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FIJI SCHOOL LEAVING CERTIFICATE EXAMINATION 2010

CHEMISTRY

Time Allowed: Three Hours

(An extra ten minutes is allowed for reading this paper.)

INSTRUCTIONS

1. Write all your answers in the Answer Book provided.

2. Write your Index Number on the front page and inside the back flap of the Answer Book.

3. If you require more paper, ask the supervisor for extra sheets. Tie these inside the

Answer Book at the appropriate places.

4. You may use a calculator, provided it is silent, battery-operated and non-programmable.

5. There are four sections in this paper. Sections A, B and C are compulsory. Note the choices in Section D.

Note: A Periodic Table of Elements is provided for your use during the examination. Both the atomic number and the relative atomic mass for each element are given.

SUMMARY OF QUESTIONS

Section Guidelines Total

Mark

Suggested Time

A There are twenty multiple-choice questions.

All the questions are compulsory.

20 30 minutes

B There are five short-answer questions.

All the questions are compulsory.

25 45 minutes

C There are five questions.

All the questions are compulsory.

45 87 minutes

D There are four questions.

Answer only one question.

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SECTION A

[20 marks] The multiple-choice questions are all compulsory. Each question is worth 1 mark.

INSTRUCTIONS FOR MULTIPLE – CHOICE QUESTIONS

1. In your Answer Book, circle the letter which represents the best answer. If you change your mind, put a line through your first choice and circle the letter of your next choice.

For example:

2. If you change your mind again and like your first answer better, put a line through your second circle and tick () your first answer.

For example:

3. No mark will be given if you circle more than one letter for a question.

1. The chemical compound that contains the greatest number of cations is

A. AlCl3

B. NaOH

C. Na2CO3

D. Mg(OH)2

2. Which one of the following substances listed below is a good conductor of electricity in the solid state?

A. iodine

B. graphite

C. diamond

D. sodium chloride

3. The type of bonds broken when iodine sublimes is

A. Van der Waals. B. metallic. C. covalent. D. ionic.

12 A B C D

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4. If there are 12 x 1023 molecules in 2 moles of NO2, how many atoms of oxygen will be

present in the 2 moles of NO2?

A. 6 x 1023 B. 12 x 1023 C. 24 x 1023 D. 48 x 1023

[Avogadro’s constant, NA = 6 x 1023 units/mole]

5. The equation for the combustion of ethene (C2H4) is shown below.

C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(g)

What is the amount (number of moles) of oxygen gas required for the complete combustion of 56 g of ethene?

A. 2

B. 3

C. 4

D. 6

6. What is the mass of solid sodium hydroxide required to prepare a 250 mL solution of concentration 0.2 mol L-1?

A. 2 g B. 6 g

C. 12 g

D. 50 g

7. The table shown below summarises information of elements X and Y.

Element Atomic

number

Mass number

X 12 24

Y 17 35.5

The molecular mass of the compound with the formula XY2 formed by the combination of

X and Y is

A. 41

B. 46

C. 60

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8. Which of the following pairs of oxides changes red litmus paper blue in aqueous solution?

A. MgO, SiO2

B. Na2O, MgO

C. SiO2, Al2O3

D. SO3, Na2O

9. The following three statements (I to III) were made about the reaction.

Na2CO3(aq) + Ca(OH)2(aq) 2NaOH(aq) + CaCO3(s)

I. The calcium carbonate can be removed by filtration. II. The type of reaction is precipitation.

III. Sodium carbonate is insoluble in water.

The correct statements about the reaction are

A. I and II. B. I and III. C. II and III. D. I, II and III.

10. The element with atomic number 3 is likely to have similar chemical properties to the element with atomic number

A. 4 B. 6 C. 8

D. 11

11. The conversion of ethene to ethane requires a catalyst. Which one of the chemicals listed below is the most suitable catalyst?

