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MINISTRY OF EDUCATION
FIJI SCHOOL LEAVING CERTIFICATE
EXAMINATION
2011
CHEMISTRY
COPYRIGHT: MINISTRY OF EDUCATION, REPUBLIC OF THE FIJI ISLANDS
2.
MINISTRY OF EDUCATION
FIJI SCHOOL LEAVING CERTIFICATE EXAMINATION – 2011
EXAMINER’S REPORT
CHEMISTRY
GENERAL COMMENTS
The 2011 paper followed a similar format as other Chemistry papers of the past years. 4221 candidates sat
for the paper and the overall pass rate based on the raw marks is not very encouraging.
Teachers are urged to take heed of the following comments given in this report so that candidates are
prevented from making the same errors.
While teaching Chemistry, it is good to always revise earlier work on the related topics being
taught. During revision/remedial, Form 5 coverage should not be neglected.
Practical work forms an integral part of the theory being taught. In some cases it was obvious
that practical work was not done.
During the practical work, safety rules, precautionary measures, sources of errors and
correction of these errors should also be enforced/emphasised. Candidates should be able
to identify apparatus correctly and be able to know its correct use.
When writing a chemical equation, candidates should be able to complete and balance it
correctly.
Candidates must refrain from writing two or three responses when only one is required.
Many candidates are still not following instructions correctly hence losing marks.
Candidates must follow instructions by writing the correct name or formula of a chemical
when required.
Candidates must not use pencil except when drawing diagrams.
In some cases candidates did not provide answers as per mark allocation, hence running
out of time.
Use of “twink” or “white ink” should be avoided as this smudges the answers which
were written.
Candidates should write neatly and legibly with words correctly spelt.
The Examiner’s Report should be used by teachers to guide them during teaching, revision and for
remedial purposes.
3.
SECTION A
The responses given in a random sample of 100 scripts are tabulated below. The correct response in each
case is marked by an asterisk(*).
Question
number
A
B
C
D
No
Response
1 20 17 54 * 8 1
2 6 32 9 52 * 1
3 44 0 42 * 14
4 57 * 26 11 6
5 34 47 * 10 6 3
6 32 13 46 * 8 1
7 11 47 * 29 12 1
8 14 38 * 40 8
9 38 14 15 32 * 1
10 33 * 17 41 8 1
11 18 27 35 20 *
12 22 * 11 53 14
13 42 12 11 34 * 1
14 5 15 19 61 *
15 16 33 * 42 9
16 36 9 24 31 *
17 14 65 * 6 14 1
18 37 * 26 28 7 2
19 29 * 3 56 11 1
20 9 30 37 * 23 1
Analysis of the randomly selected sample of 100 scripts indicated that some candidates did well in this
section. A few of them scored the full marks.
The following questions proved to be too difficult for many candidates: Q11, 12 and 19.
Questions 11 and 12 assessed concepts from organic chemistry where candidates had to identify the type
of reaction and provide the systematic name for the organic molecule.
4.
In Question 19, candidates were required to first, calculate the volume of the cube by using the value for
length given[ 2cm x 2cm x 2cm = 8cm3] then to divide by the mass [40 g] to calculate the cube’s density
D = M / V
= 40 / 8
= 5 g/cm3
Questions 8, 9, 10, 13, 15, 16, 18, and 20 proved challenging for many of the candidates.
Questions 8, 9 and 10 were based on Inorganic Chemistry and as in the past years this topic was still not
answered well in the exam. Periodic trends of oxides and chlorides across the periodic table must be
understood.
Many candidates chose option A as their answer in Question 13 thinking that the two molecules were
isomers. Candidates should be able to work out if two organic molecules are isomers or if they belong to
the same homologous series. Teachers need to guide students on how to determine isomerism of two or
more molecules.
Questions 15 and 16 tested concepts from Physical Chemistry. Candidates had difficulty interpreting the
energy curve and applying the Le Chatelier’s Principle.
In Question 18, candidates had difficulty in calculating the oxidation number of Bromide ion[Br-] in the
reaction given, hence could not determine whether it had been oxidised or reduced.
Calculating the number of molecules in one mole of carbon dioxide gas as in Question 20 was challenging
for many candidates.
SECTION B
QUESTION 1
(a) (i) Well done. Incorrect responses were for the last two steps, that is, 2,4,3,1 instead of
2,4,1,3.
(ii) Poorly done.
Step 1: Common incorrect response was “to get all the solution into the flask”.
Step 3: Common incorrect response was “to dissolve all the sodium carbonate” and “so
that the correct measurement is known”.
(b) (i) – (iii) Well done.
5.
(iv) Some candidates had difficulty in calculating the number of moles because they had made
the error of using the incorrect Mr which in turn obtained the incorrect mole ratio and hence
the incorrect empirical formula.
