MINISTRY OF EDUCATION

FIJI SCHOOL LEAVING CERTIFICATE

EXAMINATION

2011

CHEMISTRY

COPYRIGHT: MINISTRY OF EDUCATION, REPUBLIC OF THE FIJI ISLANDS

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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.

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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.

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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.

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(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.

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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”.

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(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.

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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.

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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.

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(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.

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(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.

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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.

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(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

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