Question 1

Draw the Lewis structure for CO₃^2- including any valid resonance structures.Which of the following statements is TRUE?

Accepted Answer

According to the Lewis structure, there is one C-O single bond and one C-O double bond in the CO₃^2- ion. The double bond can delocalize onto the sulfur atom to form a resonance structure with two C-O single bonds, but that does not change the fact that there is only one C-O double bond in the compound. Therefore, choice B is the correct answer. The other choices either have too many or too few C-O bonds compared to the actual compound.

Question 2

Place the following in order of decreasing bond length. H-F H-I H-Br

Accepted Answer

Bond length generally increases as atomic size increases. Therefore, H-I will have the longest bond length, followed by H-Br, and then H-F. Therefore, the correct answer is choice C.

Question 3

Rank the following molecules in decreasing bond energy. Cl₂ Br₂ F₂ I₂

Accepted Answer

Bond energy generally decreases as you move down a group in the periodic table due to increasing atomic size and the corresponding increase in bond length. Therefore, the bond energy of halogens with another atom decreases in the order F > Cl > Br > I, making option B correct.

Question 4

Draw the best Lewis structure for Cl₃⁻.What is the formal charge on the central Cl atom?

Accepted Answer

The central Cl atom has a formal charge of -1 because it has three bonding pairs and one lone pair of electrons.

Question 5

Place the following in order of increasing bond length. C-O C-C C-N

Accepted Answer

Bond length is inversely related to bond strength and bond order. C-O has the shortest bond length due to the double bond character in many compounds, followed by C-N, and C-C has the longest bond length as it is typically a single bond.

Question 6

Which compound has the shortest carbon-carbon bond length?

Accepted Answer

HCCH, or ethyne, has a triple bond between the carbons, which is shorter than a double or single bond. Therefore, it has the shortest carbon-carbon bond length out of the given compounds.

Question 7

Using Lewis structures and formal charge,which of the following ions is most stable,? OCN⁻ ONC⁻ NOC⁻

Accepted Answer

In Lewis structures, the most stable ion is the one that has the lowest formal charge. 
OCN⁻ has the most stable Lewis structure because the formal charges on each atom is the lowest (0, -1, +1) compared to the other ions. ONC⁻ has formal charges of (+1, -1, 0) and NOC⁻ has formal charges of (-1, +1, 0), which makes them less stable. Therefore, OCN⁻ is the most stable ion according to Lewis theory.

Question 8

Which of the following resonance structures for OCN⁻ will contribute most to the correct structure of OCN⁻?

Accepted Answer

The answer of Which of the following resonance structures for...

Question 9

Choose the best Lewis structure for NH₄⁺.

Accepted Answer

The answer of Choose the best Lewis structure for NH₄⁺. ...

Question 10

Identify the bond with the highest bond energy.

Accepted Answer

The answer of Identify the bond with the highest bond...

Question 11

Define bond energy.

Accepted Answer

Bond energy is the amount of energy required to break 1 mole of the bond in the gas phase. This is because in the gas phase, the bonds are not influenced by intermolecular forces or the structure of the solid or liquid phase.

Question 12

Place the following in order of decreasing XO bond length,where "X" represents the central atom in each of the following compounds or ions. SiO₃²⁻ CO₂ CO₃²⁻

Accepted Answer

The bond length in these compounds is influenced by the size of the central atom and the presence of double or triple bonds. Silicon (Si) is larger than carbon (C), leading to a longer Si-O bond compared to C-O bonds. Between the CO compounds, the one with a triple bond (C≡O) has a shorter bond length than the one with a double bond (C=O) due to the stronger, shorter triple bond.

Question 13

The Lewis structure of sulfuric acid contains

Accepted Answer

Sulfuric acid (H2SO4) has a Lewis structure with 2 double bonds between sulfur and oxygen, 4 single bonds (2 between sulfur and oxygen, and 2 between oxygen and hydrogen), and 8 lone pairs on the oxygen atoms.

Question 14

Which compound has the highest carbon-carbon bond strength?

Accepted Answer

HCCH, also known as ethyne or acetylene, has a triple bond between the two carbon atoms, which is the strongest type of carbon-carbon bond. The compounds in choices A and B have double bonds, which are weaker than triple bonds. Therefore, choice C has the highest carbon-carbon bond strength. Choice D is incorrect, as not all bond strengths are the same.

Question 15

How many electrons does an hydroxyl radical contain?

Accepted Answer

The hydroxyl radical has 7 electrons. It is a free radical, meaning it has an unpaired electron. The hydroxyl radical is a highly reactive species that can damage cells and DNA.

Question 16

Place the following in order of increasing bond length. NO₂⁻ NO₃⁻ NO

Accepted Answer

The bond length is inversely related to bond order. NO has the highest bond order (2.5), followed by NO₂⁻ (1.5), and NO₃⁻ has the lowest (1.33). Thus, NO has the shortest bond length, followed by NO₂⁻, and NO₃⁻ has the longest.

Question 17

Draw the Lewis structure for NO₂⁻ including any valid resonance structures.Describe the resonance hybrid of the nitrite ion.

Accepted Answer

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Question 18

A reaction is exothermic when

Accepted Answer

Exothermic reactions release energy, which means that the products have lower energy than the reactants. This occurs when weak bonds break and strong bonds form, as the energy released from the formation of the strong bonds is greater than the energy required to break the weak bonds. Therefore, choice A is the best option.

Question 19

Draw the Lewis structure for SO₄²⁻.How many equivalent resonance structures can be drawn?

Accepted Answer

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Question 20

Which compound has the longest carbon-carbon bond length?

Accepted Answer

The answer of Which compound has the longest carbon-carbon bond...

Quiz 9: Chemical Bonding I: Lewis Theory

Draw the Lewis structure for CO32- including any valid resonance structures.Which of the following statements is TRUE?