Question 1

Which of the following molecules has the highest boiling point, and why?

A. $$\mathrm{CH_4$}

B$$. $$\mathrm{CH_3Cl}

C$$. $$\mathrm{CH_3OH}

D$$. $$\mathrm{C_2H_6}$$

Consider the types of intermolecular forces present in each molecule.

Accepted Answer

$$\mathrm{CH_3OH}$$, because it can form hydrogen bonds in addition to dipole-dipole and London dispersion forces.

Question 2

Which of the following statements best explains why $$\mathrm{NaCl} is a $$solid at room temperature while $$\mathrm{HCl} is a $$gas?

A. $$\mathrm{NaCl}$$ has a higher molecular weight than $$\mathrm{HCl}.

B$$. $$\mathrm{NaCl}$$ forms ionic bonds, while $$\mathrm{HCl}$$ forms covalent bonds.

C. $$\mathrm{NaCl}$$ has stronger London dispersion forces than $$\mathrm{HCl}.

D$$. $$\mathrm{NaCl} is $$more polar than $$\mathrm{HCl}.$$

Accepted Answer

$$\mathrm{NaCl}$$ forms ionic bonds, while $$\mathrm{HCl}$$ forms covalent bonds.

Question 3

A compound has a molecular ion peak at $$m/z = 58 in $$its mass spectrum and shows a strong IR absorption at $$1715\ \mathrm{cm}^{-1}. $$Which of the following is the most likely structure?

A. $$\mathrm{C_3H_6O} ($$propanal)

B. $$\mathrm{C_3H_6O} ($$acetone)

C. $$\mathrm{C_2H_6O} ($$ethanol)

D. $$\mathrm{C_4H_{10}} ($$butane)

Accepted Answer

$$\mathrm{C_3H_6O} ($$acetone)

Question 4

Which of the following bonds would you expect to have the highest IR stretching frequency?

A. $$\mathrm{C-H}

B$$. $$\mathrm{C=O}

C$$. $$\mathrm{C\equiv C}

D$$. $$\mathrm{C-O}$$

Accepted Answer

$$\mathrm{C-H}$$

Question 5

Which of the following statements about electronegativity is correct?

A. Electronegativity increases down a group and decreases across a period.

B. Electronegativity decreases down a group and increases across a period.

C. Electronegativity is the same for all elements in a period.

D. Electronegativity is highest for alkali metals.

Accepted Answer

Electronegativity decreases down a group and increases across a period.

Question 6

Which of the following is the best nucleophile in a polar protic solvent?

A. $$\mathrm{F^-}

B$$. $$\mathrm{Cl^-}

C$$. $$\mathrm{Br^-}

D$$. $$\mathrm{I^-}$$

Accepted Answer

$$\mathrm{I^-}$$

Question 7

Which of the following statements about resonance structures is TRUE?

A. Resonance structures represent different compounds in equilibrium.

B. The actual molecule is best represented by the most stable resonance structure only.

C. Resonance structures differ only in the placement of electrons, not atoms.

D. Resonance structures must have different molecular formulas.

Accepted Answer

Resonance structures differ only in the placement of electrons, not atoms.

Question 8

Which of the following compounds is the strongest acid?

A. $$\mathrm{CH_4$}

B$$. $$\mathrm{NH_3$}

C$$. $$\mathrm{H_2O}

D$$. $$\mathrm{HF}$$

Accepted Answer

$$\mathrm{HF}$$

Question 9

A molecule has the following IR absorptions: $$3300\ \mathrm{cm}^{-1} ($$broad), $$2100\ \mathrm{cm}^{-1} ($$medium), and $$1600\ \mathrm{cm}^{-1} ($$weak). Which functional group is most likely present?

A. Alcohol

B. Alkyne

C. Alkene

D. Ketone

Accepted Answer

Alkyne

Question 10

Which of the following best explains why $$\mathrm{NH_3$} is a $$stronger base than $$\mathrm{H_2O}$$?

A. Nitrogen is less electronegative than oxygen, so it holds its lone pair less tightly and is more willing to share it.

B. Nitrogen is more electronegative than oxygen, so it is more basic.

C. $$\mathrm{NH_3$}$$ has more lone pairs than $$\mathrm{H_2O}.

D$$. $$\mathrm{NH_3$} is a $$gas at room temperature.

Accepted Answer

Nitrogen is less electronegative than oxygen, so it holds its lone pair less tightly and is more willing to share it.

Question 11

Which of the following is the correct order of increasing acidity?

