Structured questions

1 Consider the following plastics which can be classified as thermoplastics and thermosetting

plastics:

polythene, perspex, urea-methanal, nylon

a) What does ‘thermosetting plastics’ mean?

b) Classify the above plastics into thermoplastics and thermosetting plastics.

c) Explain which of the above plastics can be used to make the following items:

i) handle of a cooking pot;

ii) glass substitute for advertising displays.

d) Polythene is made from ethene.

i) Name the type of polymerization involved in the production of polythene from

ethene.

ii) Write a chemical equation for this polymerization.

e) Nowadays, plastics are widely used as substitutes for metals. State TWO advantages of

using plastics instead of metals.

f) Suggest how

i) the public,

ii) the government and

iii) the manufacturers of plastic products

can help reduce pollution problems associated with the disposal of plastic waste.

(15 marks)

2 A plastic bag is produced by the following procedures:

a) What is Process 1?

b) The heavy oil contains a mixture of saturated hydrocarbons, e.g. C9H20 and C12H26.

i) What is the meaning of ‘saturated hydrocarbons’?

ii) Name Process 2 and Process 3.

iii) Write a chemical equation for the production of ethene from C12H26.

c) What will be observed if ethene is bubbled into

i) acidified potassium dichromate solution?

ii) bromine dissolved in 1,1,1-trichloroethane?

d) Ethene can undergo polymerization to give polythene.

i) What characteristic in the structure of ethene enables it to act as a monomer?

ii) Draw the repeating unit of polythene.

iii) Is polythene a thermoplastic or a thermosetting plastic? Explain your answer in

terms of its structure.

iv) State ONE advantage of using polythene in the manufacture of plastic bags.

e) Apart from polythene, polypropene can also be used to make plastic bags and its

monomer is propene.

i) Draw the electron diagram of propene, showing the outermost shell electrons only.

ii) Write a chemical equation for the polymerization of propene.

f) Landfilling and incineration are two possible ways to treat polythene waste.

i) Explain how landfilling and incineration of polythene waste cause pollution

problems.

ii) Suggest another way to treat polythene waste.

(18 marks)

3 a) Plastic X can be used to manufacture medicine bottles. It has the followingstructure:

i) (1) Draw the structure of the monomer of plastic X.

(2) Name the monomer.

ii) Name the TWO main processes involved in the production of bottles from the

monomer of plastic X.

iii) What will be observed if the monomer is added to bromine dissolved in an organic

solvent? Explain your answer.

iv) What will be observed if plastic X is added to bromine dissolved in an organic

solvent?

v) State ONE property of plastic X which makes it suitable for making medicine

bottles.

vi) A water bottle is made of plastic X. Can this bottle be remoulded into other shapes?

Explain your answer.

vii) Recycle and reuse are two possible solutions for the disposal problem of plastic

bottles.

(1) What preliminary treatment of bottles made of plastic X is required before

recycling?

(2) Before reusing bottles, bottles would need to be sterilized first. Glass bottles are

sterilized using superheated steam. Why might this method be unsuitable for

some types of plastic bottles?

b) The repeating unit of a polyester is shown below:

i) Draw the structure of the dioic acid which could be used in the preparation of this

polyester.

ii) Give ONE reason why this polyester is biodegradable.

(15 marks)

4 Polystyrene is a polymer which is widely used in our daily lives. Its structure isshown below:

a) What does ‘polymer’ mean?

b) Draw the structure of the monomer of polystyrene.

c) Name the type of polymerization involved in the production of polystyrene.

d) Suggest why polystyrene does NOT have a constant relative molecular mass.

e) Expanded polystyrene can be used to make foam cups and lunch boxes.

i) Suggest ONE reason why expanded polystyrene is used to make foam cups and

lunch boxes.

ii) Suggest another common use of expanded polystyrene. State ONE property of

expanded polystyrene associated with this usage.

f) Polystyrene can be prepared from styrene with the following set-up:

i) Suggest the function of the cold finger in the experiment.

ii) What are the functions of kerosene in the experiment?

iii) State ONE potential hazard of the experiment.

iv) Draw a labelled diagram of an alternative set-up for the preparation of polystyrene.

v) After the reaction, the reaction mixture is poured into a beaker of methanol.

