chemistry : class11 Molecular Solids : Melting point : States of Matter: Gases and Liquids MCQ Questions and Answers
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Molecular Solids
MCQ questions and answers.
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MCQ Questions
1. Molecular solids are made up of which particles?
A.
Positive and negative ions
B.
Neutral molecules
C.
Metal atoms only
D.
Free electrons
Correct Answer:
Neutral molecules
Explanation:
Molecular solids consist of neutral molecules held together by intermolecular forces.
2. Why do most molecular solids have relatively low melting points?
A.
They contain strong metallic bonds
B.
Their molecules are held by relatively weak intermolecular forces
C.
They contain freely moving ions
D.
Their atoms are arranged randomly
Correct Answer:
Their molecules are held by relatively weak intermolecular forces
Explanation:
The intermolecular forces between molecules in most molecular solids are weaker than ionic or covalent network bonds, so less energy is needed to melt them.
3. Which of the following is a molecular solid?
A.
Sodium chloride
B.
Copper
C.
Solid iodine
D.
Diamond
Correct Answer:
Solid iodine
Explanation:
Solid iodine consists of iodine molecules held together by intermolecular forces, making it a molecular solid.
4. What happens to the molecules of a molecular solid when it is heated to its melting point?
A.
The molecules are converted into ions
B.
The intermolecular attractions are overcome sufficiently for the molecules to move more freely
C.
The molecules lose all their atoms
D.
The molecules become metal atoms
Correct Answer:
The intermolecular attractions are overcome sufficiently for the molecules to move more freely
Explanation:
At the melting point, heating provides enough energy to weaken the attractions between molecules, allowing them to move in the liquid state.
5. Which intermolecular force commonly holds nonpolar molecular solids together?
A.
London dispersion force
B.
Ionic bond
C.
Metallic bond
D.
Covalent network bond
Correct Answer:
London dispersion force
Explanation:
Nonpolar molecules in molecular solids are commonly held together by London dispersion forces.
6. Which molecular solid generally has a higher melting point because of hydrogen bonding?
A.
Ice
B.
Solid neon
C.
Solid argon
D.
Solid methane
Correct Answer:
Ice
Explanation:
Ice is a molecular solid in which water molecules are linked by hydrogen bonds, giving it a higher melting point than many molecular solids with weaker attractions.
7. Compared with a molecular solid having weak intermolecular forces, a molecular solid having stronger intermolecular forces usually has a:
A.
Lower melting point
B.
Higher melting point
C.
Zero melting point
D.
Melting point unrelated to intermolecular forces
Correct Answer:
Higher melting point
Explanation:
Stronger intermolecular forces require more energy to overcome, so the molecular solid melts at a higher temperature.
8. Which substance is an example of a molecular solid with molecules held mainly by dispersion forces?
A.
Solid carbon dioxide
B.
Sodium chloride
C.
Magnesium oxide
D.
Copper
Correct Answer:
Solid carbon dioxide
Explanation:
Solid carbon dioxide consists of nonpolar CO2 molecules held mainly by London dispersion forces.
9. Molecular solids are generally poor conductors of electricity in the solid state because they:
A.
Have no freely moving charged particles
B.
Contain many free ions
C.
Have a sea of mobile electrons
D.
Are always made of metals
Correct Answer:
Have no freely moving charged particles
Explanation:
Molecular solids contain neutral molecules and generally lack mobile ions or electrons, so they do not conduct electricity well.
10. Which property is most characteristic of many molecular solids?
A.
Very high melting point due to a giant covalent network
B.
Relatively low melting point due to weak forces between molecules
C.
Excellent electrical conductivity as solids
D.
Formation of positive and negative ions in the crystal
Correct Answer:
Relatively low melting point due to weak forces between molecules
Explanation:
Many molecular solids melt relatively easily because their molecules are held together by weak intermolecular attractions.
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