A. $$\mathrm{CH_4$} \u003c \mathrm{NH_3$} \u003c \mathrm{H_2O} \u003c \mathrm{HF}

B$$. $$\mathrm{HF} \u003c \mathrm{H_2O} \u003c \mathrm{NH_3$} \u003c \mathrm{CH_4$}

C$$. $$\mathrm{NH_3$} \u003c \mathrm{CH_4$} \u003c \mathrm{H_2O} \u003c \mathrm{HF}

D$$. $$\mathrm{CH_4$} \u003c \mathrm{H_2O} \u003c \mathrm{NH_3$} \u003c \mathrm{HF}$$

Accepted Answer

$$\mathrm{CH_4$} \u003c \mathrm{NH_3$} \u003c \mathrm{H_2O} \u003c \mathrm{HF}$$

Question 12

Which of the following best describes the hybridization of the central atom in $$\mathrm{CO_2$}$$?

A. $$\mathrm{sp^3$}

B$$. $$\mathrm{sp^2$}

C$$. $$\mathrm{sp}

D$$. $$\mathrm{$$dsp^2$$}$$

Accepted Answer

$$\mathrm{sp}$$

Question 13

A molecule has a molecular formula of $$\mathrm{C_4H_8O}$$ and shows a strong IR absorption at $$1720\ \mathrm{cm}^{-1}. $$Which functional group is most likely present?

A. Alcohol

B. Ether

C. Ketone

D. Alkene

Accepted Answer

Ketone

Question 14

Which of the following best explains why $$\mathrm{HCl} is a $$stronger acid than $$\mathrm{HF}$$, even though fluorine is more electronegative than chlorine?

A. $$\mathrm{HCl}$$ has a weaker H–Cl bond, making it easier to ionize.

B. $$\mathrm{HCl} is $$more polar than $$\mathrm{HF}.

C$$. $$\mathrm{HCl}$$ has a higher molecular weight.

D. $$\mathrm{HCl}$$ forms stronger hydrogen bonds.

Accepted Answer

$$\mathrm{HCl}$$ has a weaker H–Cl bond, making it easier to ionize.

Question 15

Which of the following is the best description of a Lewis acid?

A. A substance that donates a proton.

B. A substance that accepts a pair of electrons.

C. A substance that donates a pair of electrons.

D. A substance that accepts a proton.

Accepted Answer

A substance that accepts a pair of electrons.

Question 16

Which of the following statements about molecular polarity is correct?

A. A molecule with polar bonds is always polar.

B. A molecule with nonpolar bonds can never be polar.

C. The geometry of a molecule can cause polar bonds to cancel, resulting in a nonpolar molecule.

D. The presence of lone pairs always makes a molecule polar.

Accepted Answer

The geometry of a molecule can cause polar bonds to cancel, resulting in a nonpolar molecule.

Question 17

Which of the following is the correct electron configuration for the carbon atom in its ground state?

A. $$1s^2$$\ $$2s^2$$\ $$2p^2

B$$. $$1s^2$$\ $$2s^1$$\ $$2p^3

C$$. $$1s^2$$\ $$2s^2$$\ $$2p^4

D$$. $$1s^2$$\ $$2s^2$$\ $$2p^6$$

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^2$$

Question 18

A compound with the formula $$\mathrm{C_2H_5Br} is $$treated with $$\mathrm{NaOH} in $$water. Which of the following is the major product?

A. $$\mathrm{C_2H_6}

B$$. $$\mathrm{C_2H_5OH}

C$$. $$\mathrm{C_2H_4}

D$$. $$\mathrm{C_2H_5ONa}$$

Accepted Answer

$$\mathrm{C_2H_5OH}$$

Question 19

Which of the following best explains why $$\mathrm{CO_2$} is $$nonpolar, even though it contains polar bonds?

A. The molecule is linear, so the dipoles cancel each other out.

B. The molecule is bent, so the dipoles reinforce each other.

C. The $$\mathrm{C=O}$$ bonds are nonpolar.

D. $$\mathrm{CO_2$}$$ has no lone pairs on the central atom.

Accepted Answer

The molecule is linear, so the dipoles cancel each other out.

Question 20

A mass spectrum of a compound shows a molecular ion peak at $$m/z = 78$$ and a base peak at $$m/z = 77. $$The IR spectrum shows strong absorption at $$1600\ \mathrm{cm}^{-1}$$ and $$3030\ \mathrm{cm}^{-1}. $$Which compound is most likely present?

A. Benzene

B. Cyclohexane

C. Toluene

D. Phenol

Accepted Answer

Benzene

Organic Chemistry Exam Study Guide: Atomic Structure, Molecular Properties, Resonance, Acidity, and Spectroscopy

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