(1) What is the function of the methanol?

(2) What will be observed when the reaction mixture is poured into methanol?

(15 marks)

5 PVC, which is known as polyvinyl chloride, is often used in the manufacture ofplastic bags

and drainage pipes.

a) What is the monomer of PVC?

b) Write a chemical equation for the formation of PVC from its monomer.

c) PVC is formed by addition polymerization. What is meant by the term ‘addition

polymerization’?

d) Explain with TWO reasons why PVC is a better material in the manufactureof drainage

pipes than iron.

e) Suggest an experiment to show that a piece of PVC is a thermoplastic.

f) Incineration is one of the ways to dispose of PVC waste. However, it maylead to

pollution problems.

i) Suggest TWO air pollutants that will be produced during theincineration of PVC

waste.

ii) State ONE harmful effect of each pollutant suggested in (i).

iii) Suggest ONE way to reduce the emission of each pollutant suggestedin (i).

iv) Suggest another way to dispose of PVC waste. Give ONE advantage ofthis way.

(15 marks)

6 Perspex can be used as a substitute for glass. Its structure is shown below:

a) Draw the monomer of perspex.

b) Write a chemical equation for the formation of perspex from its monomer.

c) Perspex can be used instead of glass to make camera lenses.

i) Why can perspex be used as a substitute for glass?

ii) State ONE advantage and ONE disadvantage of using perspex instead of glass to

make camera lenses.

d) i) Determine the relative molecular mass of perspex if the number of repeating units in

each molecule of perspex is 2 500.

ii) What is the percentage by mass of hydrogen in perspex?

e) Perspex can be broken down into its monomer using the set-up shown below.

i) What is the function of the ice water?

ii) State ONE potential hazard of the above experiment.

iii) What will be observed if liquid X is added to acidified potassium permanganate

solution? Explain your answer with the help of a chemical equation.

f) Suggest TWO reasons for the recycling of perspex waste.

(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0)

(17 marks)

7 In laboratory, cracking of an alkane C11H24 gives a saturated hydrocarbon and anunsaturated

hydrocarbon with three carbon atoms in its molecule.

a) i) Write a chemical equation for the cracking of C11H24.

ii) Suggest a catalyst for the cracking of C11H24.

iii) Draw a labelled diagram to show how the cracking of C11H24 can becarried out in

the laboratory, including the collection of the gaseousproduct.

iv) Apart from bromine, suggest ONE reagent which can be used to showthe presence

of an unsaturated hydrocarbon in the product mixture.State the expected

observation.

b) The unsaturated hydrocarbon obtained in the above experiment can be used to make a

polymer.

i) Name the polymer produced.

ii) Draw the structure of the polymer.

iii) Can the polymer produced decolourize bromine dissolved in 1,1,1-trichloroethane?

Explain briefly.

c) Explain whether the polymer in (b) can be used to make the following items.

If your answer is ‘no’, suggest another polymer which is more suitable for the production

of that item.

i) Electric socket

ii) Aircraft window

iii) Yogurt container

(18 marks)

8 a) For each task listed below, decide which of the two plastics given is the bestfor

Task Plastic

i) To make drainage pipes Urea-methanal / polyvinyl chloride

ii) To make fishing lines Polythene / nylon

iii) To make electric plugs and sockets Polystyrene / urea-methanal

iv) To make packaging materials Perspex / poltthene

v) To make safety spectacles Nylon / perspex

b) State the processes for making safety spectacles from the monomer of plastic chosen in

(a)(v).

c) Polythene waste can be recycled or used as an energy source. State ONE advantage

and ONE disadvantage of

i) recycling polythene waste; and

ii) using polythene waste as an energy source.

d) Name ONE plastic which CANNOT be recycled by melting and remoulding.

(18 marks)

9 Part of the structure of nylon is shown below:

where are two different saturated hydrocarbon chains.

