Rucete ✏ Campbell Biology In a Nutshell
Unit 1 THE CHEMISTRY OF LIFE — Concept 4.2 Carbon Atoms Can Form Diverse Molecules by Bonding to Four Other Atoms — Practice Questions
(Multiple Choice — Click to Reveal Answer)
1. How many valence electrons does a carbon atom have?
- 2
- 4
- 6
- 8
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2. 4
2. What shape is a molecule when carbon forms four single bonds?
- Linear
- Planar
- Tetrahedral
- Hexagonal
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3. Tetrahedral
3. What type of bond does carbon typically form?
- Ionic
- Covalent
- Metallic
- Hydrogen
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2. Covalent
4. In a molecule with a double bond, what shape do atoms around carbon lie in?
- Tetrahedral
- Planar
- Linear
- Octahedral
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2. Planar
5. Which molecule is flat due to a carbon–carbon double bond?
- CH₄
- C₂H₄
- C₂H₆
- CO₂
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2. C₂H₄
6. What angle do bonds form in a tetrahedral molecule?
- 90°
- 109.5°
- 120°
- 180°
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2. 109.5°
7. Which element commonly forms four bonds in organic molecules?
- Hydrogen
- Oxygen
- Carbon
- Nitrogen
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3. Carbon
8. What is the molecular formula of ethane?
- C₂H₂
- C₂H₄
- C₂H₆
- C₂H₈
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3. C₂H₆
9. What kind of bonds are present in carbon dioxide (CO₂)?
- Single
- Double
- Triple
- Ionic
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2. Double
10. What makes hydrocarbons hydrophobic?
- They are ionic
- They are polar
- They are nonpolar
- They contain nitrogen
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3. They are nonpolar
11. What is a hydrocarbon?
- A molecule with carbon, oxygen, and nitrogen
- Only carbon and hydrogen
- A type of protein
- An ion
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2. Only carbon and hydrogen
12. What makes carbon versatile in bonding?
- Its size
- Its four valence electrons
- Its polarity
- Its low electronegativity
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2. Its four valence electrons
13. Which of the following is NOT a type of isomer?
- Structural
- Cis-trans
- Enantiomer
- Isobar
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4. Isobar
14. Which type of isomer has mirror-image forms?
- Structural
- Cis-trans
- Enantiomer
- Radical
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3. Enantiomer
15. What determines the shape of a molecule?
- Electronegativity
- Bond angles
- Molecular weight
- Hydrogen bonds
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2. Bond angles
16. What does each line in a structural formula represent?
- A lone pair
- A shared electron pair
- A polar bond
- A hydrogen bond
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2. A shared electron pair
17. What causes cis-trans isomers to differ?
- Free rotation around single bonds
- Rigid double bonds
- Hydrogen bonding
- Size of atoms
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2. Rigid double bonds
18. How many covalent bonds does nitrogen usually form?
- 1
- 2
- 3
- 4
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3. 3
19. What is the molecular formula of propane?
- C₂H₆
- C₃H₈
- C₄H₁₀
- C₃H₆
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2. C₃H₈
20. What are structural isomers?
- Same bonds, different angles
- Different arrangements of atoms
- Opposite charges
- Same properties
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2. Different arrangements of atoms
21. What is the common characteristic of all hydrocarbons?
- They contain oxygen
- They are hydrophilic
- They contain only carbon and hydrogen
- They are charged
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3. They contain only carbon and hydrogen