QUESTION 2
(a) (i) Poorly done. Common incorrect responses to purpose of adding sand to
calcium carbide were “increase in surface area” or to “distribute heat evenly.”
(ii) Well done. However, some candidates mistook the formula for ethyne by incorrectly
writing C2H4 instead of C2H2.
(iii) Very poorly done. Common incorrect responses such as writing uses of esters, “cooking”.
Many candidates did not know that ethyne gas is used as a fuel in the oxyacetylene torch
for welding and cutting of metals.
(b) (i) Well done. Many candidates knew that the function of the porous pot was to distribute heat
evenly.
(ii) Fairly attempted. Many candidates wrote the incorrect formula for ethanol hence giving
the wrong products.
(iii) Poorly done. Common incorrect response was “burns with a pop sound” or “relights a
glowing splint”.
(iv) Good attempt. A common incorrect response was “carry out lab in a fume cupboard”.
Teachers need to emphasise to the students the difference between general laboratory
safety rules and precautionary measures with respect to the experiment being carried out.
For example, ethanol is not to be heated directly as it is flammable therefore the use of
broken porous pot.
6.
QUESTION 3
(a) Very poorly done. Two of the reactions were carried out in Form 4 and repeated in Form 5
however, candidates could not attempt this question correctly.
Common incorrect responses:
Reaction Observation Product
Shiny iron nail placed in copper
Sulphate solution
“Iron nail will rust” Name did not correspond to
observation stated.
Sulphur dioxide is bubbled
through potassium permanganate
solution
“colour will decolourise” rather
than solution will change colour
from purple to colourless.
“Chromium ion.”
A piece of zinc metal is placed in
a test tube of dilute hydrochloric
acid
Well done. Some wrote
“hydrogen gas forms” which was
in correct.
Poorly done. Incorrect response
given for the correct observation.
(b) (i) Poorly done. Teachers need to explain to students the difference between
stating an observation of an experiment and stating the name of the product formed. Many
candidates stated the name of the product formed instead of stating the observation made at
the anode.
(ii) Poorly done. Writing and balancing of ion-electron half equation proved challenging for
many of the candidates.
(iii) Poorly done. The important application of the electrolysis of molten sodium
chloride was not known to many. Common incorrect response “for electroplating” or “for
electrolysis” or “conduction of electricity”.
QUESTION 4
(a) (i) Well done.
(ii) Writing and balancing of the chemical equation again proved challenging for many of the
candidates.
(b) (i) Well done. Some common incorrect responses were: writing the formula instead of
writing the name.
(ii) Satisfactorily attempted. The test for hydrogen gas was not described well.
Common incorrect response were “glowing splint goes off with a pop sound” or just “pop
test” instead of “burning splint goes off with a pop sound”.
7.
(iii) Poorly done. The colour of chlorine gas was not known to many candidates common
incorrect response were “green” or “yellow”.
(c) (i) Poorly done. Most of the candidates explained the particle model in a solid as
their response which was incorrect. Ice has an open cage-like structure
which is why there is an increase in the volume of water when frozen.
(ii) Poorly done. Very few candidates wrote surface tension as the correct answer. This
important concept of water is taught in Form 5 and is also covered in one of the
experiments for practical class. It was evident that those who did the experiment were able
to answer the questions correctly.
(iii) Poorly done. Common incorrect response were “added weight to water
spreads the droplet” or “soap is denser than water” or “soap is soluble in
water”.
QUESTION 5
(a) (i) Fairly attempted. Many candidates were able to calculate the average volume correctly
but had difficulty rounding off the answer correct to 1 significant figure which was 10mL.
(b) (i) Satisfactorily attempted. Common incorrect response B was “changing of
state”. Candidates need to be taught not to give vague but specific responses.
(ii) Good attempt. Some common incorrect response was 75oC instead of 25
oC.
(iii) Good attempt. However, many candidates did not know that all the naphthalene had
solidified.
(c) (i) Fairly attempted. Common incorrect response was “rhombic sulphur”
instead of plastic or monoclinic.
(ii) Well done.
(d) (i) Well done. A common incorrect response was “distillation”.
(ii) A - Poorly done. Common incorrect response was “burette”.
B - Very well done.
8.
SECTION C
QUESTION 1
(a) (i) Well done.
(ii) Well done although many candidates incorrectly wrote the name instead of the
symbol hence they lost marks.
(iii) Poorly done. The term diatomic was not understood. Diatomic molecules are
molecules composed of only two atoms of either the same or different chemical
elements. Chlorine is an element that can exist as a diatomic molecule.
(iv) The trend in electronegativity across the periodic table was not
known/properly understood which was why candidates did very poorly in this
question.
(v) Fairly attempted. Many candidates could not explain the reason for their
correct answer in silicon which was strong covalent bonds between silicon
atoms.
