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 \u003c Double \u003c 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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