Question 1

Which of the following best explains why morphine can mimic the effects of endorphins in the human body?

Accepted Answer

Morphine has a similar molecular shape to endorphins, allowing it to bind to the same pain receptors.

Question 2

Which of the following bonds is best described as ionic based on the difference in electronegativity ($$\Delta EN$$)?

Accepted Answer

The bond in $$\mathrm{AlF}$$, where $$\Delta EN = 2.5$$

Question 3

Which of the following statements about resonance structures is correct?

Accepted Answer

Resonance structures represent different possible arrangements of electrons, and the true structure is a hybrid of these forms.

Question 4

Which of the following molecules is an example of a species with an incomplete octet?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 5

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

Accepted Answer

As bond length decreases, bond energy increases.

Question 6

A molecule has four electron groups around its central atom, one of which is a lone pair. What is the molecular geometry and approximate bond angle?

Accepted Answer

Trigonal pyramidal, $$\approx 107$$^{\circ}$$

Question 7

Which of the following is the correct procedure for predicting the molecular geometry of a molecule using VSEPR theory?

Accepted Answer

Draw the Lewis structure, count the number of electron groups on the central atom, determine the number of bonding groups and lone pairs, and use this information to identify the electron and molecular geometry.

Question 8

Which of the following molecules is predicted to have a net dipole moment?

Accepted Answer

$$\mathrm{H_2O}$$

Question 9

Given the following average bond energies: $$\mathrm{C-H}$$: $$413\ \mathrm{kJ/mol}$$, $$\mathrm{O=O}$$: $$495\ \mathrm{kJ/mol}$$, $$\mathrm{C=O}$$: $$799\ \mathrm{kJ/mol}$$, calculate the approximate enthalpy change ($$\Delta H_{rxn}) $$for the combustion of methane: $$\mathrm{CH_4$} + 2\ \mathrm{O_2$} \rightarrow \mathrm{CO_2$} + 2\ \mathrm{H_2O}.$$

Accepted Answer

$$-802\ \mathrm{kJ/mol}$$

Question 10

Which of the following is NOT a valid reason why second-period elements (such as carbon, nitrogen, and oxygen) cannot have expanded octets?

Accepted Answer

They have higher electronegativity than third-period elements.

Question 11

Which of the following correctly describes the effect of lone pairs on molecular geometry and bond angles?

Accepted Answer

Lone pairs occupy more space than bonding pairs, causing bond angles to decrease compared to the ideal geometry.

Question 12

Which of the following molecules or ions requires drawing resonance structures to accurately represent its bonding?

Accepted Answer

$$\mathrm{NO_2$^-}$$

Question 13

A molecule has five electron groups around the central atom, two of which are lone pairs. What is the molecular geometry?

Accepted Answer

T-shaped

Question 14

Which of the following best describes the polarity of $$\mathrm{CO_2$}$$?

Accepted Answer

The molecule has polar bonds but is nonpolar overall due to its linear geometry.

Question 15

Which of the following is the correct formula for calculating the dipole moment ($$\mu) of a $$bond?

Accepted Answer

$$\mu = q 	imes r$$

Question 16

Which of the following is a correct Lewis structure for $$\mathrm{CS_2$}$$?

Accepted Answer

A central carbon atom double bonded to each sulfur atom, with each sulfur atom having two lone pairs.

Question 17

Which of the following molecules has an expanded octet on the central atom?

Accepted Answer

$$\mathrm{SF_6$}$$

Question 18

Which of the following best explains why water and oil are immiscible?

Accepted Answer

Water is polar and oil is nonpolar, so their molecules do not mix due to differences in molecular polarity.

Question 19

Which of the following is the correct formal charge on the nitrogen atom in the Lewis structure of $$\mathrm{NO_2$^-}$$, where nitrogen forms one single bond and one double bond with oxygen atoms and has no lone pairs?

Accepted Answer

0

Chemical Bonding I: Lewis Structures and Molecular Shapes

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