1. science
2. phyiscs
3. atomic physics

C2 Mock Exam October 2014
C2.1 - C2.3
68 minutes
68 marks
Difficulty 3x1 4x2 2x3
Page 1 of 30
Q1.
The diagrams show five different atoms, A, B, C, D and E.
(a)
Which atom, A, B, C, D or E:
(i)
has an atomic number (proton number) of 3
Atom
(1)
(ii)
has a mass number of 2
Atom
(1)
(iii)
is in Group 2 of the periodic table?
Atom
(1)
(b)
Which two atoms from A, B, C, D and E are isotopes of the same element?
Atom
and
Atom
(1)
(c)
Which particle in an atom has a negative charge? .......................................
(1)
(Total 5 marks)
Page 2 of 30
Q2.
This question is about lithium and sodium.
(a)
Use the Chemistry Data Sheet to help you to answer this question.
In which group of the periodic table are lithium and sodium?
Group
(1)
(b)
A lithium atom can be represented as
The diagram represents the lithium atom.
(i)
Some particles in the nucleus have a positive charge.
What is the name of these particles? ......................................................................
(1)
(ii)
Some particles in the nucleus have no charge.
What is the name of these particles? ........................................................................
(1)
(iii)
Use the correct answer from the box to complete the sentence.
3
4
7
The mass number of this atom of lithium is
(1)
Page 3 of 30
(c)
Sodium reacts with chlorine to produce sodium chloride.
sodium
+
chlorine
sodium chloride
The diagram shows how the reaction happens.
Only the outer electrons are shown.
Draw a ring around the correct answer to complete each sentence.
gaining
(i)
A sodium atom changes into a sodium ion by
losing
an electron.
sharing
(1)
a negative
(ii)
A sodium ion has
no
charge.
a positive
(1)
covalent
(iii) The ions in sodium chloride are held together by strong
electrostatic forces.
magnetic
(1)
(d)
Sodium chloride is an ionic compound.
Tick ( ) two properties of ionic compounds.
Property
Tick ( )
Do not dissolve in water
High melting points
Low boiling points
Strong bonds
(2)
Page 4 of 30
(e)
(i)
The formula of sodium chloride is NaCl
Calculate the relative formula mass of sodium chloride.
Relative atomic masses: Na = 23; Cl = 35.5
.................................................................................................................
.................................................................................................................
Relative formula mass = .............................................
(1)
(ii)
Draw a ring around the correct answer to complete each sentence.
ion
The relative formula mass of a substance, in grams, is
one
isotope
of the substance.
mole
(1)
(f)
Nanoparticles of sodium chloride (salt) are used to flavour crisps.
What are nanoparticles?
........................................................................................................................
........................................................................................................................
(1)
(Total 12 marks)
Q3.
(a)
The symbol equation for the decomposition of hydrogen peroxide is:
2H2O2 → 2H 2O + O2
Complete the word equation for the decomposition of hydrogen peroxide.
Hydrogen peroxide → .................................... + ....................................
(1)
Page 5 of 30
(b)
A student did an experiment to see how quickly hydrogen peroxide decomposes.
The student used the apparatus shown below to measure the volume of oxygen.
(i)
Draw a straight line of best fit to complete the graph.
(1)
(ii)
Draw a circle around the anomalous point on the graph.
(1)
(iii)
What is the volume of oxygen given off after 15 seconds?
......................... cm3
(1)
(iv)
How did the volume of oxygen change between 0 and 25 seconds?
...............................................................................................................
(1)
Page 6 of 30
(c)
The student wanted to make the reaction faster.
Draw a ring around the correct answer to complete each sentence.
higher.
(i) To make the reaction faster, the temperature should be
lower.
the same.
(1)
more dilute.
(ii) To make the reaction faster, the hydrogen peroxide should be
more concentrated.
the same.
(1)
(d)
The diagram represents the bonding in oxygen.
O=O
Draw a ring around the correct answer to complete each sentence.
share
(i) When two oxygen atoms bond, the atoms
transfer
electrons.
delocalise
(1)
ionic
(ii) The oxygen atoms are joined by
metallic
bonds.
covalent
(1)
simple molecules.
(iii) Oxygen is made of
a giant lattice.
macromolecules.
