WORKSHEET/QUESTIONS WITH SOLUTIONS

Q1 The table below gives some properties of elements of group I (J98/p2/A4)element Atomic

symbol Electronic structure

Melting point /C

Boiling point/C

Densityg/cm3

Atomic radius/pm

Lithium Li 2,1 180 1330 0.53 152Sodium Na 2,8,1 98 892 0.97 186Potassium K 2,8,8,1 64 760 0.86 231Rubidium Rb 2,8,18,8,1

a)i The properties of rubidium are missing from the above tablewhich one of the properties of elements does not show a definite trend?(ii) predict numerical values for the other three properties of rubidium.Write answers in your table.b) what common feature of electronic structure of the group I elements is responsible for their chemical properties being similar? Comment This question generated a wide range of marks.ai) Having correctly identified density as having no definite trend ,this did not prevent some candidates from giving an estimate for the density in the table.ii) Estimation of these figures proved to be difficult for many.The expected answers were: melting point,30-50C,boiling point 650-750C,radius 280-320pm.b) Failure to answer the question was the main reason for mark loss.Some reference to the quoted electronic structure was required.Answers such as ‘they have the same valency’ miss this point.

Q2) i Complete the following table that describes what happens when aqueous chlorine is added to an aqueous metal halide. (J99/p2/A5b)Aqueous halide observation Names of productsPotassium bromide Colourless solution turns orangePotassium iodide ii) Give the ionic equation for one of the above reactionsb) Chlorine will oxidize aqueous iron(II) chloride to form aqueous iron(III) chloride. Describe how aqueous sodium hydroxide can be used to show that the oxidation has taken place.Comment

(i) The names of the products were often correct but the colour change was rarely scored.Typical errors were to describe aqueous potassium iodide as yellow or brown.

(ii) This equation was rarely scored.A molecular equation does not answer this question.When the ionic equation was attempted,the charges on the ions were

rarely correct, ionic equations,which included spectator ions ,were given credit .

b) This section confused the majority of candidates.The expected answer was that a green precipitate formed with iron (II) and brown with iron(III).Many answers tried to oxidize or reduce the sodium hydroxide or discussed reaction between sodium hydroxide and chlorine.

Q3) Ethanol is manufactured by the reversible reaction between steam and ethane. (J01/p2/B10) C2H4(g) + H2O(g) CH3CH2OH(g)

The position of equilibrium is affected by changes in pressure and temperature.In an experiment ,one mole of ethene was allowed to react with excess steam.The table shows the amount of ethanol in the equilibrium mixture under five different sets of conditions.

Temperature/C Pressure/atm Amount of ethanol at equilibrium/mol

300 50 0.40300 60 0.46300 70 0.55250 50 0.42350 50 0.38

(a) (i) Describe the effect of increasing the pressure on the amount of ethanol at equilibrium.

(ii) is the reaction between ethene and steam endothermic or exothermic?Explain your answer.(iii) which set of conditions (temperature and pressure) will give the lowest rate of reaction?

Comment

(a) (i) This was usually correctly answered(ii) Exothermic was only a little more popular choice than endothermic. Rather than quoting figures or trends from the table,the explanation was frequently an irrelevant account of bond breaking and bond formation.(iii) Although ‘lowest rate’ was printed in bold, many candidates chose 350C and

50 atm, the figures for the lowest yield.

Q4 What is a condenser used for? (J03/p4/q12)CommentCool or change vapours to liquids. An answer stating that it is used to condense vapours was insufficient as it does not explain the meaning of the word, condense.

NOTES

Information for Teachers

Teachers who are about to teach syllabuses in this booklet for the first time should obtain and study the relevant past examination papers and Subject Reports.

NomenclatureThe proposals in ‘Signs, Symbols and Systematics (The Association for Science Education Companion to 5-16 Science, 1995)’ will generally be adopted. Reference should be made to the joint statement on chemical nomenclature issued by the GCE boards. In particular, the traditional names sulphate, sulphite, nitrate, nitrite, sulphurous and nitrous acids will be used in question papers.

It is intended that, in order to avoid difficulties arising out of the use of l as the symbol for litre, use of dm 3 in place of l or litre will be made.

In chemistry, full structural formulae (displayed formulae) in answers should show in detail both the relative placing of atoms and the number of bonds between atoms. Hence – CON H 2 and – C O 2H are not satisfactory as full structural formulae, although either of the usual symbols for the benzene ring is acceptable.

Units, significant figuresCandidates should be aware that misuse of units and/or significant figures, i.e. failure to quote units where necessary, the inclusion of units in quantities defined as ratios or quoting answers to an inappropriate number of significant figures, is liable to be penalised.

SCHEME OF ASSESSMENT

Candidates are required to enter for Papers 1, 2 and either Paper 3 or Paper 4.Paper Type of Paper Duration Marks1 Multiple Choice 1 h 402 Theory 1 h 30 min 753 Practical Test 1 h 30 min 304 Alternative to Practical (written) 1 h 30

Paper 1 Theory (1 h, 40 marks)

A paper consisting of 40 compulsory multiple choice items of the simple ‘direct choice' type. A copy of the data sheet (appendix 2) will be printed as part of this Paper.

Paper 2 Theory (1 h 30 min, 75 marks) consisting of two sectionsSection A will carry 45 marks and will consist of a small number of compulsory, structured questions of variable mark value.Section B will carry 30 marks and will consist of 4 questions each of 10 marks with candidates being required to attempt 3 questions. A copy of the data sheet (appendix 2) will be printed as part of this Paper.

Paper 3 Practical Test (1 h 30 min, 30 marks).

This paper will be marked out of 40 and then scaled to a mark out of 30.Details of the syllabus and requirements for this paper are given in appendix 3.Candidates are NOT allowed to refer to notebooks, text books or any other information inthe practical examination.