A. nickel

B. copper

C. manganese dioxide D. vanadium pentoxide

12. When a few drops of water are added to a lump of calcium carbide (CaC2) in a test tube, the

gas that is produced is

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13. The molecules CH3 – CH2 – CH2 – CH3 and CH3 – CH – CH3 are related in that they

CH3

A. are isotopes. B. are isomers.

C. have the same systematic name. D. have the same physical properties.

14. The systematic name of the compound

is

A. butan - 1 - ol.

B. 1 - methylpropan - 2 - ol. C. 2 - methylpropan - 2 - ol. D. 2 - methylpropan - 1 - ol.

15. The pH of a solution of potassium hydroxide with a concentration of 0.001 mo1 L-1 is

A. 10-11 B. 10-3 C. 3

D. 11

16. The condition that will probably not increase the rate of a reaction is

A. adding water to dilute the reaction mixture. B. increasing the temperature of the system. C. adding a catalyst to the reaction mixture. D. increasing the surface area of reacting particles.

17. In which of the following substances is the oxidation number of the nitrogen atom +5?

A. N2

B. NH3

C. HNO3

D. N2O4

Turn Over

CH3

H

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18. The diagram below represents energy changes during a chemical reaction represented by the equation: aX + bY cZ

What is the activation energy for the forward reaction?

A. 250 kJ

B. 400 kJ

C. 450 kJ

D. 600 kJ

19. During the electrolysis of molten magnesium chloride, the reaction occurring at the negative electrode will be

A. 2C1– Cl2 + 2e–

B. Mg Mg+2 + 2e– C. MgCl2 Mg + Cl2

D. Mg+2 + 2e– Mg

20. Aluminium metal is obtained by the electrolysis of a molten mixture of alumina (Al2O3) in

cryolite (Na3AlF6).

Why is cryolite added to the electrolytic cell?

A. to prevent the oxidation of the anode

B. to prevent the discharge of fluoride in the environment

C. to increase the melting point and the conductivity of the electrolyte D. to lower the melting point and increase the conductivity of the electrolyte

600 kJ

450 kJ

250 kJ 400 kJ

cZ

aX + bY

Reaction pathway 100

200 300 400 500 600

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SECTION B

[25 marks] The five questions in this section are all compulsory.

Each question is worth 5 marks.

Reminder: For the questions involving calculations, ensure that the working is shown and that the equations used in your answers are balanced.

QUESTION 1

(a) The set-up given below shows a simple method of preparing carbon dioxide gas. Study the diagram and answer the questions that follow.

(i) Name the apparatus labelled X. (½ mark)

(ii) Write one observation that will be made in test tube I as the hydrochloric

acid reacts with calcium carbonate. (½ mark)

(iii) As the carbon dioxide gas passes into test tube II, what change will take

place in the appearance of the lime water? (½ mark)

(iv) If the carbon dioxide gas is passed into the limewater in test tube II

for a longer time, what other change will take place? (½ mark)

(v) Complete the following equation in the Answer Book.

Ca(OH)2(aq) + CO2(g) + H2O(l) (½ mark) X

Limewater Dilute

Hydrochloric acid

Calcium carbonate

Test tube I

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SECTION B (continued)

(b) The following instructions for an experiment to study the difference in the properties of mixtures and compounds was given to a group of Form Five students.

(i) Give one important observation that would be made in:

I. Step 3

II. Step 4 (1 mark)

(ii) What is the chemical difference between samples A and B? (1 mark)

(iii) Complete the equation for the reaction taking place in Step 2 in the Answer Book.

Fe(s) + S(s) (½ mark)

QUESTION 2

(a) A student used the following set-up to investigate the reaction of calcium with water.

º

Step 1 Prepare sample A by thoroughly mixing 25 g of iron filings and 15 g of powdered sulphur.

Step 2 Heat 20 g of sample A in a crucible to produce sample B.

Step 3 Place a magnet wrapped in paper on sample A.

Step 4 Add 5 mL of dilute hydrochloric acid to sample B in a clean test tube.