(b) (i) Poorly done. Although a repeated question from past years’ examination, still
candidates were writing incorrect responses because they had failed to
understand the question. Common incorrect answer was “cancellation of charges”
instead of cancellation of polarity”. Candidates must also mention the shape
of the molecule which was symmetrical.
(ii) Very poorly done. The explanation for graphite was well done. However,
some candidates did mention weak van der Waal’s forces of attraction but failed to
mention that this attraction is present between the layers.
For diamond, candidates were expected to write network of strong covalent
bond between carbon atoms.
(iii) Satisfactorily attempted. Common incorrect response was “NaCl is ionic
instead of polar”. Some wrote “like dissolves like” rather than being specific
about the polarities of the solvents.
(iv) Satisfactorily attempted. The correct response is that there are strong ionic bonds in
magnesium oxide and weak van der Waals forces between the CO2 molecules.
(c) Not well attempted. Even though the candidates knew the correct shapes of the
molecules, drawing of the Lewis structures was poorly done. Candidates were still
committing the error of drawing the structural formula or a mixture of both where lines
were used to show the bonds therefore losing marks.
9.
QUESTION 2
(a) (i) Well done.
(ii) Well done.
(b) Poorly done. Many candidates did mention the equal repulsion between the bonding
pairs but failed to mention that there are four bonding pairs in methane molecule.
(c) (i) Well done.
(ii) Well done. Some candidates were writing the incorrect formula for ethanoic
acid and sodium ethanoate.
(iii) Poorly done. Common incorrect responses were “pink”, “colourless” and not
pale/light pink.
(iv) I. Poorly done. Common incorrect response, “rinse with distilled water
and the solution it is to contain”. Candidates should have mentioned that
after rinsing with distilled water the burette is to be rinsed with sodium
hydroxide solution.
II. Some failed to write rinse with distilled water. Common incorrect
response “rinse with water”.
(v) Well done.
(vi) Well done by most of the candidates. Common incorrect answer was “to use
15ml as the volume instead of 25ml” or “not converting the volume to litres”.
(vii) Poorly done. Candidates could not relate their findings to make a conclusion.
QUESTION 3
(a) Well done. Candidates were able to calculate the correct empirical formula hence the
correct molecular formula. However, some failed to take oxygen into consideration.
(b) (i) Well done.
(ii) Well done. Some of the candidates failed to use the mole ratio of 4Fe : 2Fe2O3 from the
balanced equation given.
(iii) Fairly well done. Many candidates worked out the Mr for 2 moles of iron(II) oxide which
came to 320g when it should have been 160g, hence they lost marks.
10.
(c) (i) I – poorly done. Most common incorrect answer was “simple molecular”,
“molecular” or “giant ionic”.
II – well done. Many candidates knew that the nature of Al2O3 is amphoteric.
(ii) Very poorly done. Many candidates did not answer what was asked.
Many of them wrote balanced chemical reactions for the formation of the oxides
instead of the reaction of the oxide with water which was required. Some candidates
wrote descriptive explanations with no chemical equations thus lost marks.
(d) This question was poorly done. The full description was required. Some candidates
lost marks for incomplete responses. In some cases, the correct description of the
change was written without naming the new product and vice versa. Various
colours of precipitate were mentioned for (ii), (iii) and (iv). It was evident that
candidates did not know the application of solubility rules. This concept needs to
be taught well at Form 5 and revised again thoroughly in Form 6.
(i) Poorly done. Most common incorrect response “Blue precipitate forms” when it
should have been a blue solution of copper sulphate forms.
(ii) Poorly done.
(iii) Poorly done.
(iv) Poorly done.
QUESTION 4
(a) This question on Organic Chemistry was fairly attempted. Although, similar
questions had appeared in past years, it was disheartening to note that candidates
were still committing the same errors. E.g use of an ester – students are still finding
this difficult to answer correctly.
(i) Satisfactorily done. Many candidates were confused in identifying
Compound E which was polythene and not PVC.
(ii) Reaction 1: Poorly done. Common incorrect response “addition”
instead of polymerisation. Teachers need to explain to the students the difference
between the type and the name of a reaction .
Reaction 2: Well done.
11.
(iii) Very poorly done. Few weaknesses to take note of are:
Odd numbers of carbon atoms in the long chain
There was no indication of continuity in the long chain therefore some drew the
structure of butane.
There were some structures which had only two carbon atoms.
Some candidates drew the structure of PVC.
(iv) Not well attempted. Few candidates were able to identify Gas X correctly as carbon
dioxide.
Use of Compound D was a challenge for some of the students. Many of the candidates did
not know the uses of esters.
(b) (i) Well done. The most common incorrect response was “chlorine is less
dense than air”.
(ii) Poorly done. Many of the candidates did not understand that chlorine when bubbled
through water turns blue litmus to red and this is due to the formation of the two acids.
