Crowe Exam Questions Ch.12 Reactions, Oxidation, Molecules

Chapter 12: Chemical reactions, oxidation, and reduction: bringing molecules to life

Test Bank

Type: multiple response question

Title: Chapter 12 - Question 01

1) Which of the following species behave as nucleophiles? Select all that apply.

a. Cl^–

b. H⁺

c. OH

d. CH₂CH₂

e. NO₂⁺

Type: multiple response question

Title: Chapter 12 - Question 02

2) Which of the following species behave as electrophiles? Select all that apply.

a. CN^–

b. CH₃CH₂⁺

c. H⁺

d. H₂O

e. CHCH

Type: multiple choice question

Title: Chapter 12 - Question 03

3) The stoichiometry of a reaction tells us which of the following?

a. The rate at which a reaction occurs.

b. The amount of energy liberated during the course of a reaction.

c. The number of steps from which an overall reaction, from reactants to products, is formed.

d. The amount of energy required to initiate a reaction.

e. The relative quantities of reactants and products associated with a particular reaction.

Type: multiple response question

Title: Chapter 12 - Question 04

4) Which of the following statements about chemical reactions are true? Select all that apply.

During chemical reactions, valence electrons do not always move in pairs. Instead, they can move singly, or in pairs, as explained in section 12.2.

The reactants associated with a particular reaction always react in the same relative quantities, regardless of reaction conditions. Temperature has no effect on the relative quantities involved. The relative quantities are denoted by the reaction’s stoichiometry, as explained in section 12.1.

a. Chemical reactions involve the breaking of bonds between atoms in molecules, and the formation of new bonds between different groups of atoms.

b. During chemical reactions, valence electrons always move as pairs.

c. The reactants associated with a particular reaction react in different relative quantities depending on the temperature at which the reaction is being performed.

d. Chemical reactions always result in full valence shells being maintained.

e. Chemical reactions require the movement of valence electrons.

Type: multiple response question

Title: Chapter 12 - Question 05

5) Which of the following statements about valence electrons are false? Select all that apply.

When heterolytic cleavage occurs, a pair of valence electrons is distributed unequally between two atoms (as explained in section 12.2).

Also, during a chemical reaction, valence electrons can move both within and between molecules. There are numerous examples within chapter 12 where electrons move both within and between molecules. Look at the mechanism below, for example: this shows electrons moving from one molecule to another, and between parts of the same molecule.

a. When heterolytic cleavage occurs, a pair of valence electrons is distributed unequally between two atoms.

b. We use a curly arrow to denote the movement of a pair of valence electrons.

c. The movement of valence electrons during a chemical reaction is random.

d. During a chemical reaction, valence electrons can move both within and between molecules.

e. The movement of valence electrons during a chemical reaction is described by the reaction scheme.

Type: multiple response question

Title: Chapter 12 - Question 06

6) Which of the following statements are true? Select all that apply.

An electrophile must possess (or be able to possess) a completely empty orbital rather than just a partially empty orbital, as described in section 12.3.

A non-bonding pair is a suitable valence pair for a nucleophile to donate.

And, when a nucleophile donates a pair of valence electrons to an electrophile, a covalent bond is formed, not an ionic bond.

a. An electrophile must possess a partially empty orbital.

b. A nucleophile must be able to donate a pair of valence electrons.

c. A non-bonding pair is not a suitable valence pair for a nucleophile to donate.

d. When a nucleophile donates a pair of valence electrons to an electrophile, an ionic bond is formed.

e. A double bond can act as a nucleophile.

Type: multiple choice question

Title: Chapter 12 - Question 07

7) The cleavage of the H—Br bond is most likely to generate which of the following pairs of species?

a. H⁺ and Br^–

b. H^– and Br⁺

c. H^• and Br^•

Type: multiple response question

Title: Chapter 12 - Question 08

8) Which of the following bonds are most likely to break homolytically? Select any that apply.

a. H–Br

b. Cl–Cl

c. C–H

d. C–C

e. O–H

Type: multiple choice question

Title: Chapter 12 - Question 09

9) Electromagnetic radiation in which of the following regions of the electromagnetic spectrum is most able to generate free radicals?

a. Radio wave

b. Cosmic wave

c. Infrared

d. Visible

e. Ultraviolet

Type: multiple choice question

Title: Chapter 12 - Question 10

10) The following reaction represents which stage in a free-radical reaction?

a. Initiation

b. Propagation

c. Termination

Type: multiple response question

Title: Chapter 12 - Question 11

11) Which of the following statements regarding free radicals are true? Select all that apply.

Antioxidants do not catalyse free radical reactions. In fact, the opposite is true: antioxidants inhibit free radical reactions.

Free-radical reactions involve homolytic bond cleavage, rather than heterolytic bond cleavage.

And it’s not strictly true to say that free radicals can only be generated from molecules possessing non-polar bonds. Non-polar bonds are more likely to undergo homolytic cleavage than polar bonds (to form two free radicals), but a free radical is able to attack a molecule containing polar bonds to generate further free radicals. For example, the propagation step shown in Figure 12.13 depicts a free radical attacking a polar C–H bond.

a. Antioxidants catalyse free radical reactions by encouraging the formation of free radicals.

b. A chain reaction involves a sequence of linked propagation reactions.

c. Free-radical reactions involve heterolytic bond cleavage.

d. Free radicals can only be generated from molecules possessing non-polar bonds.

e. The initiation of a free-radical reaction by ultraviolet light is called photolysis.

Type: multiple choice question

Title: Chapter 12 - Question 12

12) When we forcibly increase the proportion of free radicals entering the termination step of a free-radical reaction we are said to be doing what?

a. Extinguishing the reaction

b. Terminating the reaction

c. Quenching the reaction

d. Exhausting the reaction

e. Expunging the reaction

Type: matching question

Title: Chapter 12 - Question 13

13) Match the correct terms with the following descriptions.

Feedback: Oxidation and reduction are coupled processes: the loss of electrons from one species (oxidation) must be coupled to the gain of the same electrons by another species (reduction).

Page reference: section 12.5

a. A loss of electrons during the course of a reaction = Oxidation

b. A gain of electrons during the course of a reaction = Reduction

Type: true-false

Title: Chapter 12 - Question 14

14) During the process NADH → NAD⁺ the electron carrier NAD is being reduced. True or false?

a. True

b. False

Type: multiple choice question

Title: Chapter 12 - Question 15

15) Based on the following standard reduction potentials, which of the following species acts as the strongest oxidizing agent?

Zn²⁺(aq) + 2e^- ⇌ Zn(s)_; E° = -0.34v

Cl₂(g) + 2e^- ⇌ 2Cl^-(aq); E° = 1.36v

Ca²⁺(aq) + 2e^- ⇌ Ca(s); E° = -2.87v

2H⁺(aq) + 2e^- ⇌ H₂(g); E° = 0.00v

a. Zn²⁺(aq)

b. Cl₂(g)

c. Ca²⁺(aq)

d. 2H⁺(aq)

Type: multiple choice question

Title: Chapter 12 - Question 16

16) The reference electrode against which other standard reduction potentials are measured is which of the following?

a. The platinum electrode

b. The iron electrode

c. The copper electrode

d. The zinc electrode

e. The hydrogen electrode

Type: multiple choice question

Title: Chapter 12 - Question 17

17) During the course of a reaction, the oxidation number of oxygen increases from -2 to 0. Is oxygen being oxidized or reduced during this reaction?

a. Oxidized

b. Reduced