º º

º

º º

º

gas

water

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(i) How would the student know that the test tube was full of gas? (½ mark)

(ii) Name the gas produced in the reaction. (½ mark)

(iii) The student took some solution from the beaker into a test tube and added 3 drops of phenolphthalein from a dropper.

State an observation the student will make. (½ mark)

(iv) Write a complete and balanced equation for the reaction between

calcium and water in the Answer Book. (1 mark)

(b) The following materials are given:

a 600 mL beaker

a steel key

nickel ammonium sulphate solution

connecting wire

2 dry cells

a strip of nickel

(i) In the space provided in the Answer Book, draw a labelled circuit

diagram showing the electroplating of the steel key with nickel. (2 marks)

(ii) State one importance of electroplating a metal. (½ mark)

QUESTION 3

Washing soda crystals or hydrated sodium carbonate can be represented by the formula Na2CO3 . x H2O

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STEPS WEIGHING BALANCE

READINGS

1. A clean dry crucible and lid were weighed.

2. Some washing soda was added to the crucible. The crucible and the contents were then reweighed.

3. Crucible and contents were heated gently at first and then strongly for 10 minutes. It was then allowed to cool before being reweighed.

4. The crucible and contents were

heated for a further 5 minutes, then allowed to cool before being

reweighed.

5. The crucible and contents were re- heated and re-weighed until a

constant mass of ± 0.05 g was achieved.

(a) Explain how the student will know that all the water in the hydrated sodium

carbonate sample have been completely driven out. (1 mark)

(b) Determine the mass of:

(i) hydrated sodium carbonate used (½ mark)

g

60.1 60.2 60.3

74.4 74.5 74.6

65.4 65.5 65.6

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(ii) anhydrous sodium carbonate after the final heating (½ mark)

(iii) water driven off from the salt (1 mark)

(c) Calculate the amount (in moles) of:

(i) anhydrous sodium carbonate (½ mark)

(ii) water (½ mark)

(d) From the ratio moles of water moles of sodium carbonate

determine the value of “x” in the formula Na2CO3 . x H2O (1 mark)

QUESTION 4

A student followed the procedure given in the laboratory manual to investigate the oxidation of ethanol with potassium dichromate.

(a) Account for the underlined phrase in the following step taken during the experiment:

A mixture of 10 drops of ethanol, 15 drops of dilute sulphuric acid and 5 drops

of potassium dichromate was warmed in a hot water bath. (½ mark)

(b) When the mixture was warmed for a few minutes, the potassium dichromate changes its colour from orange to green.

What does the colour change indicate about the reaction? (½ mark)

(c) During the change of colour of potassium dichromate a sharp smell was noticed

coming out of the test tube. What is this sharp smell due to? (½ mark)

(d) Complete the following equation for the reaction given above.

CH3CH2OH (1 mark)

(e) Breathalysers use the oxidation of alcohol by potassium dichromate to detect the presence of alcohol in a person’s breath.

Explain how a breathalyser works. (1½ marks)

Turn Over

+ 2

7 2O Cr

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(f) Write the formula and the name of the oxidation product formed during the

oxidation of methanol. (1 mark)

QUESTION 5

(a) In a reaction between iron and copper sulphate the following instructions were given.

I. Immerse a small ball of steelwool in 100 mL of copper sulphate solution in a beaker.

II. Decant 10 mL of the solution into a test tube and add 5 mL of a solution of sodium hydroxide.

(i) Write down two observations that would be made in I above. (1 mark)

(ii) What observation would be made when sodium hydroxide is added

to the decanted solution in II? (½ mark)

(iii) Write a complete and balanced equation for the reaction in I above. (1 mark)

(b) Zinc reacts with dilute hydrochloric acid according to the equation.

) g ( 2 ) aq ( 2 (aq)

) s

( 2HCl ZnCl H

Zn

(i) Write a balanced ion-electron equation for the reaction shown above. (1½ marks)

(13)

SECTION C

[45 marks] The five questions in this section are all compulsory.

Reminder : For the questions involving calculations, ensure that the working is shown and that the equations used in your answers are balanced.

