DSE Chemistry
DSE Chemistry: Microscopic World II — Practice Questions & Answers
Electronegativity and bond polarity, the three types of intermolecular force, and how giant and simple structures explain physical properties.
354 practice questions available for this topic — here are 10 with full answers and explanations.
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Practice questions with answers
1
Multiple choice · Medium
Which of the following molecules is polar?
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WhyNH3 has an unsymmetrical shape, so its bond dipoles do not cancel and the molecule is polar.
2
Multiple choice · Medium
A covalent bond between two different atoms is polar when the atoms have different
- electronegativities
- numbers of neutrons
- physical states
- relative atomic masses only
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WhyA difference in electronegativity makes the shared electrons unevenly distributed.
3
Multiple choice · Hard
Carbon tetrachloride (CCl4) contains polar C-Cl bonds but is a non-polar molecule because
- its symmetrical shape causes the bond dipoles to cancel
- the C-Cl bonds are non-polar
- chlorine is less electronegative than carbon
- it contains ionic bonds
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WhyIts symmetrical shape makes the four bond dipoles cancel one another.
4
Fill in the blank · Medium
A bond is polar when the two atoms joined have different values of .
Answer:
electronegativity
WhyThe more electronegative atom carries a partial negative charge.
5
Fill in the blank · Medium
A molecule containing polar bonds is non-polar overall when the bond dipoles because of a symmetrical shape.
Answer:
cancel / cancel out
WhyExamples are CO2 and CCl4.
6
Fill in the blank · Easy
Ammonia is a molecule, so it dissolves readily in water.
Answer:
polar
WhyIts unsymmetrical shape gives it a net dipole.
7
Multiple choice · Medium
Silicon is an element in Group IV and its oxide is SiO2. Which statement about silicon and its oxide is correct?
- SiO2 is a hard material at room temperature
- Silicon is a good conductor of heat
- Silicon exists as simple molecules
- SiO2 dissolves in water to give an acidic solution
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WhySiO2 is a giant covalent solid and is hard at room temperature.
8
Multiple choice · Easy
Which substance has a giant covalent structure?
- diamond
- iodine
- sodium chloride
- dry ice
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WhyDiamond has a giant covalent network.
9
Multiple choice · Hard
Both diamond and graphite are giant covalent. Which statement correctly compares them?
- Graphite conducts electricity but diamond does not
- Diamond is soft but graphite is hard
- Both are made of small molecules
- Both have low melting points
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WhyGraphite conducts because of delocalised electrons; diamond does not.
10
Fill in the blank · Medium
In silicon dioxide, each silicon atom is bonded to four oxygen atoms and each oxygen atom is bonded to silicon atoms.
Answer:
2 / two
WhyEach O bridges two Si atoms.
Key terms in Microscopic World II
Electronegativity: A measure of the tendency of an atom in a bond to attract the shared electron pair.
Polar covalent bond: A covalent bond in which electrons are shared unequally, giving partial charges.
Bond polarity: The uneven distribution of electron density caused by a difference in electronegativity.
Polar molecule: A molecule with a net dipole due to an asymmetric arrangement of polar bonds.
Non-polar molecule: A molecule with no overall dipole because bond dipoles cancel or bonds are non-polar.
Van der Waals forces: Weak attractive forces between molecules arising from temporary and induced dipoles.
Intermolecular force: An attractive force acting between separate molecules.
Hydrogen bond: A strong dipole attraction between H bonded to N, O or F and a lone pair on another such atom.
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