(1)
(e)
When hydrogen peroxide decomposes water is produced.
Which two statements in the table explain why water is a liquid at room temperature?
Page 7 of 30
Tick ( ) the two statements.
Statement
Tick ( )
Water has a boiling point of 100 °C.
Water is made of ions.
Water has a melting point lower than room
temperature.
Water has a giant covalent structure.
(2)
(Total 12 marks)
Q4.
(a)
A tin of red kidney beans contains calcium chloride as a firming agent.
Calcium chloride is an ionic compound which contains calcium ions (Ca2+) and chloride
ions (Cl–).
(i)
The diagram on the left represents the electronic structure of a chlorine atom.
Complete a similar diagram on the right to represent a chloride ion.
(2)
Page 8 of 30
(ii)
Explain how a calcium atom changes into a calcium ion which has a 2+ charge.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(b)
Cola drinks contain phosphoric acid, H3PO4. The two equations show how phosphoric acid
can be made from phosphorus.
Balance these two equations.
(i)
P4 + ........ O2 → P4O10
(1)
(ii)
P4O10 + ................ H2O → 4H3PO4
(1)
(Total 6 marks)
Page 9 of 30
Q5.
Calamine lotion is used to treat itching. The main ingredients are two metal oxides.
(a)
One of the metal oxides has a relative formula mass (M r) of 81.
The formula of this metal oxide is MO.
(M is not the correct symbol for the metal.)
The relative atomic mass (Ar) of oxygen is 16.
(i)
Calculate the relative atomic mass (Ar) of metal M.
...............................................................................................................
...............................................................................................................
...............................................................................................................
Relative atomic mass (Ar) = .........................
(2)
(ii)
Use your answer to part (a)(i) and the periodic table on the Data Sheet to name metal
M.
The name of metal M is ...................................................................... .
(1)
(b)
The other metal oxide is iron(III) oxide.
This contains iron(III) ions (Fe3+) and oxide ions (O2-).
(i)
Explain in terms of electrons how an iron atom (Fe) can change into an iron(III) ion
(Fe3+).
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
Page 10 of 30
(ii)
The diagram below represents the electronic structure of an oxygen atom (O).
Complete the diagram below to show the electronic structure of an oxide ion (O2-).
(1)
(Total 6 marks)
Q6.
Hydrogen chloride (HCl) can be made by the reaction of hydrogen (H2) with chlorine (Cl2).
(a)
The diagrams represent molecules of hydrogen and chlorine.
Draw a similar diagram to represent a molecule of hydrogen chloride (HCl).
You need show only the outer energy level (shell) electrons.
(1)
Page 11 of 30
(b)
The word equation for the reaction of hydrogen with chlorine is shown below.
hydrogen + chlorine → hydrogen chloride
Write a balanced symbol equation for this reaction.
.....................................................................................................................................
(2)
(c)
Hydrogen chloride gas reacts with magnesium to form the ionic compound called
magnesium chloride. Use the table of ions on the Data Sheet to help you to write the
formula of magnesium chloride.
.....................................................................................................................................
(1)
(d)
Why does magnesium chloride have a much higher melting point than hydrogen chloride?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 6 marks)
Q7.
Pure carbon can exist in two forms, diamond and graphite.
(a)
Complete the diagram to show the electronic structure of a carbon atom.
A carbon atom has 6 electrons.
Show the electrons as crosses (x).
(1)
Page 12 of 30
(b)
A drill bit is used to cut holes through materials. The cutting end of this drill bit is covered with very
small diamonds.
By Wanderlinse [CC By 2.0], via Flickr
(i)
What property of diamond makes it suitable for use on the cutting end of a drill bit?
...............................................................................................................
(1)
(ii)
Explain, as fully as you can, why diamond has this property. Use your knowledge of
the structure and bonding of diamond and the information shown opposite to help
you to answer this question.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(3)
Page 13 of 30
(c)
Explain why graphite is a good conductor of electricity and why diamond does not conduct
electricity.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(Total 8 marks)
Q8.
Silicon is an extremely important element. More than a million tonnes of silicon are produced
each year. Silicon is made by reducing silicon oxide (sand) with carbon (coke).