QUESTION 1

(a) The Periodic Table for the first 20 elements is shown below.

1 1.01

H

2 4.00

He

3 6.94

Li

4 9.01

Be

5 10.8

B

6 12.0

C

7 14.0

N

8 16.0

O

9 19.0

F

10 20.2

Ne

11 23.0

Na

12 24.3

Mg

13 27.0

A

l

14 28.1

Si

15 31.0

P

16 32.1

S

17 35.5

Cl

18 40.0

Ar

19 39.1

K

20 40.1

Ca

Use the information in the Periodic Table to answer the following questions.

(i) Write down the electron configuration for the elements Li, Na and K. (1 mark)

(ii) Comment on the trend in the reactivity of the atoms of Li across to Ne. (1 mark)

(iii) Comment on the nature of the oxides of the elements from Na to S. (1 mark)

(iv) Name the element which has bleaching property and is a good bleaching

agent. (½ mark)

(v) Give the symbol of an element that does not take part in chemical

reactions. (½ mark)

(vi) Give the name of the element that burns with a bright yellow flame and

reacts vigorously with cold water to form an alkaline solution. (½ mark)

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SECTION C (continued)

(b) Study the molecular model structures for carbon dioxide and sulphur dioxide molecules given below.

(i) Describe the shapes of the two molecules, CO2 and SO2. (1 mark)

(ii) Explain why the shapes of the two molecules are not the same. (2 marks)

(iii) Give an appropriate explanation for the following statement:

Sulphur dioxide is a polar molecule. (1 mark)

QUESTION 2

(a) The following table contains data which could be used to decide the most suitable conditions for the production of ammonia by the Haber Process.

DATA TABLE

Temperature °C

Percentage of ammonia in the equilibrium mixture

10 atm

50 atm

100 atm

300 atm

1 000 atm

200 51 74 82 90 98

300 15 39 52 71 93

400 4 15 25 47 80

500 1 6 11 26 57

600 0.5 2 5 14 13

1 atmosphere pressure unit (atm) = 101.3 kPa

The equation for the process is: N2(g) + 3H2(g) 2NH3(g)

(i) Is the synthesis of ammonia exothermic or endothermic?

Explain with reference to the data table above. (1½ marks)

Carbon dioxide, CO2

Sulphur dioxide, SO2

C

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(ii) What happens to the percentage yield of ammonia if the pressure is

increased at a constant temperature? (½ mark)

(iii) At which temperature and pressure shown in the data table is the

greatest percentage of ammonia present in the equilibrium mixture? (½ mark)

(iv) In the industrial process a temperature of 400 – 500°C and a pressure of 200 atmosphere are used. Explain why these conditions are used rather

than the one you gave in (iii) above. (1 mark)

(v) The Haber process uses a surface catalyst. Name the catalyst used

in the process. (½ mark)

(b) The pH of a 0.01 mol L-1 hydrochloric acid solution is found to be

approximately 2, whereas the pH of a 0.01 mol L-1 ethanoic acid solution is found to be approximately 5.

(i) What does a pH scale measure? (1 mark)

(ii) Explain why these acids of the same concentration have different

pH values. (1 mark)

(c) Using the Kinetic Theory of gases explain the following:

(i) The pressure of a gas decreases if its temperature is lowered at a

constant volume. (1 mark)

(ii) The pressure of a gas held at constant volume and temperature will

increase if more gas is added to the container. (1 mark)

(d) Diamond and graphite are allotropes of the same element. Explain why

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QUESTION 3

(a) A student titrated 0.19 mol L-1 of potassium carbonate solution against a solution of hydrochloric acid until the end point was reached. The student carried out three trials and the respective volume of hydrochloric acid needed to reach end point for each trial is shown in the table below.