Nylon is formed from condensation polymerization of hexanedioyl dichloride and

hexane-1,6-diamine. Hydrogen chloride is also evolved in the reaction.

a) Why is nylon considered as a condensation polymer?

b) According to the structure of nylon above, draw its monomers.

c) Write a chemical equation for the formation of nylon from its monomers.

d) Suggest ONE disadvantage of using nylon fibre for making clothes.

e) Nylon can be prepared in the laboratory with the following procedure.

1 Pour 10 cm3 of hexanedioyl dichloride dissolved in 1,1,1-trichloroethane into a

beaker.

2 Slowly add 10 cm3 of hexane-1,6-diamine solution (in sodium hydroxide solution)

to the beaker.

3 A white film of nylon is formed at the interface between the two immiscible

solutions.

i) How can we show that hydrogen chloride is evolved in the polymerization?

ii) Suggest ONE function of sodium hydroxide solution.

iii) Why does the polymerization take place at the junction of the two solutions?

iv) How can nylon be obtained from the interface of the solutions?

v) Suggest where the experiment should be performed. Explain your answer.

f) “Nylon is non-biodegradable.”

What does this statement mean?

(13 marks)

10 A synthetic polymer can be produced from the following two monomers:

where x and y represent different lengths of carbon chains.

a) What is the name of this polymerization process?

b) By means of structural formulae, write a chemical equation for the process.

c) Describe briefly how a thread of this polymer can be made in the laboratory.

d) Give ONE physical property of this synthetic polymer and give ONE of its use which is

based on this property.

e) Why does the disposal of nylon waste cause pollution problems?

f) Landfilling and incineration are two common methods for treating plastic waste. For each

of these two methods, state ONE advantage and ONE disadvantage.

(11 marks)

11 a) Two organic compounds are shown below.

Compounds A and B are monomers which react together to form a polymer.

i) What are monomers?

ii) Name the type of polymerization involved in the manufacture of the polymer.

iii) State a common characteristic of compounds A and B which enables them to

undergo the type of polymerization suggested in (ii).

iv) Draw the repeating unit of the polymer.

v) Apart from the polymer, small molecules are also produced during the reaction.

Draw an electron diagram of the small molecule produced, showing the outermost

shell electrons only.

vi) Suggest ONE use of the polymer.

b) Plastic X can be used to make a wide range of articles. It has the following structure:

i) (1) Draw the structure of the monomer of plastic X.

(2) Name the monomer.

ii) Products made of plastic X may vary greatly in rigidity.

(1) Give ONE flexible product made of plastic X.

(2) Give ONE rigid product made of plastic X.

(3) Explain whether plastic X is suitable for making the handle of a frying pan or

not.

iii) In many countries, plastic waste is collected and sorted. Some of this is incinerated

to provide heat for power stations.

Why should plastic X be removed from any waste that is to be incinerated?

(12 marks)

12 Urea-methanal is a plastic which can be made using coal as a feedstock. Theflow diagram

below shows the steps involved in the production process.

a) In Step 2, methanol is manufactured from carbon monoxide and hydrogenaccording to

the following equation:

CO(g) + 2H2(g) → CH3OH(l) (H is negative)

Under suitable conditions, 50.0 dm3 of carbon monoxide and 50.0 dm3 ofhydrogen are

allowed to react. The volumes of both gases are measured at room temperature and

pressure.

i) What is meant by ‘H is negative’?

ii) Calculate the theoretical mass of methanol obtained.

b) Name the type of reaction taking place in Step 3.

c) Suggest how Step 4 can be carried out in the laboratory.

d) The structures of urea and methanal are shown below:

Draw the repeating unit of urea-methanal.

e) Urea-methanal does NOT soften on heating. What is the name given to this type of

plastic?

f) i) Urea-methanal is formed by condensation polymerization. What is meant by the

term ‘condensation polymerization’?

ii) State a common characteristic of those monomers which can form condensation

polymers.

g) Name a moulding method for urea-methanal.

h) The following diagrams show three plastic items. One of them is made of urea-methanal.

i) Which of the above items is made of urea-methanal? Explain your answer.

ii) (1) Name ONE plastic which is suitable for making stockings.