(a)
(i)
Complete the diagram below to show the arrangement of electrons in an atom of
silicon. The Data Sheet may help you with this question.
(2)
(ii)
Which electrons in the silicon atom take part in chemical reactions with other atoms?
..........................................................................................................................
..........................................................................................................................
(1)
(iii)
What features of all the atoms of the elements in group 4 of the Periodic Table might
give them similar chemical properties?
..........................................................................................................................
..........................................................................................................................
(1)
Page 14 of 30
(b)
Silicon is difficult to classify as a metal or a non-metal because it has properties which
resemble both. Some of the properties of silicon are listed below.
•
•
•
•
•
•
•
•
Silicon is a shiny blue/grey solid.
Silicon is placed in Group 4 of the Periodic Table.
Silicon has a relative atomic mass of 28.
Silicon has a very high melting point (1410ºC).
Silicon has a very high boiling point (2355ºC).
Silicon conducts electricity.
Silicon oxide will neutralise alkalis.
Silicon forms compounds in which the silicon atoms are bonded to other atoms by
covalent bonds.
(i)
Select two properties from the list above in which silicon resembles a metal.
1. .....................................................................................................................
2. .....................................................................................................................
(2)
(ii)
Select two properties from the list above in which silicon resembles a non-metal.
1. .....................................................................................................................
2. .....................................................................................................................
(2)
(Total 8 marks)
Page 15 of 30
Q9.
This question is about calcium hydroxide.
Ancient artworks and monuments can be protected from acid rain if the surface is sprayed with
calcium hydroxide nanoparticles.
By Svilen Enev (Own work) [GFDL or CC-BY-SA-3.0], via Wikimedia Commons
(a)
Calcium hydroxide has the formula Ca(OH)2
Why are there two hydroxide ions for each calcium ion in the formula?
........................................................................................................................
........................................................................................................................
........................................................................................................................
(1)
(b)
The calcium hydroxide is used in the form of nanoparticles.
What are nanoparticles?
........................................................................................................................
........................................................................................................................
(1)
Page 16 of 30
(c)
A student added water to calcium oxide to make calcium hydroxide.
The equation for the reaction is shown below.
CaO + H2O → Ca(OH)2
Calculate the maximum mass of calcium hydroxide which could be made from 2.00 g of
calcium oxide.
Relative atomic masses (Ar): H = 1; O = 16; Ca = 40.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
Maximum mass of calcium hydroxide = ............................... g
(3)
(Total 5 marks)
Page 17 of 30
M1.
(a)
(i)
B
1
(ii)
A
1
(iii)
C
1
(b)
D and E
1
(c)
electron
1
[5]
M2.
(a)
1 / one
1
(b)
(i)
protons
1
(ii)
neutrons
1
(iii)
7
1
(c)
(i)
losing
1
(ii)
a positive
1
(iii)
electrostatic
1
(d)
high melting points
1
strong bonds
1
(e)
(i)
58.5
1
(ii)
mole
1
Page 18 of 30
(f)
very small (particles) or
ignore tiny / small / smaller / microscopic etc.
1-100nm in size or
(particle with a) few hundred atoms
1
[12]
M3.
(a)
oxygen and water
both needed for mark
allow hydrogen oxide for water
in any order
ignore formulae
1
(b)
(i)
best fit line, omitting point at 10s
straight line drawn through all correct points
1
(ii)
circle around point at 10 s
allow any indication
1
(iii)
7.5
allow ecf from candidate’s line
1
(iv)
increases (with time)
accept goes from 0 to 12.5
1
(c)
(i)
higher
1
(ii)
more concentrated
1
(d)
(i)
share
1
(ii)
covalent
1
(iii)
simple molecules
1
(e)
Water has a boiling point of 100°C
1
Water has a melting point lower than room temperature
1
[12]
Page 19 of 30
M5.
(a)
(i)
65
correct answer with or without working = 2 marks
if answer incorrect
evidence of (81 - 16) for 1 mark
ignore units
2
(ii)
zinc
accept error carried forward from (a)(i)
allow correct symbol
answer given should be element / metal closest to their answer
do not allow compounds
1
(b)
(i)
•
it loses electrons
sharing / covalency = max 1 mark
1
•
three electrons
1
(ii)
8 electrons shown in second shell.
accept dots / crosses / mixture of dots and crosses / e
electrons do not need to be paired
do not allow extra electrons in first shell
1
[6]
M6.
