9701_s05_qp_2

General Certificate of Education

Advanced Subsidiary Level and Advanced LevelCHEMISTRY

Paper 2 Structured Questions AS Core

9701/02

May/June 2005

Candidates answer on the Question Paper.Additional Materials:Data Booklet

1 hour 15 minutes

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The number of marks is given in brackets [ ] at the end of each question or part question.You may lose marks if you do not show your working or if you do not use appropriate units.A Data Booklet is provided.You may use a calculator.

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For Examiner’s Use12345TOTAL

This document consists of 10printed pages and 2blank pages.SP (MML 8078 3/04) S92060/2.1©UCLES 2005[Turn overwww.xtremepapers.net2

Answer allthe questions in the space provided.Iron and cobalt are adjacent elements in the Periodic Table. Iron has three main naturallyoccurring isotopes, cobalt has one.(a)Explain the meaning of the term isotope.........................................................................................................................................................................................................................................................................................................................................................................................................................[2](b)The most common isotope of iron is 56Fe; the only naturally occurring isotope of cobaltis 59Co.Use the Data Bookletto complete the table below to show the atomic structure of 56Feand of 59Co.number ofisotopeprotonsneutronselectrons56Fe59Co[3](c)A sample of iron has the following isotopic composition by mass.isotope mass5657% by mass5.8491.682.17(i)Define the term relative atomic mass.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(ii)By using the data above, calculate the relative atomic mass of iron to threesignificant figures.[5][Total: 10]©UCLES 20059701/02/M/J/05

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Sulphur and its compounds are found in volcanoes, in organic matter and in minerals.Sulphuric acid, an important industrial chemical, is manufactured from sulphur by theContact process. There are three consecutive reactions in the Contact process which areessential.(a)Write a balanced equation (using where appropriate) for eachof these reactionsin the correct sequence.1 .......................................................................................................................................2 .......................................................................................................................................3 .................................................................................................................................[4](b)What catalyst is used?....................................................................................................................................[1]Hydrogen sulphide, HHydrogen sulphide is covalent, melting at –852S, is a foul-smelling compound found in the gases from volcanoes.°C and boiling at –60°C.(c)(i)Draw a ‘dot-and-cross’ diagram to show the structure of the H2S molecule.(ii)Predict the shape of the H2S molecule..............................................................(iii)Oxygen and sulphur are both in Group VI of the Periodic Table.Suggest why the melting and boiling points of water, H2O, are much higher thanthose of H2S.................................................................................................................................................................................................................................................................................................................................................................................................[4]©UCLES 2005

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Hydrogen sulphide burns with a blue flame in an excess of oxygen to form sulphur dioxideand water.(d)

(i)Write a balanced equation for the complete combustion of H2S.

..................................................................................................................................(ii)What is the change in the oxidation number of sulphur in this reaction?

from .......................................................to .............................................................(iii)What volume of oxygen, measured at room temperature and pressure, is required

for the complete combustion of 8.65g of Hplaces.

2S? Give your answer to two decimal[5]

Hydrogen sulphide is a weak diprotic (dibasic) acid. Its solution in water contains HS–and afew S2–ions.(e)

(i)What is meant by the term weak acid?

....................................................................................................................................................................................................................................................................(ii)Write an equation, with state symbols, for the firstionisation of Hdissolves in water.

2S when it

............................................................................................................................[3]

[Total: 17]

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3Magnesium is the eighth most common element in the Earth’s crust.The metal is widely used in alloys which are light and strong.Some reactions of magnesium and its compounds are shown in the reaction schemeForExaminer’sUsebelow.H2(g)+A(aq)dil. H2SO4Mg(s)dil. HClB(aq)+H2(g)Na2CO3(aq)heat in airNaOH(aq)C(s)heatD(s)heatE(s)heatdil. HNO3F(s)evaporateF(aq)(a)Identify, by name or formula, compounds Ato F.A.......................................................B.......................................................C.......................................................D.......................................................E.......................................................F........................................................©UCLES 2005

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(b)

(i)Construct balanced equations for the following reactions.

magnesium to compound A

..................................................................................................................................compound Cto compound D

..................................................................................................................................compound Fto compound D

..................................................................................................................................(ii)Suggest a balanced equation for the effect of heat on compound E.

............................................................................................................................[4]

[Total: 10]

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Compound G, in which R– represents the rest of the molecule, was made for use as a teargas in World War 2.HRCCNBrcompound GCompound Gwas made by the following sequence of reactions.R–CHstage Istage II3R–CH2ClR–CH2CNstage IIIR–CHBrCN(a)(i)For stage I andfor stage II, state the reagent(s) and condition(s) used to carry outeachchange.stage Ireagent(s) ..................................................................................................condition(s) ................................................................................................stage IIreagent(s) ..................................................................................................condition(s) ................................................................................................(ii)Suggest the reagent(s) and condition(s) necessary to carry out stage III.reagent(s) .................................................................................................................condition(s) ...............................................................................................................[6]©UCLES 2005

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Compound Gwas not actually used in World War 2 and stocks of it had to be destroyedsafely. The following sequence of reactions was used in this process.R–CHBrCNstage IVR–CHBrCOstage V2HR–CH(OH)CO2Hstage VIR–CH2CO2H(b)For stage IV andfor stage V state the reagent(s) and condition(s) necessary to bringabout eachreaction.stage IVreagent(s) .........................................................................................................condition(s) ......................................................................................................stage Vreagent(s) .........................................................................................................condition(s) ................................................................................................[4](c)The full sequence of stages I to VI involves some compounds which contain chiralcentres.(i)Explain what is meant by the term chiral centre.....................................................................................................................................................................................................................................................................(ii)Draw displayed formulae for the isomers of onecompound in the full sequence ofstages I to VI which you consider to be chiral.[3][Total: 13]©UCLES 2005

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A student obtained the following results when analysing an organic compound, H.testobservationtest 1relative molecular mass72test 2% composition by massC, 66.7%; H, 11.1%; O, 22.2%test 3reactions with Br2(aq)Br2decolourisedtest 4reaction with Na(s)H2(g) evolvedtest 5reaction with warm Cr2O2–7/H+green colour observedThe student allowed test 5 to go to completion and then investigated the productof test 5with the following result.test 6reaction with 2,4-dinitrophenylhydrazineno reaction(a)Calculate the molecular formula of H.[2](b)What can be deduced about the nature of Hby the following tests?(i)test 3 ........................................................................................................................(ii)test 4 ........................................................................................................................[2](c)(i)What functional group would have given a positive result in test 6?..................................................................................................................................(ii)What functional group is shown to be present in Hby tests 5 and 6?..................................................................................................................................[2]©UCLES 2005

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(d)On testing a sample of H, the student found that it was not chiral.

Hdid, however, show cis-transisomerism.

How does cis-transisomerism arise in an organic molecule?

........................................................................................................................................................................................................................................................................................................................................................................................................................[2](e)Use all of the information above to draw labelled, displayed formulae of the

stereoisomers of compound H.

[2]

[Total: 10]

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