(2) What is the type of polymerization involved in making the plastic named in

(1)?

(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0; molar volume of any gas at room

temperature and pressure = 24.0 dm3 mol-1)

(17 marks)

13 The structures of five compounds, I, II, III, IV and V are shown below:

where represent different saturated hydrocarbon chains.

Some of the compounds above can give polymers under suitable conditions.

a) Explain the meaning of ‘polymer’?

b) i) Which compound can be used to make an addition polymer?

ii) Draw the repeating unit of the polymer formed in (i).

iii) Would you expect the polymer formed to be a thermoplastic or a thermosetting

plastic? Explain your answer.

c) Which compound can be used to make a condensation polymer?

d) i) Which TWO compounds would react together to form an ester?

ii) Draw the structure of the ester formed from the compounds suggested in (i).

iii) The ester formed can be hydrolysed with dilute sodium hydroxide solution.

(1) Draw a labelled diagram of the laboratory set-up for the hydrolysis.

(2) Draw structures of the products formed.

e) Suggest ONE chemical test to distinguish between compounds II and V. State the

expected observations.

(15 marks)

14 a) Each of the following tasks can be accomplished by using either material A or B.

TaskMaterials

A B

i) To make shopping bags Polythene Paper

ii) To make windows Perspex Glass

iii) To make drainage pipes PVC Iron

iv) To make storage boxes PVC Wood

v) To make clothes Nylon Cotton

vi) To make the case of a rice cooker Urea-methanal Steel

In each case, state ONE advantage of

(1) using A over B to accomplish the task.

(2) using B over A to accomplish the task.

(You are NOT required to consider the prices of the materials.)

b) Explain briefly how a straight PVC pipe can be bent to fit the curvature in a drainage

system.

c) Explain which material in column A is different from the others in terms of structure.

(15 marks)

15 Plastics are very useful materials. Many objects previously made with metals are now made of

plastics.

a) For each of the following objects, suggest ONE advantage of using plastics over using

metals in making the object.

i) a water pipe

ii) a cycle frame

iii) a lamp post

iv) a helmet for a soldier

b) Pyrolysis can be used to treat plastic waste. During pyrolysis, plastic waste is

decomposed at high temperature in the absence of air. A mixture of products, including

methane and ethene, is formed.

i) Explain why it is necessary to carry out the pyrolysis in the absence of air.

ii) State a method for separating methane from other pyrolysed products.

iii) Suggest a chemical test to distinguish between methane and ethene.

iv) State ONE use of methane and ONE use of ethene.

v) State ONE advantage and ONE disadvantage of treating plastic waste by pyrolysis.

vi) Plastic waste can also be recycled by melting and remoulding. State ONE difficulty

of employing this method to treat plastic waste.

(13 marks)

PlasticProperties

Appearance Behaviour on heating Flexibility Price per kg ($)

A transparent softens readily stiff 40

B opaque burns readily stiff 10

C opaque Does not soften stiff 350

D opaque burns readily flexible 12

a) Which of the above plastics is/are thermosetting plastic(s)? Explain your answer.

b) Which of the above plastics is the most suitable for making

i) packaging materials;

ii) an ashtray;

iii) a water bucket?

Explain your choice in each case.

c) Disposal of plastic waste can cause pollution problems. The pollution problems can be

reduced by the recycling of plastic waste.

i) Besides recycling, suggest THREE other methods for treating plastic waste.

ii) State TWO advantages of recycling plastic waste.

iii) State TWO disadvantages of recycling plastic waste.

iv) Suggest how you can help reduce pollution problems associated with the disposal of

plastic waste.

