Q: Which of the following is the correct formula to estimate the enthalpy change of a reaction using bond energies?

$$\Delta H_{\text{rxn}} = \sum (\Delta H_{\text{bonds broken}}) + \sum (\Delta H_{\text{bonds formed}})$$

Question 1

Which of the following best explains why heroin can mimic the action of endorphins in the human body?

Accepted Answer

Heroin has a similar molecular shape to endorphins, allowing it to bind to opioid receptors.

Question 2

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity is the ability of an atom in a molecule to attract electrons to itself.

Question 3

Arrange the following elements in order of decreasing electronegativity: Si, F, O, C.

Accepted Answer

F \u003e O \u003e C \u003e Si

Question 4

Which bond is most likely to be ionic based on electronegativity difference?

Accepted Answer

Cs-Cl

Question 5

What is the dipole moment ($$\mu) $$formula for a bond?

Accepted Answer

$$\mu = (q)(r)$$

Question 6

Which molecule has a net dipole moment of zero?

Accepted Answer

CO$$_2$$

Question 7

What is the correct Lewis structure for ammonia (NH$$_3$$)?

Accepted Answer

A nitrogen atom with three single bonds to hydrogen atoms and one lone pair on nitrogen.

Question 8

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

Accepted Answer

Resonance structures have the same connectivity but differ in the arrangement of electrons.

Question 9

Calculate the formal charge on the sulfur atom in SO$$_2$$ for the following Lewis structure: O=S–O, where the left O has two lone pairs, S has one lone pair, and the right O has three lone pairs.

Accepted Answer

$$+1$$

Question 10

Which of the following molecules is an example of an expanded octet?

Accepted Answer

SF$$_6$$

Question 11

Which of the following best describes the bond energy trend for single, double, and triple bonds between carbon atoms?

Accepted Answer

$$\mathrm{C \equiv C} \u003e \mathrm{C = C} \u003e \mathrm{C - C}$$

Question 12

Which of the following molecules has a tetrahedral electron geometry?

Accepted Answer

CH$$_4$$

Question 13

What is the bond angle in a molecule with trigonal planar electron geometry?

Accepted Answer

$$120^\circ$$

Question 14

Which of the following statements about lone pairs is correct according to VSEPR theory?

Accepted Answer

Lone pairs occupy more space on the central atom than bonding pairs.

Question 15

Which of the following molecules is polar due to its molecular geometry?

Accepted Answer

H$$_2O$$

Question 16

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

Accepted Answer

Trigonal pyramidal

Question 17

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

Accepted Answer

Shorter bonds are generally stronger than longer bonds.

Question 18

Which of the following is the correct formula to estimate the enthalpy change of a reaction using bond energies?

Accepted Answer

$$\Delta H_{	ext{rxn}} = \sum (\Delta H_{	ext{bonds broken}}) + \sum (\Delta H_{	ext{bonds formed}})$$

Question 19

Which of the following is an exception to the octet rule?

Accepted Answer

NO (nitric oxide)

Chapter 5: Chemical Bonding I – Lewis Structures, Molecular Shapes, and Bond Properties

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