Question 1

Which of the following statements best describes a saturated hydrocarbon?

Accepted Answer

A hydrocarbon containing only carbon-carbon single bonds.

Question 2

What is the general molecular formula for an unbranched alkane?

Accepted Answer

$$\mathrm{C}_n\mathrm{H}_{2n+2}$$

Question 3

Which of the following is a constitutional isomer of butane ($$\mathrm{C}_4\mathrm{H}_{10}$$)?

Accepted Answer

2-Methylpropane

Question 4

According to IUPAC nomenclature, what is the correct name for the following structure: $$\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}(\,\mathrm{CH}_3)\mathrm{CH}_2\mathrm{CH}_3$$?

Accepted Answer

3-Methylpentane

Question 5

Which of the following best describes a primary (1°) carbon atom?

Accepted Answer

A carbon atom bonded to only one other carbon atom.

Question 6

What is the IUPAC name for the compound with the following condensed formula: $$\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3$$?

Accepted Answer

Pentane

Question 7

Which of the following statements about cycloalkanes is correct?

Accepted Answer

Cycloalkanes have the general formula $$\mathrm{C}_n\mathrm{H}_{2n}.$$

Question 8

Which conformation of cyclohexane is the most stable and why?

Accepted Answer

Chair conformation, because all bond angles are approximately $$109.5^\circ$$ and all bonds on adjacent carbons are staggered.

Question 9

Which of the following best explains why branched alkanes generally have lower boiling points than their straight-chain isomers?

Accepted Answer

Branched alkanes have smaller surface area, leading to weaker dispersion forces.

Question 10

Which of the following is the correct balanced equation for the complete combustion of propane ($$\mathrm{C}_3\mathrm{H}_8$$)?

Accepted Answer

$$\mathrm{C}_3\mathrm{H}_8 + 5\mathrm{O}_2 \longrightarrow 3\mathrm{CO}_2 + 4\mathrm{H}_2\mathrm{O}$$

Question 11

A molecule of 2,2,4-trimethylpentane is used as a standard in gasoline octane ratings. How many tertiary (3°) carbons are present in this molecule?

Accepted Answer

1

Question 12

Which of the following best describes the difference between a staggered and an eclipsed conformation in ethane?

Accepted Answer

In the staggered conformation, the hydrogen atoms on adjacent carbons are as far apart as possible, minimizing torsional strain.

Question 13

Which of the following is the correct IUPAC name for the compound shown below?

$$\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}(\mathrm{CH}_3)\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3$$

Accepted Answer

3-Methylhexane

Question 14

Which of the following is a correct statement about cis-trans isomerism in cycloalkanes?

Accepted Answer

Cis-trans isomers have the same molecular formula and connectivity but differ in the spatial arrangement of substituents.

Question 15

Which of the following best explains why cyclopentane adopts a puckered envelope conformation rather than remaining planar?

Accepted Answer

To reduce torsional strain from eclipsed C-H bonds.

Question 16

Which of the following is the correct IUPAC name for the compound with the structure below?

$$\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3$$

Accepted Answer

Hexane

Question 17

Which of the following is a correct statement about the physical properties of alkanes?

Accepted Answer

Alkanes are nonpolar and have only weak dispersion forces between molecules.

Question 18

Which of the following is the correct IUPAC name for a cycloalkane with two methyl groups on adjacent carbons of a cyclopentane ring, both on the same side?

Accepted Answer

cis-1,2-Dimethylcyclopentane

Question 19

Which of the following best describes the process of fractional distillation of petroleum?

Accepted Answer

It separates components based on their boiling points.

Alkanes and Cycloalkanes: Structure, Nomenclature, Conformations, and Properties

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