Questions
Q1.
Nitrogen and oxygen are present in the air.
(a) In industry, nitrogen and oxygen are obtained from air.
(i) Give the name of the process used.
(1)
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(ii) State why the air is cooled before the start of the process.
(1)
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(b) Complete the sentence by putting a cross (
) in the box next to your answer.
Oxygen has a low boiling point because there are
(1)
A weak covalent bonds between the oxygen atoms
B weak covalent bonds between the oxygen molecules
C weak forces of attraction between the oxygen atoms
D weak forces of attraction between the oxygen molecules
(c) Another gas present in air is carbon dioxide, CO2.
There are covalent bonds between the atoms in a molecule of carbon dioxide.
(i) Describe what is meant by a covalent bond.
(2)
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(ii) The electronic configuration of oxygen (atomic number 8) is 2.6.
Give the electronic configuration of carbon (atomic number 6).
(1)
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(iii) Draw a dot and cross diagram of a molecule of carbon dioxide.
Show outer electrons only.
(2)
(Total for Question = 8 marks)
Q2.
The atomic number of carbon is 6 and of fluorine is 9.
Carbon and fluorine atoms are combined in a tetrafluoromethane molecule, CF4.
Draw a dot and cross diagram of a tetrafluoromethane molecule.
Show outer electrons only.
(2)
Q3.
(a) Complete the sentence by putting a cross (
) in the box next to your answer.
A mixture of two immiscible liquids can be separated by using
(1)
A fractional distillation
B a separating funnel
C evaporation
D filtration
(b) Oxygen is a simple molecular, covalent substance.
(i) The electronic configuration of oxygen is 2.6.
Draw a dot and cross diagram for a molecule of oxygen, O2.
Show the outer electrons only.
(3)
(ii) The boiling point of oxygen is –183 °C.
Explain, in terms of the forces between the molecules, why oxygen has a very low boiling point.
(2)
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(c) Describe how oxygen and nitrogen are obtained from liquid air by fractional distillation.
(3)
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(Total for Question is 9 marks)
Q4.
Structures
The table shows some properties of diamond and graphite.
diamond
graphite
colourless crystals
black, shiny solid
very hard
flakes easily
does not conduct electricity
conducts electricity
(a) (i) Suggest why diamond and graphite might be expected to have similar properties.
(1)
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(ii) By referring to its structure, explain why diamond is very hard.
(3)
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(iii) By referring to its structure, explain why graphite flakes easily.
(2)
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(b) Complete the sentence by putting a cross ( ) in the box next to your answer.
Carbon dioxide is a gas at room temperature.
A carbon dioxide molecule is a
(1)
A giant molecule that has covalent bonds
B giant molecule that has ionic bonds
C simple molecule that has covalent bonds
D simple molecule that has ionic bonds
(c) The atomic number of carbon is 6 and of fluorine is 9.
Carbon and fluorine atoms are combined in a tetrafluoromethane molecule, CF4.
Draw a dot and cross diagram of a tetrafluoromethane molecule.
Show outer electrons only.
(2)
Mark Scheme
Q1.
Answer
(a)(i)
(a)(ii)
(b)
fractional distillation
to make it liquid
D weak forces of
Acceptable
answers
Mark
(1)
liquefy/condense
to remove water
(vapour)
to remove carbon
dioxide
(1)
(1)
(c)(i)
(c)(ii)
(c)(iii)
attraction between
the oxygen
molecules
An description
including
 shared
(electrons) (1)
 pair(s) of
electrons (between
atoms) (1)
2.4
diagram showing
 any shared pair
of electrons between
a carbon and oxygen
atom in CO2
molecule (1)
 rest of molecule
correct (1)
Ignore reference to
complete/full shells
Ignore reference to
between two metals
Ignore reference to
between metal and
non-metal
Ignore reference to
between molecules
Any reference to
between ions scores
0
(2)
(1)
Must have O C O
arrangement If any
atom labelled must
be correct Ignore
inner electrons even
if wrong electrons
can be on/in ring or
no ring
Ignore intersecting
circles Accept all
permutations of dots
and crosses
(2)
Acceptable answers
Mark
Q2.
Question
Number
Answer
• four bonding pairs
shown (1) • six non
bonded electrons on
each fluorine atom
(1)
Answer
(a)(i)
(b)(i)
(b)(ii)
(2)
Acceptable
answers
B
 electrons shared
/ between atoms (1)
 2 pairs of/four
electrons shared /
between two atoms
(1)
 4 additional
electrons on both
oxygen atoms (1)
An explanation
linking the following
second marking
ignore any inner
electrons shown
3rd Mark is
dependent on 2nd
intermolecular
forces/bonds
between molecules
Mark
(1)
(3)
(2)
(c)
point is dependent
on the first
 forces (between
the molecules) are
weak (1)
 therefore little
heat/energy needed
to separate
molecules/break
these forces (1)
A description
including three from
 (liquid air enters)
(fractionating)
column (1)
 (liquid air)
warms/heats/boils
(1)
 (gaseous)
nitrogen/lower
boiling point from top
of column (1)
 (liquid)
oxygen/higher
boiling point from
bottom of column (1)
reject intramolecular
force/covalent
bond/ionic bond
(3)
ignore references to
cooling air etc.
can be separated
because they have
different boiling
points (1) alternative
to last two marking
points
(Total for question =9 marks)
Question
Number
(a)(i)
Acceptable answers
both (pure forms of)
carbon / both giant
molecular
Question
Number
(a)(ii)
Answer
Answer
An explanation
linking the following
• (in) layers (1)
• weak forces
between layers (1)
Mark
(1)
Acceptable answers
An explanation
linking three of the
following points
• (every) carbon
atom forms four
bonds (1) • strong
bonds / hard to
separate atoms from
lattice (1) • covalent
bonds (1) • covalent
bonds (1)
Question
Number
(a)(iii)
Answer
Mark
(3)
Acceptable answers
Mark
(2)
Question
Number
(b)
Acceptable answers
Mark
(1)
C
Question
Number
(c)
Answer
Answer
• four bonding pairs
shown (1) • six non
bonded electrons on
each fluorine atom
(1)
Acceptable answers
Mark
(2)
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Covalent bonding past paper questions