Volume of HCl used (mL) Trial

1 2 3

Initial burette reading (mL) 1.80 1.75 1.63

Final burette reading (mL) 22.50 22.55 22.23

Volume of potassium carbonate used: 25 mL

Indicator used: Phenolphthalein

(i) Which of the two solutions was the standard solution? (½ mark)

(ii) To be used as a standard solution, a substance must have special

characteristics. List two of these characteristics. (1 mark)

(iii) State an observation the student would have made when the end point

was reached. (½ mark)

(iv) Calculate the average volume of hydrochloric acid used for the three

trials to the correct number of significant figures. (1 mark)

(v) The equation for the reaction between hydrochloric acid and potassium carbonate is shown below.

) g ( 2 )

( 2 (aq) (aq)

) aq ( 3

2CO 2HCl 2KCl H O CO

K _l

Calculate the concentration of hydrochloric acid. (1½ marks)

(vi) Near the end of the titration the student used a wash bottle containing distilled water to wash any material clinging to the inside of the conical flask down into the mixture. Explain with a reason if the added water

would affect the end point of the titration. (1 mark)

(b) During the course of the titration the student pipetted the standard solution into the conical flask after rinsing the flask first with distilled water and then with the standard solution.

(i) Was this a good experimental procedure? (½ mark)

(17)

(c) Haematite, an iron ore contains ferric oxide that is used in the extraction of iron. A 600 g sample of crude haematite contained 224 g of iron.

(i) Calculate the mass of oxygen in the ferric oxide (Fe2O3). (1 mark)

(ii) Determine the percentage of ferric oxide (Fe2O3) in the 600 g sample

of crude haematite. (1 mark)

QUESTION 4

Consider the following reaction sequence to answer the questions that follow.

(a) (i) In the space provided in the Answer Book, name the compounds

A, B, C and D. (2 marks)

(ii) Name the Reagents I and II. (1 mark)

(iii) Name the process that converts Compound D to Compound E. (½ mark)

(iv) What type of reaction does Compound A undergo to be converted to

C2H6? (½ mark)

(v) Name the process that converts Compound B back to Compound A. (½ mark)

(vi) Write the chemical formula of Reagent III that converts Compound B

back to Compound A. (½ mark)

Compound A Compound B

C2H5OH

Compound A

C2H6 ClCH = CHCl

Compound C

C2H5Cl

Compound D

CH2 = CHCl

Reagent

II

Reagent

I

base Cl2

+ H2O/H+

Reagent III

Compound E

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(b) Write a balanced ion-electron equation for each of the following reactions.

(i) Cl – Cl2 (1 mark)

(ii) MnO4 – Mn2+ (1 mark)

(c) In the space provided in the Answer Book, draw the electron dot diagram (Lewis Structure) for a nitrogen trichloride (NCl3) molecule and circle the

lone pair of electrons. (1 mark)

(d) Given that carbon monoxide (CO) burns according to the equation:

kJ 566 H

; CO 2 O

CO

2 ₍_g₎ ₂₍_g₎ ₂₍_g₎

Calculate the enthalpy change when 2.8 g of carbon monoxide was burnt. (1 mark)

QUESTION 5

(a) Aluminium oxide does not react with water but with an acid and with a base.

(i) What term is used to describe an oxide with this property? (½ mark)

(ii) Complete the following equation in the Answer Book.

Al2O3 + ___OH – (½ mark)

(iii) Give the name of the product produced in (ii) above. (½ mark)

(b) The table given below summarises the reaction of a number of pairs of solutions. Five pieces of information are missing and these are labelled (i) to (v).

Reacting solution

Observation Ions present in the solution

A few drops of sodium hydroxide is added followed by excess.

brick red precipitate (i)

(ii) Al3+

pale blue precipitate (iii)

A few drops of acidified silver nitrate.

(iv) Cl–

A few drops of barium chloride followed by dilute hydro-chloric acid.

white precipitate that remains insoluble when hydrochloric acid is added

(v)

Write the appropriate information beside numbers (i) to (v) in the Answer

(19)

(c) Chlorine gas is prepared by the addition of concentrated hydrochloric acid to calcium hypochlorite [Ca(OCl2)2].

The gas is bubbled through a solution of potassium iodide.

