Aristo Chemistry Book 3 Answer

11273 Words Nov 25th, 2014 46 Pages
HKDSE CHEMISTRY – A Modern View (Chemistry)
Coursebook 3
Suggested answers
Chapter 25 Simple molecular substances with non-octet structures and shapes of simple molecules
Page Number
Class Practice
1
Chapter Exercise
2
Chapter 26 Bond polarity
Class Practice
4
Chapter Exercise
5
Chapter 27 Intermolecular forces
Class Practice
7
Chapter Exercise
9
Chapter 28 Structures and properties of molecular crystals
Class Practice
11
Chapter Exercise
12
Part Exercise
14
Chapter 29 Chemical cells in daily life
Class Practice
17
Chapter Exercise
18
Chapter 30 Simple chemical cells
Class Practice
21
Chapter Exercise
22
Chapter 31 Redox reactions
Class Practice
24
Chapter Exercise
26
Chapter 32 Redox reactions in chemical cells
Class Practice
29
Chapter
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(b)

A27.2
1. (a) Non-polar molecules (b) Dispersion forces (c) (i) The statement is correct as butane has a higher boiling point than that of propane. The strength of dispersion forces increases with increasing molecular size as there is a greater chance of uneven distribution of electrons in a larger molecule. (ii) The statement is incorrect as butane has a higher boiling point than that of 2-methylpropane. Butane (straight-chain hydrocarbon) has a long, thin shape. This contributes to a larger contact surface area between butane molecules, resulting in larger dispersion forces.
2. ClF and CH2Cl2 are polar in nature and their molecules are attracted by both dipole-dipole forces and dispersion forces. On the other hand, F2 and Cl2 are non-polar in nature and their molecules are attracted by dispersion forces only. As a result, ClF and CH2Cl2 have higher boiling points than those of F2 and Cl2. Since the molecular size of CH2Cl2 is larger than that of ClF, the dispersion forces between CH2Cl2 molecules are larger. So CH2Cl2 has a higher boiling point. Similarly, since the molecular size of Cl2 is larger than that of F2, Cl2 has a higher boiling point.
3. (a) CH3F is polar in nature and its molecules are attracted by both
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