(16 marks)

17 a) Teflon (PTFE) is a polymer which is commonly used in making the material coated on

non-stick frying pans. Part of the structure of Teflon is shown below:

i) Draw an electron diagram of the monomer of teflon, showing electrons in the

outermost shells only.

ii) Upon analysis of a teflon sample, 11.6 g of the sample is found to contain 8.74 g of

fluorine. Calculate the percentage purity of the teflon sample.

iii) Teflon is a thermoplastic. Suggest ONE property of teflon which is different from

other common thermoplastics.

b) Polystyrene can be prepared in the laboratory by heating a mixture of styrene and

kerosene under reflux. Polystyrene has the following structure:

i) Draw the structure of the monomer of polystyrene.

ii) Write a chemical equation for the polymerization of styrene.

iii) Draw a labelled diagram of the laboratory set-up used for heating the mixture under

reflux.

iv) Suggest, with explanation, a safety precaution that should be taken in the

preparation.

v) Suggest ONE use of polystyrene.

vi) Disposable cups for hot drinks are commonly made of expanded polystyrene.

Suggest ONE reason why polystyrene should be expanded before it is used to make

the disposable cups.

vii) Suggest TWO air pollutants that are given off when polystyrene undergoes

incineration.

viii) How could the amount of the air pollutants in (vii) be minimized? Explain briefly.

(Relative atomic masses: C = 12.0, F = 19.0)

(17 marks)

18 Consider the following organic compounds.

where represents a saturated hydrocarbon chain.a) Which of the compounds, D, E, F or G, can decolourize acidified potassium

permanganate solution? Name the type(s) of reactions involved.

b) State all the functional groups present in compound H.

c) i) Which compound(s) can undergo addition polymerization?

ii) Draw the repeating unit(s) of the polymer(s) formed from the compound(s)

mentioned in (i).

iii) State ONE use of each polymer mentioned in (ii).

d) Two pairs of the above compounds can undergo condensation polymerization.

i) What is condensation polymerization?

ii) Which TWO pairs of compounds can undergo condensation polymerization?

iii) What common characteristic in the structures of the compounds mentioned in (ii)

enable them to act as monomers?

iv) Draw the repeating units of the polymers formed from the pairs of compounds.

v) State ONE use of each polymer mentioned in (iv).

(20 marks)

19 a) Plastics are widely used nowadays. There are two types of plastics.

Their structures are shown below:

i) Which of the above structures represents a thermosetting plastic? Explain your

answer.

ii) Give ONE example for each type of the plastics above.

iii) Which of the above plastics can be remoulded? Explain your answer.

iv) Nowadays, plastics rather than wood are used to make chairs. Suggest TWO

advantages of plastic chairs over wooden chairs.

b) Terylene is a polyester fibre which is used in the manufacture of shirts. It is synthesized

from ethane-1,2-diol (HOCH2CH2OH) and benzene-1,4-dicarboxylic acid

(HOOCC6H4COOH).

i) Ethane-1,2-diol can be produced from ethene in the laboratory. State the chemical

other than ethene required for the production and write a chemical equation for the

reaction involved.

ii) Name the type of polymerization involved in the synthesis of terylene.

iii) Draw the repeating unit of terylene.

c) Recycling, landfilling, incineration and pyrolysis are four common methods for treating

plastic waste. For each of these methods, state ONE advantage.

(16 marks)

20 The following table shows some properties of four detergents.

Detergent pH value of the

detergent

Is it

biodegradable?

Does it form scum

with hard water?

W 5 Yes No

X 6 Yes No

Y 7 No No

Z 8 Yes Yes

a) Which of the above detergents is / are soapy detergent(s)? Explain your choice.

b) i) Name the ions which cause the hardness of water.

ii) (1) Name a substance which can reduce the hardness of water.

(2) Explain, with the help of an ionic equation, why the substance mentioned in (1)

can reduce the hardness of water.

c) Which of the above detergents CANNOT be used in a strongly acidic medium? Explain

your choice.

d) In general, biodegradable detergents cause fewer pollution problems than

non-biodegradable detergents.

i) What does ‘biodegradable detergents’ mean?

ii) Suggest a structural characteristic of a detergent that makes it biodegradable.

iii) Suggest ONE pollution problem associated with non-biodegradable detergents.

iv) Biodegradable detergents can also pose hazards to the environment. Explain briefly.

e) Detergent is sprayed over petroleum patches on the sea in case of a petroleum leakage.

Explain briefly the action of detergent in this process.

