Chapter 18 Practice Test

Question 1

What happens when a heterolytic bond is broken?

Answer 1

One atom gets a pair of electrons.

Question 2

In the following generalized reaction, which of the atoms receives the electrons from the cleavage of the A–H bond?
(A=C, N, O…)

δ− A–H δ+ + :B → A− + H–B+

Answer 2

A

Question 3

Which acid is the strongest?

Answer 3

Hydroiodic acid

Question 4

If hydrobromic acid were homolytically cleaved, how many electrons would go to the hydrogen atom?

Answer 4

1

Question 5

If X is electron-rich in the molecule, X—O–H, which bond is polarized?

Answer 5

X—O

Question 6

Arrange the following oxoacids from the weakest to the strongest acid:
HClO hypochlorous acid HClO2 chlorous acid HIO hypoiodous acid HBrO hypobromous acid
The electronegativity values for constituent elements are:
H 2.1 O 3.5 I 2.5 Br 2.8 Cl 3.0

Answer 6

hypoiodous acid < hypobromous acid < hypochlorous acid < chlorous acid

Question 7

Which has the lowest pKa value?

Answer 7

Ethyne

Question 8

What orbitals comprise a C–H bond in the methyl group of ethane?

Answer 8

One sp3 orbital of carbon and a 1s of hydrogen

Question 9

Which bonds in cyclohexane have more p character?

Answer 9

C–C

Question 10

Which of the following is the LEAST acidic?

Answer 10

Propane

Question 11

Which of the following is a resonance structure for the benzene molecule?

Answer 11

Question 12

Which of the following is an alcohol?

Answer 12

Question 13

Study the diagrams of the relative electron densities of various chlorine oxoacids. Which is the weakest acid in the group?

Answer 13

Acid 1

Question 14

What is the type of bond cleavage that leads to proton release called?

Answer 14

Heterolytic cleavage

Question 15

Using the electronegativity values for the following elements, calculate which compound should be the weakest acid based on electronegativity values alone.
H = 2.1, C = 2.5, N = 3.0, O = 3.5, F = 4.0
Compounds: methane, ammonia, water, hydrofluoric acid

Answer 15

Methane

Question 16

In comparing three organic nitrogen compounds pictured below, we find that the conjugate acid of the nitrile is the most acidic molecule. Which compound is the strongest base?

Answer 16

The amine

Question 17

Organic chemists use a sort of chemical short hand when drawing the structural formulas for organic compounds. What is one way of writing the complete formula for the following cation?

Answer 17

C7H7+

Question 18

What is the steric number for ClF3?

Answer 18

5

Question 19

Boron, a nonmetal, which can form covalent compounds, is found in covalent hydrides called boranes. Boranes are extremely electron deficient and are highly reactive Lewis acids. Which borane is the simplest known hydride of boron?

Answer 19

B2H6

Question 20

Which of the following accurately illustrates the correct Lewis structures of the NO3− ion?

Answer 20

none of the above

Question 21

In the following reaction, which is a Lewis acid?

CO2 + OH − → HCO3−

Answer 21

CO2

Question 22

Which of the following is a nucleophile?

Answer 22

Lewis base

Question 23

In the following reaction progress chart, identify the rate-determining step.

Answer 23

TS2

Question 24

Which of the following isotopes is frequently used in choosing between different reaction mechanisms?

Answer 24

Oxygen-18

Question 25

Which carbon in the diagram below is the most electrophilic carbon in the molecule?

Answer 25

Carbon 3