Question 1

Which of the following statements best describes resonance in organic molecules?

Accepted Answer

Resonance forms are interconverted by moving electrons only, not atoms.

Question 2

Which criterion is the MOST important when comparing resonance forms?

Accepted Answer

The resonance form with the most octets.

Question 3

What is the bond angle expected in a molecule where the central atom is $$sp^3$$ hybridized?

Accepted Answer

$$109.5^\circ$$

Question 4

Which of the following best describes the geometry and hybridization of the carbon atoms in ethylene ($$C_2H_4$$)?

Accepted Answer

Trigonal planar geometry, $$sp^2$$ hybridization

Question 5

Why can rotation occur around single bonds but not around double bonds in organic molecules?

Accepted Answer

Rotation around double bonds would break the $$\pi$$ bond formed by parallel overlap of p orbitals.

Question 6

Which of the following is NOT a functional group?

Accepted Answer

Isomer

Question 7

What is the correct line-angle (skeletal) representation for butane ($$C_4H_{10}$$)?

Accepted Answer

A zig-zag line with three vertices (two bends)

Question 8

Which of the following molecules contains a carbon atom with $$sp$$ hybridization?

Accepted Answer

Acetylene ($$C_2H_2)$$

Question 9

Which of the following is a constitutional (structural) isomer of butane ($$C_4H_{10}$$)?

Accepted Answer

2-methylpropane

Question 10

Which of the following best explains why the bond angle in methane ($$CH_4) is$$ $$109.5^\circ$$ instead of $$90^\circ$$?

Accepted Answer

The four valence orbitals of carbon hybridize to form four $$sp^3$$ orbitals, maximizing separation.

Question 11

Which of the following is true about geometric (cis/trans) isomers?

Accepted Answer

They differ in the orientation of groups around a double bond.

Question 12

Which of the following functional groups is present in acetonitrile ($$CH_3CN$$)?

Accepted Answer

Nitrile

Question 13

Which of the following best describes the difference between a $$\sigma$$ bond and a $$\pi$$ bond?

Accepted Answer

$$\sigma$$ bonds are formed by direct overlap of orbitals, while $$\pi$$ bonds are formed by parallel overlap of unhybridized p orbitals.

Question 14

Which of the following is a property of aromatic compounds?

Accepted Answer

They contain a benzene ring.

Question 15

Which of the following is NOT a reason why functional groups are important in organic chemistry?

Accepted Answer

They determine the molecular formula of a compound.

Question 16

A molecule has a central atom with two regions of electron density. What is the expected bond angle and hybridization?

Accepted Answer

$$180^\circ$$, sp$

Question 17

Which of the following best describes a constitutional isomer?

Accepted Answer

Compounds with the same molecular formula but different bonding sequences.

Question 18

Which of the following is a correct statement about the hydrogen molecule ($$H_2$$)?

Accepted Answer

The bond length is $$0.74\ 	ext{\AA}$$ and the bond dissociation energy is $$105\ 	ext{kcal/mol}.$$

Question 19

Which of the following best explains why $$sp^2$$ hybridized carbons have a bond angle of $$120^\circ$$?

Accepted Answer

Three $$sp^2$$ hybrid orbitals arrange themselves as far apart as possible in a trigonal planar geometry.

Chapter 1: Molecular Shapes, Resonance, Bond Rotation, and Isomerism

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