(a)
bonding pair in the overlap and 6 other electrons arranged around the chlorine
must have either circles or symbols
need not be pairs but must not be in the overlap region
accept without H and Cl if clear
accept all x’s or all o’s
1
Page 20 of 30
(b)
H2
+
Cl2
→
2HCl
accept multiples or fractions
accept correct formulae but not balanced for 1 mark
correctly balanced equation containing
‘correct’ lower / upper case symbols gets 1 mark
2
(c)
MgCl2
accept Mg2+(Cl-)2
1
(d)
because magnesium chloride is made of ions or is ionic
accept there are strong forces of attraction between the ions /
particles in MgCl2 or strong electrostatic attractions
accept more energy to separate particles in MgCl2
do not accept MgCl2 molecules
do not accept reference to breaking bonds
1
hydrogen chloride is made of molecules or is covalent
accept there are only weak forces of attraction (between the
particles / molecules) in HCl
do not accept weak covalent bonds
do not accept reference to breaking bonds
do not accept MgCl2 is a solid and HCl is a gas
1
[6]
M7.
(a)
2,4 (drawn as crosses) on shells
accept dots / e / - etc.
1
(b)
(i)
hard
allow rigid / high melting point
do not allow references to bonding
ignore strong
ignore unreactive
ignore structure
1
Page 21 of 30
(ii)
any three from
max 2 if ionic / metallic / molecule / intermolecular bonds or
incorrect number of bonds
•
giant structure / lattice / macromolecular
allow many bonds
•
covalent (bonds)
•
(covalent) bonds are strong
accept needs lots of energy to break bonds (owtte)
•
(each) carbon / atom forms four bonds
or
(each) carbon / atom bonded to four other atoms
3
Page 22 of 30
(c)
any three from:
max 2 if ionic / ions / metallic / molecule
‘it’ needs to be qualified
graphite
•
has delocalised / free electrons
do not accept the electrons move unless qualified (around
structure etc)
or
electrons that can move through / around the structure
•
each carbon is joined to three other carbon atoms
allow graphite has three bonds
or
one electron from each atom is free / delocalised
diamond
•
has no free / delocalised electrons
do not accept the electrons do not move
or
no electrons that move around the structure
•
all the electrons are used for bonding
allow diamond has 4 bonds
or
each carbon joined to four other carbon atoms
3
[8]
M8.
(a)
(i)
14 electrons =
gets 1 mark
2.8.4 =
gets 2 marks
2
(ii)
outer shell electrons
1
(iii)
same number of electrons in outer shell
1
Page 23 of 30
(b)
(1)
shiny
conducts electricity
(2)
oxide neutralises alkalis
covalent bonds
4
[8]
M9.
(a)
because calcium is +2 and hydroxide is –1
accept to balance the charges
or
to make the compound neutral (in terms of charges)
allow calcium needs to lose 2 electrons and hydroxide needs to
gain one electron
1
(b)
particles of size 1-100 nm
allow clear comparison to ‘normal’ size particles
or particles with a few hundred atoms / ions
or particles with a high surface area (to volume ratio)
or as different properties to ‘normal’ size particles of the same substance
1
(c)
M r CaO = 56
and
M r Ca(OH)2= 74
1
2/56 (x74) or 0.036 (x74)
or
allow ecf from step 1
74/56 (x2) or 1.3(214…) (x2)
1
2.6(428…) in range 2.6 to 2.96
correct answer with or without working gains 3 marks
allow ecf carried through from step 1
ignore final rounding to 3
1
[5]
Page 24 of 30
E1.
(a) Were well answered with students being able to interpret the information given in the
atomic structure diagrams.
(b)
Were well answered with students being able to interpret the information given in the
atomic structure diagrams.
(c)
Protons and neutrons were the most common incorrect responses given for a particle with
a negative charge.
E2.
(a) These question was generally well answered. The group number for lithium and sodium
was usually correctly given as 1.
(b)
Generally well answered question. A common incorrect answer for the mass number of
lithium was 3.