Paper 4 Alternative to Practical (1 h, 30 marks).

This paper will be marked out of 60 and then scaled to a mark out of 30.A written paper of compulsory short-answer and structured questions designed to test familiarity with laboratory practical procedures.Questions may be set requiring candidates to:(a) record readings from diagrams of apparatus;(b) describe, explain, comment on or suggest experimental arrangements, techniques andprocedures;(c) complete tables of data and/or plot graphs;(d) interpret, draw conclusions from and evaluate observations and experimental (including graphical) data;(e) describe tests for gases, ions, oxidising and reducing agents and/or draw conclusionsfrom such tests;

Candidates may also be required to perform simple calculations.

TOPICS RELATED TO APPLICATIONS OF CHEMISTRY

It is important that, throughout the course, attention should be drawn to:(i) the finite life of the world's resources and economic and environmental issues relating to recycling, renewable energy and conservation;(ii) economic considerations in the chemical industry, such as the availability and cost of raw materials and energy;(iii) the social, environmental, health and safety issues relating to the use of chemicals in the laboratory, in the home and in industry;(iv) the importance of chemicals in industry and in everyday life.

5 ENERGY FROM CHEMICALS(1) describe hydrogen, derived from water or hydrocarbons, as a potential fuel for use infuture, reacting with oxygen to generate electricity directly in a fuel cell (details of theconstruction and operation of a fuel cell are not required) and discuss the advantagesand disadvantages of this.

(2)describe photosynthesis as the reaction between carbon dioxide and water in thepresence of chlorophyll, using sunlight (energy) to produce glucose and explain howthis can provide a renewable energy source.

7.3 PROPERTIES AND USES OF AMMONIA(1) describe the use of nitrogenous fertilisers in promoting plant growth and crop yield

(2) describe eutrophication and water pollution problems caused by nitrates leachingfrom farm land and explain why the high solubility of nitrates increases theseproblems

(3) describe the displacement of ammonia from its salts and explain why adding calciumhydroxide to soil can cause the loss of nitrogen from added nitrogenous fertilizer

(4) state the uses of sulphuric acid in the manufacture of detergents and fertilisers; andas a battery acid

9.3 Extraction of metals

(1) describe metal ores as a finite resource and hence the need to recycle metals(2) discuss the social, economic and environmental advantages and disadvantages ofrecycling metals e.g. aluminium and copper

9.5 Aluminium

(1) state the uses of aluminium and relate the uses to the properties of this metal and itsalloys, e.g. the manufacture of aircraft; food containers; electrical cables

10 ATMOSPHERE AND ENVIRONMENTAIR(1) discuss some of the effects of these pollutants on health and on theenvironment(2) the poisonous nature of carbon monoxide(3) the role of nitrogen dioxide and sulphur dioxide in the formation of ‘acid rain’ andits effects on respiration and buildings(4) discuss the importance of the ozone layer and the problems involved with the depletion of ozone by reaction with chlorine containing compounds,chlorofluorocarbons (CFCs)(5) state that carbon dioxide and methane are greenhouse gases and may contribute toglobal warming, give the sources of these gases and discuss the possibleconsequences of an increase in global warmingWATER(1) discuss the environmental effects of the dissolved substances named in (a)(2) beneficial, e.g. oxygen and mineral salts for aquatic life(3) pollutant, e.g. hazards to health; eutrophication11 ORGANIC CHEMISTRY

(1) describe the issues relating to the competing uses of oil as an energy source and asa chemical feedstock(2 state some commercial uses of esters, e.g. perfumes; flavourings; solvents(3) state some typical uses of man-made fibres such as nylon and Terylene, e.g.clothing; curtain materials; fishing line; parachutes; sleeping bags(4) describe the pollution problems caused by the disposal of non-biodegradable plastics

Teachers training workshop

OL Chemistry: Miss Sumaira AliBahria College Islamabad

15th May 2004

Workshop Programme

Session 1

IntroductionAims and Objectives of trainingScheme of assessmentTopics related to applications of chemistryTeaching strategies( rate of reaction curves)Teaching materials(Worksheets e.t.c)Past paper questions and comment from subject report

Session 2

5070/4 A.T.P QuestionsDiscussionQuestions about 5070Feedback

RESOURCE LIST – 5070

Teachers may find reference to the following books helpful.

*Chemistry by R. Harwood, published by Cambridge University Press (ISBN 0-52157628-8)Chemistry for IGCSE by A. Clegg, published by Heinemann (ISBN 0-435-96675-8)Chemistry Counts by G. Hill, published by Hodder and Stoughton (ISBN 0-340-63934-2)Thinking Chemistry (GCSE Edition) by Lewis and Waller, published by Oxford University Press (ISBN 0-19-914257-2)Chemistry by B. Earl and L. D. R. Wilford, published by John Murray (ISBN 0-7195-5303-2)

These titles represent some of the texts available at the time of printing this booklet. Teachers are encouraged to choose texts for class use which they feel will be of interest to their students and will support their own teaching style.The book marked with an asterisk is also available from Cambridge University Press in a Low Priced Edition (ISBN 0-521-66662-7) from their local distributors in Africa, The Caribbean,Bangladesh, India, Nepal, Pakistan and Sri Lanka. For a full list, or details of distributors in your local area, please contact Mark Ellwood at CUP (mellwood@cambridge.org, tel: +44 1223 312393, fax: +44 1223 315052).

Online resources

Website address

Chemsoc : www.chemsoc.org

RSC and CVC : www.rsc.org/is/cvc/cvc_un16/un16_fp.htm

The Chemists: www.chemclub.com/teachers

The Chemistry video consortium: www.soton.ac.uk/~chemweb/cvc/