Name: ………………………………………………………………..
Date Due: ………………………………………………………………..
Year 12 80% A
70% B
AS Level Chemistry 60% C
2007 - 2008 50% D
40% E
Below U
1.3
Assessed Homework %
Bonding
55
10.3 Bonding Assessed Homework
1. (a) An ammonium ion, made by the reaction between ammonia molecule and a
hydrogen ion, can be represented as shown in the diagram below.
+
H
N H
H
H
(i) Name the type of bond represented in the diagram N-H
……………………………………………………………………………………………….
(ii) Name the type of bond represented in the diagram by N→H
……………………………………………………………………………
(iii) In terms of electrons, explain why an arrow is used to represent this N H
bond
…………………………………………………………………………………………………
…………………………………………………………………………………………………
(iv) In terms of electron pairs, explain why the bond angles in the NH 4+ ion are all
109o28’
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
(7)
(b) Define the term electronegativity
…………………………………………………………………………………………………
…………………………………………………………………………………………………
(2)
δ δ
(c) A bond between nitrogen and hydrogen can be represented as N - H
+
(i) In this representation, what is the meaning of the symbol δ ?
…………………………………………………………………………………………………
1
10.3 Bonding Assessed Homework
(ii) From this bond representation, what can be deduced about the electronegativity of
hydrogen relative to that of nitrogen?
……………………………………………………………………………………………………
……………………………………………………………………………………………………
(2)
(Total 11 marks)
2. (a) Both HF and HCl are molecules having a polar covalent bond. Their boiling points
are 293 K and 188 K respectively.
(i) State which property of the atoms involved causes a bond to be polar.
...........................................................................................................................
...........................................................................................................................
(ii) Explain, in terms of the intermolecular forces present in each compound,
why HF has a higher boiling point than HCl.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(4)
(b) When aluminium chloride reacts with chloride ions, as shown by the equation
below, a co-ordinate bond is formed.
– –
AlCl3 + Cl AlCl4
Explain how this co-ordinate bond is formed.
..................................................................................................................................
.................................................................................................................................
.................................................................................................................................
(2)
2
10.3 Bonding Assessed Homework
+
(c) Draw the shape of the PCl5 molecule and of the PCl4 ion. State the value(s) of
the bond angles.
+
PCl5 PCl4
Bond angle(s) ...................................... Bond angle(s)
..........................................
(4)
(Total 10 marks)
–
3. Lithium hydride, LiH, is an ionic compound containing the hydride ion, H
The reaction between LiH and aluminium chloride, AlCl3, produces the ionic compound
LiAlH4
(a) Balance the equation below which represents the reaction between LiH and AlCl3
LiH + AlCl3 LiAlH4 + LiCl
(1)
–
(b) Give the electronic configuration of the hydride ion, H
.....................………………………………………………………………………….
(1)
(c) Predict the shape of the AlH 4– ion. Explain why it has this shape.
Shape ..........................................................................................................………
Explanation .................................................................................................………
.....................………………………………………………………………………….
.....................………………………………………………………………………….
(3)
(d) A bond can be represented by H Al
Name this type of bond and explain how it is formed.
Type of bond ................................................................................................………
Explanation …………….…………………………………………………………….
3
10.3 Bonding Assessed Homework
.....................………………………………………………………………………….
(3)
(Total 8 marks)
4. The table below shows some values of melting points and some heat energies needed for
melting.
Substance I2 NaCl HF HCl HI
Melting point/K 387 1074 190 158 222
Heat energy for melting /kJ mol–1 7.9 28.9 3.9 2.0 2.9
(a) Name three types of intermolecular forces
Force 1 …………………………………………………………………………..
Force 2 …………………………………………………………………………..
Force 3 …………………………………………………………………………..
(3)
(b) (i) Describe the bonding in a crystal of iodine
………………………………………………………………………………………
……………………………………………………………………………………..
(ii) Name the crystal type which describes an iodine crystal
…………………………………………………………………………….
(iii) Explain why heat energy is required to melt an iodine crystal.
………………………………………………………………………………………
………………………………………………………………………………………
(4)
(c) In terms of intermolecular forces involved, suggest why
(i) hydrogen fluoride requires more heat energy for melting than does of
hydrogen chloride
………………………………………………………………………………………
………………………………………………………………………………………
4
10.3 Bonding Assessed Homework
………………………………………………………………………………………
……………………………………………………………………………………..
(ii) Hydrogen iodide requires more heat energy for melting than does hydrogen
chloride.
………………………………………………………………………………………
………………………………………………………………………………………
……………………………………………………………………………………..
(5)
(d) (i) Explain why the heat energy required to melt sodium chloride is large
………………………………………………………………………………………
………………………………………………………………………………………
(ii) The heat energy need to vaporise one mole of sodium chloride (171 KJ mol-
1
) is much greater than the heat energy required to melt one mole of sodium
chloride. Explain why this is so.
………………………………………………………………………………………
………………………………………………………………………………….….
(3)
(e) In terms of structure and bonding, suggest why graphite has a very high melting and
boiling point
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
(2)
(Total 17 marks)
5
10.3 Bonding Assessed Homework
5. The diagram below represents a section of a crystal of silicon dioxide.
Si
O O
O
Si Si
O
Si
O O
(a) Name an element which has a structure similar to this.
……………………………………………………………………………………. (1)
(b) Name the type of bonding between silicon and oxygen in this crystal
…………………………………………………………………………………….
(1)
(c) Name the type of structure illustrated by this diagram
…………………………………………………………………………………….
(1)
(d) Describe the motion of the atoms in this crystalline solid
…………………………………………………………………………………………………
……………………………………………………………………………………………….
(2)
(e) In terms of structure and bonding, describe what happens to the atoms in this
crystal when it melts
…………………………………………………………………………………………………
………………………………………………………………………………………………..
(f) Explain why this crystal is a non conductor of electricity in the solid state and why
graphite is a good conductor.
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
6
10.3 Bonding Assessed Homework
(4)
(Total 9 marks)
