Q: Which of the following is the correct formula for calculating the enthalpy change of a reaction using average bond enthalpies?

$$\Delta H_{rxn} = \sum \text{(bond enthalpies of bonds broken)} - \sum \text{(bond enthalpies of bonds formed)}$$

Question 1

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

Accepted Answer

Ionic bonding involves the transfer of electrons from one atom to another, resulting in the formation of ions, while covalent bonding involves the sharing of electrons between atoms.

Question 2

According to the octet rule, atoms tend to gain, lose, or share electrons until they are surrounded by how many valence electrons?

Accepted Answer

Eight

Question 3

Which of the following statements about lattice energy is correct?

Accepted Answer

Lattice energy increases with increasing charge and decreasing size of the ions.

Question 4

What is the formula for calculating the dipole moment ($$\mu) of a $$molecule?

Accepted Answer

$$\mu = Q 	imes r$$

Question 5

Which of the following molecules is an example of a compound with an expanded octet?

Accepted Answer

PF$$_5$$

Question 6

A student draws two possible Lewis structures for ozone (O$$_3). $$Both structures show different O–O bond orders. Experimental data shows both O–O bonds are identical. What concept explains this observation?

Accepted Answer

Resonance

Question 7

Which of the following is true regarding the bond strength and bond length of single, double, and triple covalent bonds?

Accepted Answer

Triple bonds are stronger and shorter than double bonds, which are stronger and shorter than single bonds.

Question 8

Which of the following best describes the electron configuration of ions formed by group 1 metals?

Accepted Answer

They lose electrons to achieve the configuration of the previous noble gas.

Question 9

Which of the following compounds is most likely to have ionic bonding based on electronegativity difference?

Accepted Answer

NaCl

Question 10

What is the formal charge on the central atom in the Lewis structure of PO$$_4$$^{3-}$$ (phosphate ion) if all oxygens are single-bonded to phosphorus?

Accepted Answer

+1

Question 11

Which of the following is NOT a basic type of chemical bond?

Accepted Answer

Hydrogen

Question 12

Which of the following best explains why ionic compounds tend to have high melting points?

Accepted Answer

They have strong electrostatic attractions between oppositely charged ions in a crystal lattice.

Question 13

Which of the following is the correct formula for calculating the enthalpy change of a reaction using average bond enthalpies?

Accepted Answer

$$\Delta H_{rxn} = \sum 	ext{(bond enthalpies of bonds broken)} - \sum 	ext{(bond enthalpies of bonds formed)}$$

Question 14

Which of the following elements is most likely to form compounds with less than an octet of electrons?

Accepted Answer

Boron

Question 15

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity increases from the bottom to the top of a group.

Question 16

Which of the following molecules contains a polar covalent bond?

Accepted Answer

HF

Question 17

A molecule has an odd number of valence electrons. Which of the following is most likely true?

Accepted Answer

It is likely to be highly reactive and unstable.

Question 18

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

Accepted Answer

Resonance structures are used when one Lewis structure cannot accurately depict the molecule.

Question 19

Which of the following is the dominant Lewis structure for a molecule?

Accepted Answer

The structure with formal charges closest to zero and negative charges on the most electronegative atoms.

Question 20

Which of the following best describes the bonding in metallic solids?

Accepted Answer

Free electrons hold metal atoms together.

Chapter 8: Basic Concepts of Chemical Bonding – Study Notes

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