22. Why is carbon dioxide considered inorganic by some definitions?
- It has no carbon
- It has no hydrogen
- It’s too reactive
- It’s a gas
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2. It has no hydrogen
23. Which molecule is an enantiomer used as a medication?
- Water
- Oxygen
- Albuterol
- Carbon dioxide
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3. Albuterol
24. What distinguishes enantiomers from each other?
- Charge
- Mass
- Mirror-image structure
- Atomic number
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3. Mirror-image structure
25. What shape do overlapping tetrahedrons represent?
- Ethane
- Urea
- Methane
- CO₂
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1. Ethane
26. Why can't atoms freely rotate around a double bond?
- Because they are too large
- Because double bonds are shorter
- Because pi bonds prevent rotation
- Because they are unstable
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3. Because pi bonds prevent rotation
27. What feature makes carbon ideal for building large complex molecules?
- Low reactivity
- Ability to form four stable covalent bonds
- High polarity
- Hydrophobicity
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2. Ability to form four stable covalent bonds
28. In ethene (C₂H₄), how many sigma and pi bonds are there between the two carbon atoms?
- 1 sigma, 1 pi
- 2 sigma
- 1 sigma, 2 pi
- 1 pi only
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1. 1 sigma, 1 pi
29. What causes the difference in biological activity between drug enantiomers?
- Different bonding energies
- Different solubilities
- Different 3D shapes interacting with receptors
- Different electron configurations
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3. Different 3D shapes interacting with receptors
30. Which pair are structural isomers?
- cis-butene and trans-butene
- pentane and 2-methylbutane
- L-alanine and D-alanine
- methane and ethane
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2. pentane and 2-methylbutane
31. Which type of isomer arises from an asymmetric carbon?
- Cis-trans isomer
- Structural isomer
- Enantiomer
- Geometric isomer
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3. Enantiomer
32. What is the biological significance of molecular shape?
- It has no effect on interactions
- Only affects solubility
- It determines how molecules recognize and respond to each other
- It only affects gases
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3. It determines how molecules recognize and respond to each other
33. How does CO₂ differ from methane in shape and bonding?
- CO₂ is tetrahedral; CH₄ is linear
- CO₂ is linear with double bonds; CH₄ is tetrahedral with single bonds
- Both are tetrahedral
- Both are linear
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2. CO₂ is linear with double bonds; CH₄ is tetrahedral with single bonds
34. What structural feature of benzene makes it unique?
- It has alternating single and double bonds
- It has a linear carbon skeleton
- It forms ionic bonds
- It lacks hydrogen
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1. It has alternating single and double bonds
35. Which molecule below contains a carbon skeleton in ring form?
- C₂H₆
- CH₄
- Cyclohexane
- Ethene
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3. Cyclohexane
36. Explain why carbon atoms can form such a large variety of molecules.
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Because carbon can form four covalent bonds with various atoms, including itself, allowing diverse structures like chains, rings, and branches.
37. What is the difference between a cis isomer and a trans isomer?
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Cis isomers have substituents on the same side of a double bond, while trans isomers have them on opposite sides.
38. How do enantiomers affect drug effectiveness?
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Only one enantiomer may fit the target receptor in the body, making the other ineffective or even harmful.
39. Describe the geometry of methane and explain why it forms that shape.
Show Answer
Methane is tetrahedral due to repulsion between electron pairs around the central carbon.
40. Why are hydrocarbons considered nonpolar?
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Because the C-H bonds have similar electronegativities, resulting in even distribution of charge.
41. What makes CO₂ a linear molecule?
Show Answer
The two double bonds from carbon to oxygen repel each other equally, forming a 180° angle.
42. Why don’t double bonds rotate freely?
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Because the pi bond locks the atoms in place, preventing rotation.
43. What are the three types of isomers discussed in Concept 4.2?
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Structural isomers, cis-trans isomers, and enantiomers.
44. How does carbon bonding contribute to life's complexity?
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It enables the formation of complex macromolecules like proteins, nucleic acids, and carbohydrates.
45. What is the difference between ethane and ethene in terms of bonding?
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Ethane has a single bond between carbon atoms; ethene has a double bond.
46. Describe how molecular shape affects biological function.
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The shape determines whether a molecule can bind to a receptor or enzyme, affecting its function.
47. Why do only certain enantiomers bind effectively in the human body?
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Because biological receptors are shape-specific, and only one enantiomer fits properly.
48. Explain why structural isomers have different physical properties.
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Because the arrangement of atoms affects boiling point, melting point, and reactivity.
49. How does the carbon skeleton vary in organic molecules?
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It can differ in length, branching, double bond position, and ring formation.
50. Give an example of a naturally occurring molecule that includes a hydrocarbon chain.
Show Answer
Fats, which have long hydrocarbon tails used for energy storage.