(i) Complete the equation showing the production of chlorine gas in the space provided in the Answer Book.

16HCl(aq) + 2KMnO4(s) 2KCl(aq) + 8H2O(l) + + (1 mark)

(ii) State an observation that is made when the gas is bubbled through

potassium iodide solution. (1 mark)

(iii) Name the chemical species present in the solution that causes the

observation in (ii) above. (½ mark)

(iv) Name a compound of chlorine which is used in the paper and pulp

industry. (½ mark)

(v) What is the purpose of using the compound named in (iv) above? (½ mark)

(d) Using the Bronsted-Lowry Theory describe:

(i) an acid

(ii) a base.

(1 mark)

(e) Give the systematic name of the following organic compound.

(½ mark)

H C

O

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SECTION D

[10 marks] There are four questions in this section. Answer only one question.

Reminder : For the questions involving calculations, ensure that the working is shown and that the equations used in your answers are balanced.

QUESTION 1 CONSUMER CHEMISTRY

(a) Polymers are large molecules made up of repeating small units called monomers.

(i) Name the process of forming a polymer from its constituent monomers. (½ mark)

(ii) Give two examples of natural polymers. (1 mark)

(iii) Name the monomer unit for the manufacture of polythene

or polyethylene. (½ mark)

(iv) State the two conditions under which themonomer unit in (iii) above is

converted to polythene or polyethylene. (1 mark)

(b) Match the terms in the list given below with the descriptions (i) to (iv) by writing the terms beside the correct numbers (i) to (iv) in the Answer Book.

sulphur PVC sodium hydroxide

oxygen glucose sodium hypochlorite

dacron glycerol

(i) a condensation polymer

(ii) an element that gives strength, hardness and elasticity to rubber

(iii) a by-product of soap manufacture

(iv) a common household bleach (2 marks)

(c) When soap is used in hardwater, a precipitate called “scum” is formed.

(i) Write the formula of the two ions that cause hardness in water. (1 mark)

(ii) What advantage does a detergent have over soap when used in

hard water? (½ mark)

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(d) Solvent cleaners are usually organic compounds that are used for removing oily and greasy stains on fabrics.

(i) Name two common organic solvents. (1 mark)

(ii) Most organic solvent are highly flammable. Suggest two safety

precautions when handling these chemicals. (1 mark)

(e) Addition polymers are made using condensation reactions.

(i) Name a secondary product of condensation polymerisation. (½ mark)

(ii) Teflon is an addition polymer made from tetrafluoroethene.

Draw the structure of tetrafluoroethene. (½ mark)

QUESTION 2 CHEMISTRY OF FOOD

(a) Butter and margarine are common spreads used in most households in Fiji. Margarine is a product formed from polyunsaturated vegetable oil.

(i) Name the process that converts vegetable oil into margarine. (½ mark)

(ii) State two conditions that are required for the conversion of vegetable oils

into margarine. (1 mark)

(iii) What does the term “polyunsaturated” mean? (½ mark)

(iv) State why the onset of rancidity is faster in butter than in margarine. (½ mark)

(v) Explain how you would test for unsaturation in vegetable oil. (1 mark)

(b) Match the terms in the list given below with the description (i) to (iv) by writing the terms beside the correct numbers (i) to (iv) in the Answer Book.

starch refining stabiliser

glycogen deodorizing emulsifier

condensation hydrolysis

(i) the process of removing impurities from lipids by adding sodium hydroxide

(ii) a polysaccharide used in ice-cream that thickens the aqueous phase to prevent coalescing of fat globule

(iii) storage form of glucose in animals

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SECTION D (continued)

(c) The cyclic structure of glucose is drawn below.

(i) Write down the molecular formula for glucose based on the structure

drawn above. (½ mark)

(ii) Explain why the cyclic structure of glucose does not form a brick red

precipitate with Benedict Solution. (1 mark)

(iii) Copy and complete the equation below in the Answer Book showing the reaction between glucose and Benedict’s solution.

