Question 1

Which of the following best describes the relationship between ethanol and diethyl ether, both with the molecular formula $$\mathrm{C_2H_6O}$$?

Accepted Answer

They are constitutional isomers.

Question 2

Given the bond-line formula for cyclopent-2-en-1-ol, which of the following is the correct expanded Lewis structure?

Accepted Answer

A structure with all carbons shown, each with enough hydrogens to satisfy the octet rule, and an -OH group attached to one carbon.

Question 3

Which rule must be followed when drawing resonance structures?

Accepted Answer

The total number of electrons must remain the same.

Question 4

Why are molecules with resonance generally more stable than those without?

Accepted Answer

Resonance allows for the delocalization of charge, reducing electron-electron repulsion.

Question 5

Which of the following is NOT a valid resonance structure for a molecule containing only second-row elements?

Accepted Answer

A structure where nitrogen has five bonds.

Question 6

Which resonance structure is generally the most important contributor to the resonance hybrid?

Accepted Answer

The one with the most covalent bonds and minimal separation of opposite charges.

Question 7

Which of the following compounds can have an expanded octet?

Accepted Answer

$$\mathrm{$$PCl_5$$}$$

Question 8

According to VSEPR theory, what is the molecular geometry of ammonia ($$\mathrm{NH_3$}$$)?

Accepted Answer

Trigonal pyramidal

Question 9

Which of the following statements about molecular dipole moments is correct?

Accepted Answer

A molecule with polar bonds can be nonpolar if the bond dipoles cancel out.

Question 10

Which of the following best explains why $$\mathrm{$$CCl_4$$} is $$nonpolar while $$\mathrm{CH_2Cl_2} is $$polar?

Accepted Answer

$$\mathrm{$$CCl_4$$}$$ has a symmetrical tetrahedral geometry, causing the bond dipoles to cancel.

Question 11

Which of the following is the most repulsive interaction according to VSEPR theory?

Accepted Answer

Unshared pair–unshared pair

Question 12

Which of the following is a constitutional isomer of 1-butanol ($$\mathrm{C_4H_{10}O}$$)?

Accepted Answer

Diethyl ether

Question 13

Which of the following is a correct statement about resonance hybrids?

Accepted Answer

The resonance hybrid is a weighted average of all valid resonance structures.

Question 14

Which of the following molecules has a linear molecular geometry?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 15

Which of the following is a valid resonance structure for the carbonate ion ($$\mathrm{CO_3$^{2-}}$$)?

Accepted Answer

A structure where the negative charge is delocalized over all three oxygen atoms.

Question 16

Which of the following best describes the effect of resonance on the bond lengths in ozone ($$\mathrm{O_3$}$$)?

Accepted Answer

Both O–O bonds are of equal length, intermediate between a single and double bond.

Question 17

Which of the following is true about the octet rule for third-row elements such as phosphorus and sulfur?

Accepted Answer

They can have more than eight electrons in their valence shell.

Question 18

Which of the following is the correct order of increasing repulsion between electron pairs according to VSEPR theory?

Accepted Answer

Bonded pair–bonded pair \u003c Unshared pair–bonded pair \u003c Unshared pair–unshared pair

Question 19

Which of the following is a correct statement about the molecular dipole moment of water ($$\mathrm{H_2O}$$)?

Accepted Answer

It is nonzero because the molecule is bent and the bond dipoles do not cancel.

Structural Formulas, Isomerism, Resonance, and Molecular Geometry in Organic Chemistry

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