1.2 Bonding
Section A
For each of the questions only one of the lettered responses (A - D) is correct.
Select the correct
response in each case and mark its code letter by connecting the dots as
illustrated on the answer sheet.
1. In which one of the following
pairs do both compounds contain multiple bonds between atoms?
A BeCl2 and BCl3
B CCl4 and HCl
C SF6 and H2S
D C2H4
and CO2
2. In which one of the following substances is
the carbon-carbon bond the shortest?
A ethane
B ethene
C benzene
D polythene
3. Which
one of the following substances is most polar?
A carbon dioxide
B chloromethane
C hydrogen fluoride
D fluorine
4. Elements
P and Q combine by ionic bonding. P and Q most likely belong to the following
groups in the Periodic Table.
P Q
A I I
B I II
C I VII
D VI VII
5. In which one of the following salts would you expect the bond to
have the greatest ionic character?
A LiCl
B LiF
C KCl
D KF
6. Which molecule
does not contain non-bonding electron
pairs?
A BF3
B Cl2
C CH4
D HBr
7. Which one of the following atoms does not obey the octet rule in the compound given?
A carbon in CO2
B fluorine in BF3
C nitrogen in NH3
D sulphur in SF6
8. Which one of the following diagrams
represents a species containing a co-ordinate bond?
9. In which one of the following series are the elements in order of
increasing electronegativity?
A F Cl Br I
B Na Mg Al Si
C O S Se Te
D Be Mg Ca Sr
Section B
Answer all questions in the spaces provided
1.
(a) What is meant by the term
electronegativity?
[2]
(b)
Explain,
using the concept of electronegativity, whether you would expect carbon disulphide and hydrogen sulphide to be polar
molecules.
[4]
2.
An outline of the Periodic Table is shown
below.
(a)
Indicate on it the position of the
s-block, p-block and d-block elements.
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[2]
(b)
Write the electronic configuration for
(i) a potassium atom
[1]
(ii)
a sulphur atom
[1]
(c) Write the empirical formula for potassium
sulphide indicating the charges on the ions.
[1]
3.
Beryllium occurs to a small extent in the earth's crust. It is a steel-grey metal, which is extremely
light. Beryllium dissolves in hydrochloric acid to form beryllium chloride.
(i) Write an equation for the reaction.
[1]
(ii) Use
a dot and cross diagram to show the electronic structure of beryllium chloride.
[2]
(ii)
State the octet rule
and explain why it does not apply to beryllium chloride.
[2]
4. Sulphur
hexafluoride was discovered by Moissan in 1900 by burning sulphur in fluorine. It melts at -5 1 oC and is a gas
at room temperature.
(a) (i) Sulphur
exists as S8 molecules.
Write an equation for the reaction
of sulphur with fluorine.
[2]
(ii) Calculate the mass of sulphur hexafluoride, measured at
20 oC and a pressure of one atmosphere, which may be obtained by
burning 64 mg of sulphur in 144 cm3 of fluorine gas.
[3]
(b) The
shape of a molecule of sulphur hexafluoride can be explained by electron pair
repulsion theory.
Draw a
dot and cross diagram for sulphur hexafluoride.
[2]
(ii) Comment
on the octet rule as applied to sulphur hexafluoride.
[2]
(iii) Draw
the three-dimensional structure and name the shape of a sulphur hexafluoride
molecule.
name [2]
(iv) Explain the shape of this molecule.
[2]
(c) Sulphur
hexafluoride is remarkably resistant to reaction with other substances despite
the polarity of the bonds.
Theoretically, the enthalpy change for the hydrolysis of sulphur
hexafluoride is exothermic.
(i) Using
the following electronegativity values indicate and explain the polarity of the
sulphur-fluorine bond.
sulphur 2.5
fluorine 4.0
[2]
(ii) Use
the following bond enthalpies to calculate the enthalpy change for the
following reaction:
SF6
+ 3H2O SO3 + 6HF
bond bond
enthalphy/ kJ mol-1
S-F 326
O-H 464
S-O
(in SO3) 469
H-F 568
enthalpy
change = kJ mol-1 [3]
5. The
American chemist, Linus Pauling, conceived the idea of electronegativity.
The electronegatives of some elements are given below:
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H 2.1 |
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He - |
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Li 1.0 |
Be 1.5 |
B 2.0 |
C 2.5 |
N 3.0 |
0 3.5 |
F 4.0 |
Ne - |
|
Na 0.9 |
Mg 1.2 |
Al 1.5 |
Si 1.8 |
P 2.1 |
S 2.5 |
Cl 3.0 |
Ar - |
|
K 0.8 |
Ca 1.0 |
Ga 1.6 |
Ge 1.81 |
As 2.0 |
Se 2.4 |
Br 2.81 |
Kr - |
(a) (i) Explain
the term electronegativity.
[2]
(ii) Suggest
why no values are given for the elements in the right-hand column.
[1]
(iii) Suggest
why the electronegativity increases across the period from sodium to chlorine.
[2]
(b) (i) Using
the data in the table, underline those molecules below which contain one or
more polar bonds.
BrF PH 3 CCl4 SO2 [2]
(ii) Which
molecule contains the most polar bond?
[1]
6. All
along the coast, winter storms produce sea-spray, an invigorating mixture of
oxygen, nitrogen, carbon dioxide, water, particles of sea-weed, fine particles
of sodium chloride and other salts. Contrary
to popular belief, if there is ozone in sea spray, it is in quantities which
would be undetectable by us.
(a) Using
a dot and cross diagram, draw the structure of carbon dioxide.
[2]
(b) The
spray is produced as the sea dashes against coastal rocks. These are giant covalent silicate structures
which erode slowly over many years.
Water, on the other hand, is a molecular covalent substance. Explain the terms giant covalent and molecular
covalent.
[3]
(c)
Ozone,
O3, has the structure.
Referring
to this structure, suggest and explain the shape of an ozone molecule based on
electron pair repulsion theory.
[2]
(d) Electrolysis
of sea water produces chlorine and sodium hydroxide which can react together to
give further products under different conditions.
(i)
Write the equation
for the reaction of chlorine with hot concentrated sodium hydroxide solution.
[2]
(ii) State
the oxidation states of chlorine at the start and the end of this reaction.
Start
End and [3]