Question 1

Which of the following statements best explains why carbon is uniquely suited to form the backbone of organic molecules?

Accepted Answer

Carbon is located in the middle of the second row of the periodic table, so it tends to share electrons rather than fully give up or accept them.

Question 2

Which of the following molecules contains a polar covalent bond?

Accepted Answer

$\mathrm{H-Cl}$

Question 3

A bond between which pair of atoms would you expect to have the largest dipole moment?

Accepted Answer

$\mathrm{H-F}$

Question 4

Which of the following best describes the relationship between bond length and bond strength?

Accepted Answer

As bond length decreases, bond strength increases.

Question 5

What is the formal charge on the nitrogen atom in the ammonium ion ($\mathrm{NH_4^+}$)?

Accepted Answer

$+1$

Question 6

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

Accepted Answer

The carbon atom uses $sp^3$ hybrid orbitals, which arrange themselves to minimize electron repulsion at $109.5^\circ$.

Question 7

Which of the following bonds has the greatest percentage of $s$ character?

Accepted Answer

$sp$ C-H bond

Question 8

A molecule of ethyne ($\mathrm{C_2H_2}$) has which of the following bond angles around each carbon atom?

Accepted Answer

$180^\circ$

Question 9

Which of the following statements about the polarity of bonds is correct?

Accepted Answer

A bond between two atoms with identical electronegativities is nonpolar.

Question 10

Which of the following best describes the electron configuration change that occurs when carbon forms four bonds in methane?

Accepted Answer

One $2s$ electron is promoted to a $2p$ orbital, and the resulting four orbitals hybridize to form four $sp^3$ orbitals.

Question 11

Which of the following best explains why the bond angle in water ($\mathrm{H_2O}$) is less than the ideal tetrahedral angle?

Accepted Answer

The presence of two lone pairs on oxygen compresses the bond angle to about $104.5^\circ$.

Question 12

Which of the following is the correct order of bond strength (from strongest to weakest) for the following carbon-carbon bonds: single, double, triple?

Accepted Answer

Triple > Double > Single

Question 13

Which of the following best describes the relationship between $s$ character and bond angle in hybrid orbitals?

Accepted Answer

As $s$ character increases, the bond angle increases.

Question 14

A molecule has a central atom with three regions of electron density and no lone pairs. What is the expected bond angle and hybridization of the central atom?

Accepted Answer

$120^\circ$ and $sp^2$

Question 15

Which of the following best explains why a C-F bond is more polar than a C-Cl bond?

Accepted Answer

Fluorine is more electronegative than chlorine, resulting in a greater difference in electronegativity with carbon.

Question 16

Which of the following is the correct formal charge on oxygen in the hydroxide ion ($\mathrm{OH^-}$)?

Accepted Answer

$-1$

Question 17

Which of the following best describes the bonding in ethene ($\mathrm{C_2H_4}$)?

Accepted Answer

Each carbon is $sp^2$ hybridized, forming three sigma bonds and one pi bond.

Question 18

Which of the following statements about lone pairs and bond angles is correct?

Accepted Answer

Lone pairs decrease the bond angle between atoms due to increased electron repulsion.

Question 19

Which of the following best describes the difference between ionic and covalent bonds?

Accepted Answer

Covalent bonds involve the sharing of electrons, while ionic bonds involve the transfer of electrons.

Chapter 1: Electronic Structure and Bonding – Foundations of Organic Chemistry

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