+ Cu₍2_aq₎ + 4OH₍_aq₎ + (1 mark)

(d) Given below are laboratory instructions for carrying out a test for protein. These instructions contain errors.

To show the test for protein, place 5 mL of protein-food solution in a test tube.

Add a few drops of iodine solution and warm the solution to about 60°C. The

formation of violet (purple) coloured solution indicates the presence of protein.

(i) Identify the errors and state the correct procedures. (1 mark)

(ii) Write the structural formula of the two functional groups present in

amino acid, a monomer for protein. (1 mark)

C O

H

C HO

HO C

H

C

H

O

H

C

OH

C H

(23)

QUESTION 3 CHEMISTRY IN THE ENVIRONMENT

Study the diagram given below which shows the solubility of three mineral nutrients as a function of pH. The changing width of each band indicates the relative solubility of the minerals between pH = 4 and pH = 10.

(a) Name the mineral which is most soluble in the:

(i) neutral pH range. (½ mark)

(ii) alkaline pH range. (½ mark)

ion-exchange kidney lime

leaching bone urea

humus manure

(i) site where most of the lead accumulates in our body

(ii) decomposed plant material

(iii) ions needed by plant roots are released into the soil water and carried to deeper levels in the soil

(iv) raises the pH of soil thus making the soil more suitable for plant

growth (2 marks)

(c) The pH of soil samples from two areas were determined. Sample A had a pH of 5 while sample B had a pH of 6.

(i) Which sample is more acidic? (½ mark)

(ii) Explain why the sample you have chosen in (i) is more acidic. (½ mark)

(24)

SECTION D (continued)

(iii) Alkaline soils have a pH greater than 7. Name one mineral or element

that is deficient in alkaline soils. (½ mark)

(d) Discuss the effects of the following activities on our environment:

(i) the use of aerosol sprays and freon in refrigerators and air conditioners (1 mark)

(ii) the spilling of crude oil in the sea from oil wells (1 mark)

(iii) the dumping of old car batteries in residential areas (1 mark)

(e) The last stage in many water treatment plants involves fluoridation where fluoride is added to the water.

(i) Name one chemical compound that is added to the water as a source of

fluoride. (½ mark)

(ii) Give one advantage of drinking fluoridated water. (1 mark)

(iii) Studies have shown that high levels of fluoride in drinking water is detrimental to human health. In what way is too much fluoride harmful

to human health? (1 mark)

QUESTION 4 CHEMISTRY OF COPPER AND ITS COMPOUNDS

(a) Copper is often purified by electrodeposition.

(i) Write the equation for the reaction occurring at the anode in such a

purification process. (1 mark)

(ii) At which of the electrodes is blister copper used. (½ mark)

(iii) Give one agricultural use of compounds of copper. (½ mark)

chalcopyrite anaemia froth flotation

magnetire hypertension smelting

silicon dioxide nitrogen dioxide

(25)

(ii) source of copper

(iii) symptom of lack of copper in our diet

(iv) a slurry of finely ground ore, water and collectors (2 marks)

(c) Copper (II) tetrammine sulphate is a complex salt.

(i) Write the formula of the complex ion present in the salt. (½ mark)

(ii) Describe briefly how you would prepare the complex salt

copper (II) tetrammine sulphate. (2 marks)

(d) Use the information below to answer the questions that follow.

2.54 g of copper metal was completely dissolved in 30 mL of concentrated nitric acid solution. When excess sodium hydroxide solution was added to the resulting solution a light blue precipitate was formed. The light blue precipitate was heated and a black solid was formed. The black solid was then filtered, washed with acetone, dried and weighed. Its weight was found to be 3.08 g.

(i) Name the light blue precipitate formed in the reaction. (½ mark)

(ii) Write an equation to show how the black solid is formed when the

light blue precipitate is heated. (1 mark)

(iii) What mass of oxygen was present in 3.08 g of the black solid? (½ mark)

(iv) From the experimental data determine the empirical formula of the

black solid. (1½ marks)