(c)
(i)(ii) The majority of students successfully interpreted the diagram to correctly answer
parts (i) and (ii). Some wild guesses were evident.
(iii)
The identification of the correct forces in this part posed most problems. A significant
number of students chose one of the wrong options.
(d)
This question differentiated well. Only the more able students scored full credit.
(e)
(i)
(f)
The idea of the magnitude of nanoparticles being ‘very small’ was well understood.
However, a significant number of students still refer to them as being microscopic, tiny or
small, or make a comparison with normal particles by describing them as being smaller.
There were also irrelevant references to the taste and flavour imparted by the particles.
E3.
(a)
(b)
Common incorrect answers were obtained by subtracting the relative atomic
masses to give 12.5 or by their product to give 816.
Hydrogen and hydroxide were common incorrect answers.
(i)
Many students showed they understand the meaning of the term ‘line of best fit’.
Unfortunately a significant number of students drew random straight lines, some
missing points out and others including the anomaly.
(ii)
A few students circled the wrong point or did not attempt the question.
(iii)
Reading the scale on the y axis was a problem for many students with incorrect
answers such as 5, 5.5, 7 and 8 common. The majority of students realised that the
volume of oxygen increased in (iv).
Parts (c), (d) and (e) were generally well answered.
Page 25 of 30
E5.
(a)
(b)
E6.
(i) A very good number of the candidates gained both marks for this question and
showed a good understanding of the meaning of the relative formula mass. One
mark was allowed for evidence of correct working, i.e. 81-16, if the final answer was
incorrect e.g. 75. A common incorrect answer was 97.
(ii)
Error carried forward was allowed from part (a)(i) to part (a)(ii) and many of the
candidates gained this mark. Technetium and molybdenum scored credit for 97
using error carried forward from part (i). Some of the candidates confused relative
atomic mass with atomic number when using the periodic table. Thallium was a
common incorrect answer, even when part (i) was correct, which showed a lack of
understanding of the difference between atomic mass and formula mass.
(i)
This part proved difficult for many of the candidates. The mark scheme gave one
mark for the idea of the iron atom losing electrons and one for the idea that three
electrons are involved. A fair number of candidates gained one mark for the idea of
electrons being lost by an iron atom but fewer candidates realised that 3 electrons
were lost. Some confused answers referred to sharing electrons and covalency and
iron ions losing electrons. Some candidates thought that protons or ions were
transferred and that oxygen gave electrons to the iron atom, which showed a lack of
understanding.
(ii)
The mark here was gained by a fair number of candidates. Many candidates
completed the diagram by drawing 4 or 6 electrons in the outer shell instead of 8. A
minority of candidates inserted extra electrons into the inner shell and were
penalised.
Foundation Tier
Perhaps not surprisingly this question proved extremely difficult to Foundation tier candidates
since much of this work was previously only examined at Higher tier. It is pleasing to note,
however, that despite the difficulty of the question the vast majority of the candidates attempted
all parts and did not give up.
(a)
Only the more able candidates were able to draw the hydrogen chloride molecule.
(b)
Few candidates gained marks for this part. A common incorrect answer was H + Cl → HCl.
(c)
This was not as well answered as was expected. The candidates gave a variety of
answers such as Mg2Cl and Mg2Cl2. A number of candidates attempted to write an
equation for the reaction in which MgCl2 is formed. This was accepted providing the
formula of MgCl2 was correct.
(d)
This part was very poorly answered. Answers such as ‘the bonds between the
magnesium chloride molecules are stronger than those between the hydrogen chloride
molecules’ or ‘the ionic bonds in magnesium chloride are stronger than the covalent bonds
in hydrogen chloride’ were frequent and revealed a lack of understanding of this topic. A
variety of answers was accepted for this question. A simple answer such as ‘magnesium
chloride is an ionic compound whereas hydrogen chloride is molecular’ gained two marks.
Page 26 of 30
Higher Tier
This question discriminated well between the candidates.
(a)
Most candidates successfully drew the electron arrangement in hydrogen chloride.
(b)
This part was usually well answered. Weaker candidates wrote H and Cl instead of H2 and
Cl2.
(c)
Writing the formula of magnesium chloride was a good discriminator. Even some
candidates who wrote down the correct ions were unable to successfully combine them
together. Candidates must realise the importance of upper and lower case letters when
writing symbols and formulae; CL2 and HCL received no credit.
