about balancing this simple redox reaction using the half-reaction method is correct?

Cu(s) + Ag+1 (aq) → Cu+2 (aq) + Ag(s)

Answer 14

At the end of the balancing method, the total number of electron transfers for each of the two half-reactions is the same.

Question 15

Which of the following correctly describes the two half-reactions in the redox reaction below?

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

Answer 15

CuS(s)→ Cu2+ (aq) + SO42− + 8e − is the oxidation step.

NO3− (aq) + 3e −→ NO(g) is the reduction step.

Question 16

Look at the unbalanced redox reaction (in an acidic solution).

S2O32− (aq) + I2(aq) → SO42− (aq) + I − (aq)

Which of the following is not part of the final balanced reaction?

Answer 16

10H2O(l)

Question 17

How does assigning oxidation states in compounds help you balance redox reactions?

Answer 17

The oxidation state tells you about an atom or molecule’s potential to accept or donate electrons.

Question 18

This list of reduction reactions is a helpful tool for predicting how two metals will interact with one another. Suppose that we are looking for a metal to react in a specific manner with magnesium. Which of the following correctly describes and lists the metal that will achieve our desired goal?

Answer 18

We want a metal that will cause magnesium ion(Mg2+ ) to be reduced spontaneously. We choose calcium metal.

Question 19

In an expanded redox activity series, aluminum is located above iron. Which statement correctly predicts what will happen (or not happen) when these two metals and its cations interact?

Answer 19

Aluminum will act as the stronger reducing agent and iron metal ion will act as the stronger oxidant.