Question 8 [Chemical Bonding >3.2 Covalent bonding and
co-ordinate (dative covalent) bonding including shapes of simple molecules]
Solid carbon dioxide, CO2, is similar to solid
iodine, I2, in its structure and properties. Carbon is
in Group 14. Silica, SiO2, is a Group 14 compound.
Which statement about
solid CO2 and solid SiO2 is correct?
A Both solids exist in a lattice structure.
B Both solids have a simple molecular structure.
C Both solids have atoms joined by single covalent
bonds.
D Both solids change spontaneously to gas at s.t.p.
Reference: Past
Exam Paper – Chemistry (9701) March 2016 Paper 12 Q8
Solution:
Answer: A
Option A: “It should be known
that solid I2 has a simple molecular lattice, therefore it can be
deduced from the information in the question that solid CO2 does
too”
Option B can be discredited since we know that SiO2 has a
similar structure to diamond, i.e, a giant covalent structure, not simple
molecular.
Option C can be eliminated. While SiO2 has four single bonds,
CO2 has two double bonds and is linear rather than tetrahedral like
SiO2.
Option D can be eliminated since at stp, SiO2 is a solid and
will not change spontaneously (naturally) into a gas.
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