(d)
Most candidates recognised the importance of the ionic nature of magnesium chloride but
then many candidates went on to state that it has stronger intermolecular forces. Popular
incorrect ideas centred either on two bonds to be broken rather than only one in hydrogen
chloride, or that magnesium is more reactive than hydrogen or that covalent bonds are
weaker than ionic. Other candidates failed to mention hydrogen chloride at all.
Page 27 of 30
E7.
(a) Almost all of the candidates gained the mark in this part. Diagrams were generally clear
although a few candidates attempted to correct mistakes by crossing out their crosses! It
was often difficult for the examiner to adjudicate as to what was crossed out in these
diagrams. Errors included four electrons on the first shell and two on the second and two
on the first shell and six on the second.
(b)
(ii)
Many of the candidates did not appreciate that it is the hardness of the diamonds that
makes them particularly suitable for cutting tools rather than their strength. A few
candidates gave high melting point which was accepted as an alternative to
hardness.
Most of the candidates were able to gain some of the marks but few gained all three.
Some very good answers were seen which linked the structure and bonding in
diamonds to their hardness but the question also revealed some misconceptions. A
surprising number of candidates thought that the number of bonds made by each
carbon atom is three despite the diagram on the previous page of the question
paper. Candidates should be encouraged to make full use of the information given in
the questions. The bonding in diamonds was variously described as ionic or metallic
whilst others thought that the intermolecular bonds in diamond are very strong.
These misconceptions limited the number of marks available to the candidate. Many
vague answers were seenwhich linked hardness to the compactness of the
structure or to it having a tight structure, and such answers did not gain credit.
(c)
This part was similar to part (b)(ii) in that few candidates gained all three marks whereas
many gained one or two.
The mark scheme contained four main marking points, two relating to graphite and two
relating to diamond. The four main marking points are listed below:
Graphite
•
Has delocalised electrons (We also accepted it has free electrons or it has
electrons that can move through or around the structure. We did not accept
the statement, the electrons can move, since this is true of all electrons
whether or not delocalised.
•
Because each carbon is joined to three other carbon atoms or one electron
from each atom is delocalised.
Diamond
•
Has no delocalised / free electrons (We did not accept, the electrons do not
move, for the same reasons as above.)
•
Because each carbon atom is joined to four other carbon atoms or because all
of the electrons are used for bonding.
The candidates were able to score any three of the four marking points. Many candidates
were able to gain two marks, for identifying that graphite hasdelocalised electrons whereas
diamond does not, but few were able to explain why in terms of the number of bonds
formed by each carbon atom or the use of electrons in bonding.
A number of candidates lost a mark because they only referred to graphite in their answer
and made no comment about diamond. As in part (b)(ii) the question revealed many
misconceptions. Some candidates gave an excellent description of why metals conduct
electricity in terms of positive ions in a sea of electrons rather than the reason for
graphite’s conductivity. Other incorrect responses included ideas such as, it conducts
electricity because the layers can slide over each other or it conducts electricity because it
is a metal.
Page 28 of 30
E9.
(a) Some of the most able students were able to deduce or refer to the Chemistry Data
Sheet to find the charges on the calcium and hydroxide ions. Other able students
answered in terms of loss and gain of electrons. Some students referred to calcium
gaining electrons from hydroxide or to covalent bonding and the sharing of electrons or to
the balancing of an equation, rather than balancing charges.
(b)
Responses which quantified the size of nanoparticles as 1-100 nm or a few hundred
atoms, or which related to their high surface area to volume ratio, or different properties to
“normal” size particles were credited. Approximately half of the students gained credit.
Those who did not gain credit often gave imprecise responses such as very small or tiny.
(c)
A large number of students gained 3 marks, and a substantial minority gained just the first
marking point. Commonly seen errors included incorrect calculation of the Mr of Ca(OH)2
(eg 72), or dividing 56/74 rather than 74/56. Another common error was to find the Mr of Ca
(OH)2 and multiply by 2.
As always a variety of methods were employed by candidatesstudents, all of which were
credited appropriately for their success.
Page 29 of 30
Page 30 of 30