Most incorrect response “chlorine is acidic”.
(c) (i) Well done. Some candidates incorrectly wrote Bauxite as the chemical name.
(ii) Poorly done. There is a need for teachers to teach the advantages and disadvantages
of all materials used in any industrial production. The disadvantage of using molten
cryolite is that it produces pollution in the form of fluoride compounds.
(iii) Poorly done. Only a few candidates knew that graphite reacts with the oxygen gas
to form carbon dioxide therefore the graphite anode has to be replaced from time to time.
QUESTION 5
(a) (i) and (ii) Well done. However, candidates must be reminded to write complete answers. Many
of them gave their reasons as “highest concentration” without mentioning the
chemical they were referring to.
(iii) Well done. Some candidates failed to start from zero[0] on the graph.
(b) (i) Very poorly done. Most of the candidates wrote that energy is released or that
it was an exothermic reaction.
Teachers need to teach the concept of thermochemical equations and what it
means. Thus, ∆ H = -120kJ mol-1
means that 120kJ of energy is released/
evolved when 2 moles of AB2 is broken down to form 1 mole of A2B4.
12.
(ii) Fairly attempted.
I & II. Many candidates stated that the forward reaction would be favoured but did not
mention the effect this would have on the amount of A2B4. Hence,
losing half mark.
(iii) Poorly done. Many candidates could not apply their knowledge of the Le Chatelier’s
principle to the exothermic reaction in question.
(c) Poorly done. Very few candidates understood the concept of Bronsted-Lowry Theory
of acids and bases. Common incorrect formula in (i) was HNO3- although the name
was correct.
SECTION D
QUESTION 1 CONSUMER CHEMISTRY
The least popular choice and was poorly done.
(a) (i) – (iv) Poorly done. Candidates failed to identify the saponification process and to write
and complete the word equation.
(b) (i) – (iii) Poorly done. The name and the formula of propylene was attempted
poorly.
(c) (i) – (iii) The reactions of chlorine was not understood and these were poorly
attempted.
(d) (i) – (iv) This matching question was poorly done.
13.
QUESTION 2 CHEMISTRY OF FOOD
The third [3rd
] most popular choice.
(a) Well done. However, the most incorrect response was to interchange the properties of butter
with that of margarine.
(b) (i) Linking the two amino acids was challenging for the candidates. The structure
of the molecule formed was incorrect.
(ii) Circling of the peptide bond was poorly done as other bonds were included.
However, naming of this special bond as peptide bond was well done.
(iii) Naming of water as the other product formed during this reaction was well
done. However, some candidates did not take heed of the instruction in the question
and wrote the formula of water instead of the name hence losing marks.
(iv) Well done. Some candidates incorrectly stated their response as hydrogenation.
(c) Matching was well done.
(d) (i) Well done.
(ii) Poorly done as some candidates failed to combine the two molecules
together.
(iii) Well done.
(e) Poorly done. The correct response was not written by most of the candidates.
QUESTION 3 CHEMISTRY IN THE ENVIRONMENT
This question was the second [2nd
] most popular choice.
(a) (i) Well done.
(ii) Poorly done. Common incorrect response was “poison the seawater” or kills
marine organisms. Candidates were expected to write blockage of waterways,
increase in BOD and support aquatic plant growth to name a few.
(iii) Well done.
(b) (i) Poorly done. Many candidates did not know that the person will be exposed to
lead in the paint.
(ii) Causes liver and kidney failure or inhibition of enzyme action. Many candidates
incorrectly stated the effects of lead in humans as cancer.
14.
(c) (i) Well done.
(ii) Well done.
(d) (i), (ii) Poorly done. Very few candidates were able to get both the name of the
pollutant as well as the equation correct.
(e) Well done. Many candidates wrote superphoshate in place of rock phosphate and copper
in place of lead.
QUESTION 4 CHEMISTRY OF COPPER AND ITS COMPOUNDS
This question was the most popular choice.
(a) (i) Poorly done. Many of the candidates mentioned only the colour and did not
state the formation of the precipitate.
(ii) Poorly done. Candidates just wrote the formula of the complex ion. Writing
and balancing of the chemical equation was challenging.
(iii) Naming of the complex ion was very poorly done. The oxidation state of
copper was not stated in the name of the complex ion hence candidates lost
a mark.
(b) (i) Well done.
(ii) Well done.
(iii) Poorly done. Correct industrial use is in electrical wiring and as water pipes.
(c) Well done. This matching question was well attempted.
(d) Very poorly done. Candidates were expected to calculate the number of moles of
water correctly as 0.062 moles then to use the balanced chemical equation given to
determine the mole ratio which was 1 : 1
(e) Well done. Brass is preferred to copper because brass has high tensile strength,
is cheaper and is more resistant to corrosion.
THE END