Unit 3 Topic 14
Review
1. When the compounds C2H6, C2H4, C2H2 and C6H6 are arranged in order of increasing C-C bond lengths (shortest
first) the correct order is:
a. C2H6
b. C6H6
c. C2H2
d. C2H2
C2H4
C2H4
C6H6
C2H4
C2H2
C2H2
C2H2
C6H6
C6H6
C2H6
C2H6
C2H6
2. The number of π bonds and hybridization of the C in a molecule of hydrogen cyanide, HCN are:
Number of π bonds
hybridization
a.
3
sp2
b.
2
sp
c.
1
sp2
d.
2
sp3
3. Which of the following contains delocalized electrons?
a. CO2
b. O3
c. SiO2
d. OCl2
4. In which of the following is the distribution of electron pairs around the central atom octahedral?
a. BCl4-
b. SF4
c. PCl4+
d. XeF4
5. a. Explain the term ‘hybridization’.
b. Predict the hybridization of the carbon atoms in ethene (C2H4) and ethyne (C2H2)
c. Explain, by reference to ethene and ethyne, what is meant by the terms ‘sigma bond’ and ‘pi bond’.
Unit 3 Topic 14
Review
6. a. Use the valence shell electron pair repulsion theory to predict the shapes and bond angles of the following
molecules or ions:
i. SO42- ii. XeF4 iii. SF4
b. Explain whether XeF4 is polar or non-polar.
c. Explain how you would expect the S-O bond length in SO42- to compare with that in SO2.
7. Draw Lewis structures for each of the following molecules that do not obey the octet rule for the central atom,
and describe their molecular geometry
CIF3
PF5
SF4
CIF5
SbF6-
BF3
Unit 3 Topic 14
Review
8. Complete the following table for the atoms indicated in bold type. You should sketch the molecule.
Molecule
Hybridization
CH3CH2
sp3
CH2CH2
Shape
Angle
trigonal planar
O2
not relevant – 2 atoms
CH3CHO
12Ø˚
CH3COCH3
CH3CN
N2
not relevant – 2 atoms
CH2NH2
1Ø7˚ (one lone pair)
9. Identify the hybridization and bond angles in each of the indicated atoms.
Unit 3 Topic 14
Review
10. For each of the following, draw all possible resonance structures and determine their bond orders.
SCN-
SO2
SO3
CO32-