Chemistry 11 (HL)
Unit 4 / IB Topic 14.2
Covalent Bonding 5 Practice Problems
Hybridisation and Sigma & Pi Bonds
1.
Explain the meaning of “hybrid orbitals”.
2.
Complete this table for hybrid orbitals:
hybrid
orbital
sp
3
sp
2
description of how it forms
shape around
atoms with
these hybrid
orbitals
angle
between
hybrid
orbitals
sp
3.
What type of hybrid orbitals does the central atom have in these molecules/ions?
HINT: Draw the Lewis structure first, and look at the number of NCCs around each atom.
a) CF4
b)
BH3
e) CO2
f)
BH4
1-
c) CH2O
d) NH3
g) C2H2
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Chemistry 11 (HL)
4.
Unit 4 / IB Topic 14.2
Compare the formation of sigma bonds and pi bonds.
• similarities:
• differences:
5.
6.
How many sigma and pi bonds are in these molecules?
HINT: Draw the Lewis structures first.
a) CO2
b) NH3
c) H2CO
d)
e) C2H2
f) O3
C 2H 4
Draw a Lewis structure for ethanoic acid, CH3COOH.
Identify the types of hybrid orbitals for each of the carbon atoms and each of the oxygen
atoms.
How many sigma bonds are present in the molecule?
How many pi bonds are present in the molecule?
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Chemistry 11 (HL)
7.
Unit 4 / IB Topic 14.2
Urea, H2NCONH2, is present in animal urine.
Draw the Lewis structure for urea. (Hint: The oxygen is bonded to the carbon atom with a
double bond.)
What is the hybridization of the carbon and the nitrogen atoms?
What is the shape around the carbon atom and around the nitrogen atoms?
What are the bond angles around the carbon atom and around the nitrogen atom?
How many sigma bonds are present?
How many pi bonds are present?
8.
The structure of ascorbic acid (vitamin C) is shown below.
a)
Determine the number of sigma and
pi bonds in ascorbic acid.
b)
State the number of lone electron
pairs in this structure.
c)
State the hybridization of each
carbon and oxygen atom in the
molecule.
d)
Circle the carbon atoms having a
trigonal planar shape.
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Chemistry 11 (HL)
9.
Unit 4 / IB Topic 14.2
Caffeine has the formula C8H10N4O2. A model of caffeine is shown below. Atoms without
symbols are hydrogen atoms.
C
N
C
N*
N
O
C
C*
C
N
C
C
C
O
a)
Several atoms in this molecule have lone electron pairs. Add the missing lone
electron pairs on this molecule.
b)
Identify the hybridization, bond angle and shape around the atoms marked N*, C*
and O.
c)
Circle a carbon atom with sp hybridization.
3
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