(17 marks)

21 There are two types of detergents: soapy detergents and soapless detergents.

a) Describe briefly how a soapy detergent can be prepared from vegetable oil in a school

laboratory.

b) State TWO materials required in the manufacture of soapless detergents.

c) Describe how you can distinguish between a soapy detergent and a soapless detergent.

d) If the general formula of a soapy detergent is CnH2n+1COO-Na+ and its formula mass is

320. What is the formula of the soapy detergent?

e) Compare soapy and soapless detergents in terms of their environmental impacts.

f) Explain why phosphate additives in detergents can cause the death of aquatic life.

(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0, Na = 23.0)

(14 marks)

22 The structure of detergent X is shown below:

CH3(CH2)16COO-Na+

a) i) Which part of the detergent is hydrophilic?

ii) Which part of the detergent is hydrophobic?

b) Explain briefly how detergent X can remove the oily dirt on a shirt in water.

c) i) What is ‘Hard water’?

ii) State whether detergent X can function well in hard water. Explain your answer with

the aid of an ionic equation.

d) i) Explain why detergent X CANNOT function well in acidic solutions.

ii) Suggest ONE substance which can reduce both the hardness and acidity of water.

e) An oil tanker was wrecked and spilt a lot of crude oil into the sea. State whether detergent

X is suitable for treating the oil spill. Explain your answer.

(14 marks)

23 The structure of detergent X is shown below:

a) i) Which part of the detergent is hydrophilic?

ii) Which part of the detergent is hydrophobic?

b) Detergent X, when shaken with a mixture of water and paraffin oil, gives an emulsion.

With reference to its structure, explain this phenomenon.

c) Explain how detergent X can clean crude oil spills in the sea.

d) i) Is detergent X biodegradable?

ii) Suggest, with explanation, an environmental consequence associated with the

discharge of waste water containing detergent X into rivers and lakes.

e) A sample of natural hard water contains the following ions:

● Calcium

● Chloride

● Hydrogencarbonate

● Magnesium

● Sodium

● Sulphate

i) Which TWO ions above make the water hard?

ii) Explain whether detergent X can function well in hard water.

(13 marks)

24 Soapless detergents and soapy detergents are common cleaning agents.

a) Suggest TWO substances that are used in the production of soapy detergents.

b) i) Which type of the above detergents may irritate skin? Explain your answer.

ii) Suggest ONE safety measure when handling the detergent mentioned in (i).

c) The structures of three detergents are shown below:

i) Which of the above detergents is / are biodegradable?

ii) Which detergent(s) CANNOT be used in an acidic medium?

iii) What will be observed when the three detergents are added to dilute calcium nitrate

solution separately?

d) Draw a diagram to show how the detergent particles make an oil droplet suspend in

water.

e) A mixture of oil and water is shown below.

i) What will be observed when the mixture is shaken and then allowed to stand for a

long time?

ii) What will be observed when the mixture is shaken with concentrated sodium

hydroxide solution? Explain the observation.

(19 marks)

25 The structure of an animal fat is shown below:

a) Animal fat is one of the raw materials in the production of soapy detergent.

i) Name another raw material that is needed in the production of soapy detergent from

an animal fat.

ii) Name the type of reaction that takes place in the production of soapy detergent.

Briefly describe how you would prepare soap from the animal fat above in the

laboratory.

iii) Write a chemical equation for the reaction involved in the preparation.

b) The relative molecular mass of the animal fat shown above is 806. What is the value of

n?

c) i) Explain why soapy detergents CANNOT be used in acidic solutions.

ii) Explain, with the help of an ionic equation, why sodium carbonate can help soapy

detergents to function well in acidic solutions.

d) How do soapy detergents cause environmental problems?

(15 marks)

26 Soap can be formed when sodium hydroxide reacts with an animal fat with thefollowing

structure:

where n is a positive integer.

In an experiment, 44.5 g of the animal fat were heated under reflux with 100.0 cm3 of 2.50 M

sodium hydroxide solution until the fat was completely reacted.

