Q: Which of the following statements about molecular orbital (MO) theory for $\mathrm{O_2}$ is correct?

$\mathrm{O_2}$ is paramagnetic due to two unpaired electrons in the $\pi^*$ orbitals.

Q: A patient is exposed to carbon monoxide ($\mathrm{CO}$) poisoning. Which property of the CO molecule makes it especially dangerous in the body?

CO forms a very strong triple bond, making it stable and able to bind tightly to hemoglobin.

Q: Which of the following best explains why the bond angle in $\mathrm{H_2O}$ is less than $109.5^\circ$?

The presence of two lone pairs on oxygen increases electron repulsion, reducing the bond angle.

Q: Which of the following is the correct Lewis structure for $\mathrm{CO_2}$?

O=C=O, with each O atom having two lone pairs

Q: Which of the following statements about resonance is correct?

The actual structure is a hybrid of all valid resonance forms.

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

A $\sigma$ bond is stronger and results from end-to-end overlap, while a $\pi$ bond is weaker and results from side-to-side overlap.

Question 1

Which of the following molecules is expected to have the most polar bond, based on electronegativity differences?

Accepted Answer

HF (hydrogen fluoride)

Question 2

Which of the following correctly describes the trend in electronegativity across the periodic table?

Accepted Answer

Electronegativity decreases down a group and increases across a period.

Question 3

Which of the following molecules exhibits resonance?

Accepted Answer

O3

Question 4

What is the formal charge on the central atom in the Lewis structure of $\mathrm{NO_3^-}$ (nitrate ion)?

Accepted Answer

$+1$

Question 5

Which of the following molecules is an exception to the octet rule because it has fewer than 8 valence electrons on the central atom?

Accepted Answer

BF3

Question 6

Arrange the following bonds in order of increasing bond length: single bond, double bond, triple bond.

Accepted Answer

Triple < Double < Single

Question 7

What is the electron geometry and approximate bond angle of $\mathrm{NH_3}$ according to VSEPR theory?

Accepted Answer

Tetrahedral, $109.5^\circ$

Question 8

Which of the following molecules is polar, based on its molecular shape and bond polarity?

Accepted Answer

H2O

Question 9

What is the hybridization of the central atom in $\mathrm{SF_6}$?

Accepted Answer

$sp^3d^2$

Question 10

How many sigma ($\sigma$) and pi ($\pi$) bonds are present in the molecule $\mathrm{C_2H_2}$ (ethyne)?

Accepted Answer

3 $\sigma$, 2 $\pi$

Question 11

Which of the following statements about molecular orbital (MO) theory for $\mathrm{O_2}$ is correct?

Accepted Answer

$\mathrm{O_2}$ is paramagnetic due to two unpaired electrons in the $\pi^*$ orbitals.

Question 12

Calculate the bond order of $\mathrm{N_2}$ using molecular orbital theory.

Accepted Answer

3

Question 13

Which of the following diatomic species is predicted to be paramagnetic?

Accepted Answer

$\mathrm{O_2}$

Question 14

A patient is exposed to carbon monoxide ($\mathrm{CO}$) poisoning. Which property of the CO molecule makes it especially dangerous in the body?

Accepted Answer

CO forms a very strong triple bond, making it stable and able to bind tightly to hemoglobin.

Question 15

Which of the following molecules has a central atom with $sp^2$ hybridization?

Accepted Answer

BF3

Question 16

Which of the following best explains why the bond angle in $\mathrm{H_2O}$ is less than $109.5^\circ$?

Accepted Answer

The presence of two lone pairs on oxygen increases electron repulsion, reducing the bond angle.

Question 17

Which of the following is the correct Lewis structure for $\mathrm{CO_2}$?

Accepted Answer

O=C=O, with each O atom having two lone pairs

Question 18

Which of the following statements about resonance is correct?

Accepted Answer

The actual structure is a hybrid of all valid resonance forms.

Question 19

A molecule has the formula $\mathrm{AX_2E_2}$ (A = central atom, X = surrounding atoms, E = lone pairs). What is its molecular shape according to VSEPR theory?

Accepted Answer

Bent

Question 20

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

Accepted Answer

A $\sigma$ bond is stronger and results from end-to-end overlap, while a $\pi$ bond is weaker and results from side-to-side overlap.

Chemical Bonding: Lewis Structures, Molecular Shapes, and Bond Theories

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