chemistry : class12 Halogen identity effect : Physical properties of haloalkanes : Haloalkanes and Haloarenes MCQ Questions and Answers
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Halogen identity effect
MCQ questions and answers.
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MCQ Questions
1. Among chloromethane, bromomethane, and iodomethane, which compound generally has the highest boiling point?
A.
Chloromethane
B.
Bromomethane
C.
Iodomethane
D.
All three have the same boiling point
Correct Answer:
Iodomethane
Explanation:
For methyl halides, boiling point generally increases from chloro to bromo to iodo derivative because the molar mass and polarizability increase.
2. Which haloalkane generally has the greatest molar mass among the following compounds?
A.
Fluoroethane
B.
Chloroethane
C.
Bromoethane
D.
Iodoethane
Correct Answer:
Iodoethane
Explanation:
Iodine is the heaviest halogen listed, so replacing hydrogen with iodine gives the highest molar mass in this series.
3. For haloalkanes having the same alkyl group, replacing chlorine by bromine generally causes the boiling point to:
A.
Decrease
B.
Increase
C.
Remain exactly unchanged
D.
Become zero
Correct Answer:
Increase
Explanation:
Bromine has greater atomic mass and polarizability than chlorine, which generally strengthens dispersion forces and raises the boiling point.
4. Which compound generally has the lowest boiling point among the following methyl halides?
A.
Methyl fluoride
B.
Methyl chloride
C.
Methyl bromide
D.
Methyl iodide
Correct Answer:
Methyl fluoride
Explanation:
Methyl fluoride has the lowest molar mass and comparatively low polarizability among these methyl halides, so it generally has the lowest boiling point.
5. For haloalkanes with the same carbon chain, density generally increases when the halogen changes from:
A.
Iodine to fluorine
B.
Bromine to chlorine
C.
Fluorine to iodine
D.
Iodine to bromine
Correct Answer:
Fluorine to iodine
Explanation:
The heavier halogen increases the molar mass of the haloalkane, and density generally increases as the halogen changes from fluorine to iodine.
6. Which factor is mainly responsible for the increase in boiling point from chloroethane to bromoethane?
A.
Decrease in molecular mass
B.
Increase in polarizability
C.
Formation of hydrogen bonds
D.
Decrease in the number of electrons
Correct Answer:
Increase in polarizability
Explanation:
Bromine has a larger, more easily polarizable electron cloud than chlorine, increasing dispersion forces and generally raising the boiling point.
7. Among the following compounds, which one generally has the greatest density?
A.
Fluoropropane
B.
Chloropropane
C.
Bromopropane
D.
Iodopropane
Correct Answer:
Iodopropane
Explanation:
With the same propyl group, iodine contributes the greatest mass, so iodopropane generally has the greatest density in the series.
8. What is the usual boiling-point order for methyl halides?
A.
CH3I < CH3Br < CH3Cl < CH3F
B.
CH3F < CH3Cl < CH3Br < CH3I
C.
CH3Cl < CH3F < CH3I < CH3Br
D.
CH3Br < CH3I < CH3F < CH3Cl
Correct Answer:
CH3F < CH3Cl < CH3Br < CH3I
Explanation:
For methyl halides, boiling point generally increases with increasing halogen size, molar mass, and polarizability from fluorine to iodine.
9. Which haloalkane is expected to be more easily polarizable?
A.
Fluoroethane
B.
Chloroethane
C.
Bromoethane
D.
Iodoethane
Correct Answer:
Iodoethane
Explanation:
Iodine has the largest electron cloud among the halogens listed, making iodoethane the most easily polarizable.
10. When the halogen in a haloalkane is changed from chlorine to iodine while the carbon skeleton remains the same, the molecular mass generally:
A.
Decreases greatly
B.
Increases
C.
Remains unchanged
D.
Becomes equal to the carbon mass
Correct Answer:
Increases
Explanation:
Iodine has a much greater atomic mass than chlorine, so replacing chlorine with iodine increases the molecular mass of the haloalkane.
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