The resulting solution was allowed to cool to room temperature.

a) Write a chemical equation for the formation of soap from this fat.

b) Name the type of reaction involved.

c) 10.0 cm3 of the resulting solution were withdrawn and titrated against 0.650M

hydrochloric acid. 15.4 cm3 of the acid were required to reach the end point.

Calculate the value of n in the structural formula of the animal fat.

d) Concentrated sodium chloride solution was added to the resulting solution after reflux.

What is the purpose of adding concentrated sodium chloride solution?

e) The structure of a certain soapless detergent is shown below:

i) What other raw materials, apart from sodium hydroxide, are required in the

manufacture of this soapless detergent?

ii) Give ONE advantage and ONE disadvantage of using this soapless detergent for

domestic cleaning compared with using a soapy detergent.

(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0)

(13 marks)

27 A new brand of glass cleaner has been produced recently. The label displayed on its bottle is

shown below:

Super Glass Cleaner

Major ingredient:

Ammonia

Cautions:

Keep away from children.

Wear plastic gloves when handling it.

Do not...........

a) What will be observed when a few drops of methyl orange solution are added into a few

cm3 of the glass cleaner?

b) Why should we wear plastic gloves when handling the glass cleaner?

c) On the label, some words are missing in the third warning statement.

Complete the third warning statement, beginning with ‘Do not’. Explain your answer.

d) Explain how the glass cleaner can remove oil on glass.

e) Oven cleaner contains concentrated sodium hydroxide solution which is used to remove

grease in oven. Explain why oven cleaner CANNOT be used to clean windows.

f) Give ONE advantage and ONE disadvantage of using a soapy detergent for domestic

cleaning compared with using a soapless detergent.

g) i) Explain why plastic is suitable for making the bottle of the glass cleaner.

(13 marks)

28 A student heated an ester, CH3(CH2)17COOC2H5, with concentrated sodium hydroxide solution

under reflux. Then he added concentrated sodium chloride solution to the reaction mixture and

a layer of creamy substance was formed on the surface of the solution.

a) i) Name the type of reaction took place. Write a chemical equation for the reaction

involved.

ii) Draw a labelled diagram of the apparatus used for heating the ester with

concentrated sodium hydroxide solution under reflux.

iii) What is the creamy substance?

iv) What is the purpose of adding concentrated sodium chloride solution?

v) State ONE use of the creamy substance.

b) Draw a labelled diagram of the apparatus used for separating the creamy substance from

the reaction mixture.

c) What would be observed if a small amount of the creamy substance is dissolved in water

and then added to sea water? Explain your answer with the help of an ionic equation.

d) The creamy substance can pose hazards to the environment. Explain how it affects the

environment.

(15 marks)

29 a) A soapless detergent can be produced by the following procedures:

where represents a saturated hydrocarbon chain.

i) (1) What should Process A be?

(2) State the underlying principle of Process A .

ii) (1) Suggest what substance B should be.

(2) Write a chemical equation for the reaction between −CH2SO3H and

substance B.

iii) What will be observed when the soapless detergent is added to a mixture of water

and oil?

iv) The hydrocarbon chain of the soapless detergent can be straight or branched. How

do they differ in terms of their impacts on the environment?

v) Suggest ONE precaution when handling soapless detergents. Explain your answer.

vi) Phosphate additives in commercial soapless detergents can increase the effectiveness

of the detergents. However, the additives may cause serious pollution problems.

Explain briefly how the additives may cause serious pollution problems.

b) Some cleaning agents contain concentrated sodium hydroxide solution.

i) How can concentrated sodium hydroxide solution remove greasy dirt?

ii) Suggest ONE hazard warning label that should be displayed on a bottle of a cleaning

agent containing concentrated sodium hydroxide solution.

(14 marks)

30 These information is taken from two different brands of spring water.

a) The labels show the names of ions contained in the spring waters. Describe how the ions

got into the spring waters.

b) Both spring waters are hard. Name TWO ions which make them hard.

c) “AA spring water is about twice as hard as BB spring water.”

Describe how you could use soap solution to show that the above statement is correct.

