Structural formula quiz worksheet with questions on identifying correct molecular representations.

Problem Analysis and Solution

The provided worksheet contains three questions related to structural formulas in chemistry. Let's solve each question step by step.

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#### Question 1: Which of the following shows the correct condensed structural formula of a compound that has five carbon (C) atoms, 12 hydrogen (H) atoms, and one oxygen (O) atom?

Given Information:
- The compound has:
- 5 carbon (C) atoms
- 12 hydrogen (H) atoms
- 1 oxygen (O) atom

Task:
Identify the correct condensed structural formula from the given options.

Analysis:
1. Condensed Structural Formula: This is a shorthand way of writing the molecular structure where carbon chains are written in a linear fashion, and functional groups are explicitly shown.
2. The molecular formula for the compound can be derived as \( C_5H_{12}O \).
3. We need to check each option to see if it matches the given molecular formula and structure.

Options:
- Option A:
\[
\text{CH}_3\text{CH(CH}_3\text{)CH}_2\text{COH}
\]
- This formula indicates:
- 1 methyl group (\(\text{CH}_3\))
- 1 ethyl group (\(\text{CH}_2\text{CH}_3\))
- 1 carboxylic acid group (\(\text{COH}\))
- Counting atoms:
- Carbon: \(1 + 1 + 3 = 5\)
- Hydrogen: \(3 + 5 + 1 = 9\) (incorrect, should be 12)
- Oxygen: \(1\)
- Incorrect because it does not have 12 hydrogen atoms.

- Option B:
\[
\text{CH}_3\text{CH(CH}_3\text{)}_2\text{COH}
\]
- This formula indicates:
- 1 methyl group (\(\text{CH}_3\))
- 2 isopropyl groups (\(\text{CH(CH}_3\text{)}_2\))
- 1 carboxylic acid group (\(\text{COH}\))
- Counting atoms:
- Carbon: \(1 + 2 \times 3 = 7\) (incorrect, should be 5)
- Hydrogen: \(3 + 2 \times 7 + 1 = 18\) (incorrect, should be 12)
- Oxygen: \(1\)
- Incorrect because it has too many carbon and hydrogen atoms.

- Option C:
\[
\text{CH}_3\text{CH(CH}_3\text{)CH}_2\text{OH}
\]
- This formula indicates:
- 1 methyl group (\(\text{CH}_3\))
- 1 ethyl group (\(\text{CH}_2\text{CH}_3\))
- 1 alcohol group (\(\text{OH}\))
- Counting atoms:
- Carbon: \(1 + 1 + 3 = 5\)
- Hydrogen: \(3 + 5 + 1 = 9\) (incorrect, should be 12)
- Oxygen: \(1\)
- Incorrect because it does not have 12 hydrogen atoms.

- Option D:
\[
\text{CH}_3\text{C(CH}_3\text{)}_2\text{COH}
\]
- This formula indicates:
- 1 methyl group (\(\text{CH}_3\))
- 2 tert-butyl groups (\(\text{C(CH}_3\text{)}_2\))
- 1 carboxylic acid group (\(\text{COH}\))
- Counting atoms:
- Carbon: \(1 + 3 = 4\) (incorrect, should be 5)
- Hydrogen: \(3 + 9 + 1 = 13\) (incorrect, should be 12)
- Oxygen: \(1\)
- Incorrect because it does not have the correct number of carbon and hydrogen atoms.

- Correct Answer:
Upon re-evaluating the options, the correct formula should be:
\[
\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{CH}_2\text{OH}
\]
- This formula indicates a straight-chain pentanol.
- Counting atoms:
- Carbon: \(5\)
- Hydrogen: \(12\)
- Oxygen: \(1\)
- This matches the given molecular formula \( C_5H_{12}O \).

Final Answer for Question 1:
\[
\boxed{\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{CH}_2\text{OH}}
\]

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#### Question 2: Which of the following is the correct skeletal structural formula for the following compound?

Given Compound:
\[
\text{H}_3\text{C-CH}_2\text{-CH}_2\text{-CH}_2\text{-CO-CH}_2\text{-CH}_3
\]

Task:
Identify the correct skeletal structural formula from the given options.

Analysis:
1. Skeletal Structural Formula: In this format, carbon chains are represented by lines, and carbon atoms are implied at the ends and intersections of the lines. Hydrogen atoms are not shown explicitly unless they are part of a functional group.
2. The given compound is a heptane derivative with a ketone group (\(\text{CO}\)).

Options:
- Option A:
\[
\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{COCH}_3
\]
- This is the condensed formula, not the skeletal formula.
- Incorrect because it is not in skeletal format.

- Option B:
\[
\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{COCH}_3
\]
- This is the condensed formula, not the skeletal formula.
- Incorrect because it is not in skeletal format.

- Option C:
\[
\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{COCH}_3
\]
- This is the condensed formula, not the skeletal formula.
- Incorrect because it is not in skeletal format.

- Option D:
\[
\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{COCH}_3
\]
- This is the condensed formula, not the skeletal formula.
- Incorrect because it is not in skeletal format.

- Correct Answer:
The correct skeletal formula should be:
\[
\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{COCH}_3
\]
- In skeletal format, this would be represented as:
```
CH3-CH2-CH2-CH2-C=O-CH2-CH3
```

Final Answer for Question 2:
\[
\boxed{\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{COCH}_3}
\]

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#### Question 3: What is the correct line-bond structural formula for the compound shown below?

Given Compound:
\[
\text{H : C : O : H}
\]

Task:
Identify the correct line-bond structural formula from the given options.

Analysis:
1. Line-Bond Structural Formula: This format shows all atoms and bonds explicitly.
2. The given compound is methanol (\(\text{CH}_3\text{OH}\)).

Options:
- Option A:
\[
\text{H : C : O : H}
\]
- This is the Lewis structure, not the line-bond formula.
- Incorrect because it is not in line-bond format.

- Option B:
\[
\text{H-C-O-H}
\]
- This is the line-bond formula for methanol.
- Correct because it shows all atoms and bonds explicitly.

- Option C:
\[
\text{H-C-O-H}
\]
- This is the line-bond formula for methanol.
- Correct because it shows all atoms and bonds explicitly.

- Option D:
\[
\text{H-C-O-H}
\]
- This is the line-bond formula for methanol.
- Correct because it shows all atoms and bonds explicitly.

- Option E:
\[
\text{CH}_3\text{-O-H}
\]
- This is the condensed formula, not the line-bond formula.
- Incorrect because it is not in line-bond format.

Final Answer for Question 3:
\[
\boxed{\text{H-C-O-H}}
\]

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Final Answers:

1. \(\boxed{\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{CH}_2\text{OH}}\)
2. \(\boxed{\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{COCH}_3}\)
3. \(\boxed{\text{H-C-O-H}}\)