chemistry : class12 Carbon chain length effect : Physical properties of haloalkanes : Haloalkanes and Haloarenes MCQ Questions and Answers
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Carbon chain length effect
MCQ questions and answers.
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MCQ Questions
1. What generally happens to the boiling point of haloalkanes when the carbon chain length increases?
A.
It generally increases
B.
It always becomes zero
C.
It generally decreases
D.
It remains exactly unchanged
Correct Answer:
It generally increases
Explanation:
As the carbon chain becomes longer, the molecular size and surface area increase, strengthening London dispersion forces and generally raising the boiling point.
2. Which haloalkane is expected to have the highest boiling point among the following compounds with the same halogen?
A.
Chloromethane
B.
Chloroethane
C.
1-chloropropane
D.
1-chlorobutane
Correct Answer:
1-chlorobutane
Explanation:
For haloalkanes containing the same halogen, increasing the carbon chain length generally increases the boiling point. 1-Chlorobutane has the longest carbon chain here.
3. How does increasing carbon chain length generally affect the volatility of haloalkanes?
A.
Volatility generally increases
B.
Volatility generally decreases
C.
Volatility becomes independent of temperature
D.
Volatility changes into ionization
Correct Answer:
Volatility generally decreases
Explanation:
Longer-chain haloalkanes have stronger intermolecular dispersion forces, so they evaporate less readily and generally show lower volatility.
4. Which physical property generally increases as the carbon chain length of a homologous series of haloalkanes increases?
A.
Boiling point
B.
Ease of evaporation
C.
Vapour pressure at the same temperature
D.
Tendency to remain gaseous
Correct Answer:
Boiling point
Explanation:
A longer carbon chain provides a larger molecular surface and stronger dispersion forces, causing the boiling point to generally increase.
5. Why do longer-chain haloalkanes generally have higher boiling points than shorter-chain haloalkanes of the same type?
A.
They have stronger London dispersion forces
B.
They contain fewer carbon atoms
C.
They have weaker molecular attractions
D.
They have no intermolecular forces
Correct Answer:
They have stronger London dispersion forces
Explanation:
Increasing carbon chain length increases molecular size and electron-cloud surface area, which strengthens London dispersion forces and raises the boiling point.
6. Which compound is expected to be the most volatile among the following straight-chain bromoalkanes?
A.
1-Bromopropane
B.
1-Bromobutane
C.
1-Bromopentane
D.
1-Bromohexane
Correct Answer:
1-Bromopropane
Explanation:
Among these compounds with the same halogen, 1-bromopropane has the shortest carbon chain. Shorter-chain haloalkanes generally have weaker dispersion forces and higher volatility.
7. In a homologous series of haloalkanes, what generally happens to intermolecular attraction as the carbon chain becomes longer?
A.
It generally becomes stronger
B.
It disappears completely
C.
It generally becomes weaker
D.
It changes into ionic attraction
Correct Answer:
It generally becomes stronger
Explanation:
A longer carbon chain increases the size and contact surface of the molecules, strengthening London dispersion forces between haloalkane molecules.
8. Which haloalkane would generally have the lowest boiling point among the following compounds containing chlorine?
A.
1-Chloropentane
B.
1-Chlorobutane
C.
1-Chloropropane
D.
Chloroethane
Correct Answer:
Chloroethane
Explanation:
Chloroethane has the shortest carbon chain in the list. Shorter-chain haloalkanes generally have weaker dispersion forces and lower boiling points.
9. As the carbon chain length increases in haloalkanes, what generally happens to their vapour pressure at the same temperature?
A.
It generally decreases
B.
It generally increases greatly
C.
It becomes exactly equal to atmospheric pressure
D.
It becomes unrelated to boiling point
Correct Answer:
It generally decreases
Explanation:
Longer-chain haloalkanes have stronger intermolecular attractions, so fewer molecules escape into the vapour phase at the same temperature, lowering vapour pressure.
10. Which statement correctly describes the effect of increasing carbon chain length on the physical state of haloalkanes at room temperature?
A.
They generally become less volatile and may change from gases or liquids to liquids or solids
B.
They always become gases
C.
They become completely nonpolar only because the chain is longer
D.
They always change directly into plasma
Correct Answer:
They generally become less volatile and may change from gases or liquids to liquids or solids
Explanation:
Increasing carbon chain length raises intermolecular dispersion forces and boiling points, so haloalkanes generally become less volatile and may have higher physical states at room temperature.
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