You should state how the experiment is made fair.

d) Hard water can form deposits called scale inside water pipes.

i) Explain why the scale may cause problems in water pipes.

ii) Explain why the scale may be beneficial to lead water pipes.

e) Explain why washing soda, a form of sodium carbonate, can help reduce the hardness of

water.

f) Sodium ions in hard water can be identified using the flame test.

i) Briefly describe the procedure for conducting flame test.

ii) State the colour of flame produced by sodium.

(14 marks)

31 Consider six compounds A, B, C, D, E and F below:

where andand represent different saturated hydrocarbon chains.

a) i) Which of the compounds above can turn moist blue litmus paper red?

ii) State the observation(s) when magnesium ribbons are added to the aqueous

solution(s) of the compound(s) mentioned in (i).

b) Which of the compounds can undergo addition polymerization? Draw the repeating

unit(s) of the polymer(s).

c) Which two compounds can react to form a condensation polymer? Write a chemical

equation for the reaction involved.

d) i) Which two compounds can react in 1 : 1 ratio to give an ester when heated under

reflux? Draw the structure of the ester.

ii) Draw a labelled diagram of the set-up used for the production of ester from the

compounds mentioned in (i).

e) i) Which of the above compounds can react with concentrated sodium hydroxide

solution to give soapy detergents?

ii) Write chemical equations for the reactions involved in (i).

iii) State the structural feature of the saturated hydrocarbon chains of the compounds

mentioned in (i) should possess so that good soapy detergents can be produced.

iv) State the difference in cleaning effectiveness between soapy detergents and soapless

detergents in

(1) hard water;

(2) acidic solutions.

(21 marks)

32 Consider the following flow diagram:

a) Name Processes A, B, C and D.

b) What is reagent 1?

c) Suggest a chemical test for alkanoic acid Y and write an ionic equation for the reaction

involved.

d) i) Reagent 2 is a sodium compound. When it is added to alkanoic acid Y, it dissolves to

give a colourless solution and no other change is observed. What might reagent 2

be?

ii) Name the type of reaction involved in the conversion of alkanoic acid Y to

RCOO-Na+.

e) When R is a saturated hydrocarbon chain containing 12 to 20 carbon atoms, RCOO-Na+

can act as a soap.

i) Explain why RCOO-Na+ a+ can suspend oil droplets in water with reference to its

structure.

ii) The formula mass of RCOO-Na+ (CnH2n+1COO-Na+) is 264. What is the number of

carbon atoms in each particle?

iii) Suggest ONE advantage of using the method shown in the flow diagram to produce

a soap.

(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0, Na = 23.0)

(17 marks)

33 There are two types of plastics: thermoplastics and thermosetting plastics.

Discuss how they are different in terms of their structures, thermal properties and uses.

(You are required to give a paragraph-length answer. In this question, 6 marks will be awarded

for chemical knowledge and 3 marks for effective communication.)

(9 marks)

34 Plastics bring us convenience. However, disposal of plastic waste causes negative impacts to

the environment. Describe how the disposal of plastic waste pollutes our environment. Suggest

various ways to reduce the problems caused by the disposal of plastic waste.

(You are required to give a paragraph-length answer. In this question, 6 marks will be awarded

for chemical knowledge and 3 marks for effective communication.)

(9 marks)

35 Recycling and pyrolysis are two common ways of treating plastic waste. Briefly discuss the

two methods.

(You are required to give a paragraph-length answer. In this question, 6 marks will be awarded

for chemical knowledge and 3 marks for effective communication.)

(9 marks)

36 Describe how you can prepare a soap from vegetable oil in the school laboratory. Explain why

soap can remove grease from clothes in water with reference to its structure.

(You are required to give a paragraph-length answer. In this question, 6 marks will be awarded

for chemical knowledge and 3 marks for effective communication.)

(9 marks)

37 Both soapy and soapless detergents can remove oily dirt. Compare the two types of detergents

with respect to the raw materials used in their production; their cleaning abilities in soft water

and hard water; and their impacts on the environment.

(You are required give a paragraph-length answer. In this question, 6 marks will be awarded

for chemical knowledge and 3 marks for effective communication.)

(9 marks)