OCRf
RECOGNISING
ACHIEVEMENT
OXFORDCAMBRIDGEAND RSA EXAMINATIONS
Advanced SubsidiaryGCE
2811
CHEMISTRY
Foundation
Chemistry
Friday
17 JANUARY2OO3
t hour
Morning
Candidatesansweron the questionpaper.
Additionalmaterials:
Scientiticcalculator
Data Sheetfor Chemistry
CandidateName
TIME
Candidate
Number
CentreNumber
t hour
TO CANDIDATES
INSTRUCTIONS
.
Writeyour name in the space above.
r
Writeyour Centrenumberand Candidatenumberin the boxesabove.
Answerall the questions.
Writeyour answersin the spaceson the questionpaper.
.
.
o
Read each questioncarefullyand make sure you know what you have
to do beforestartingyour answer.
FOR CANDIDATES
INFORMATION
.
T h e n u m b e ro f m a r k s i s g i v e n i n b r a c k e t s[ ] a t t h e e n d o f e a c h
questionor partquestion.
You will be awardedmarks for the qualityof writtencommunication
wherethis is indicatedin the question.
USE
FOREXAMINER'S
Qu.
Max.
1
12
a
You may use a scientificcalculator.
You may use the Data Sheet for Chemistry.
a
You are advisedto show all the steps in any calculations.
2
17
3
14
4
I
5
9
TOTAL
60
a
Mark
This questionpaperconsistsof 10 printedpagesand 2 blankpages.
MML 2940 310253446714
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[Turnover
2
For
Examinel
Use
Answerall the questions.
Gallium,atomicnumber31, existsnaturallyas a mixtureof its isotopes,6eca
and 71Ga.
(a) Completethe table below to show the atomicstructureof each isotopeof gallium.
numberof
isotope
protons
neutrons
electrons
6eGa
71Ga
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(b) A mass spectrometercan be used to identifythe isotopesin a sample of an element.
The diagrambelow shows a mass spectrometer.
Completethe diagram by adding the names of the processesthat take place in each
of the four labelledregions.
to the pump
vapour of ,r,
element
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3
(c) A sample of gallium was analysedin a mass spectrometerto produce the mass
spectrumbelow.The relativeatomic mass of galliumcan be calculatedfrom this mass
For
Examinels
Use
spectrum.
100
c
.9
.=
U)
o
oE
o
()
60
.-e
70
75
relativeisotopicmass
(i) Define the term relativeatomic mass.
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(ii) Estimatethe percentagecompositionof each isotopepresentin the sample.
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(iii) Calculatethe relativeatomicmass of this sampleof gallium.Your answershould
figures.
be givento threesignificant
answer
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[Total : 12]
[Turnover
For
Examine/
Use
4
2
When magnesiumis heatedin air,it reactswith oxygento form magnesiumoxide.
2Mg(s) + or(O) -+
2MgO(s)
of a magnesiumatom.
(a) Completethe electronicconfiguration
1s2
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(b) What is the oxidationstateof magnesiumin
(i) Ms
(ii) Mgo?
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(c) When magnesiumis heatedin air, it also reactswith nitrogento form solidmagnesium
nitride,MgsNz.
(i) Constructan equation,with state symbols,for this reactionbetweenmagnesium
and nitrogen.
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(ii) Suggestwhy magnesiumreactswith air to form muchmore MgO than MgsNz.
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(d) Magnesiumoxide has an extremelyhigh meltingpoint which makes it suitableas a
liningfor furnaces.
Explain,in termsof its structureand bonding,why magnesiumoxidehas this property.
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5
(e) When magnesiumoxide is added to warm dilute nitric acid, a reactiontakes place
forminga solutionof magnesiumnitrate.
MgO(s) + eHNor(ac) -+
For
Examinels
Use
Mg(NOr)r(aC)+ H2o(l)
A studentreacted0.0500mol MgO with 0.400moldm-3 nitricacid.
(i) What wouldyou see duringthis reaction?
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(ii) Calculatethe mass of MgO that reacted.
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(iii) Calculatethe volume of 0.400moldm-s HNO. requiredto react exactlywith this
amountof MgO.
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(f) The solutionformedin this reactioncontainsions.
(i) Why does this solutionconductelectricity?
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(ii) Statethe formulaeof two ions presentin this solution.
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[Total: 17]
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6
3
For
Examine
Use
This questionis aboutchlorineand chlorinecompounds.
(a) Chlorinereactswith water to form a solution.
c t r ( O )+ H 2 O ( l ) + H C l ( a q )
+HOCI(aq)
(i) Why is chlorineaddedto wateron a largescale?
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(ii) Greenuniversalindicatoris addedto this solution.
What colourchangeswouldyou see
immediately.
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aftersome time?
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(b) Describea simple test that you could carry out to show that chlorideions are present
in a sampleof sea water.
reagent
obseruation .
equation
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(c) Some dry-cleaningsolventsincludethe chlorinecompoundPerc.
Perc has the followingpercentagecompositionby mass:Cl, 85.6%;C,14.4"/".
The relativemolecularmass of Perc is 166.
(i) Calculatethe molecularformulaof Perc.
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(ii) Suggestwhy Percwouldnot reactin the testin (b).
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For
Examiner's
Use
7
(d) Sodiumchlorate,NaClO3,is a chlorinecompoundusedas a weed killer.
When heated,NaCtO, releasesoxygengas.
zNaClO.(s) -+
2NaCl(s;+ 302(9)
Calculatethe volume of O, that can be formed at room temperatureand pressureby
heating4.269 of NaCtOr.
at roomtemperatureand pressure.
1 mol of gas moleculesoccupies24.Odm3
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[Total: 14]
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I
4
The first six successiveionisationenergiesof an elementD are shown in Table4.1 below.
Table 4.1
ionisationenergy/kJ mol-1
element
D
1st
2nd
3rd
4th
5th
6th
1086
2353
4621
6223
37832
47278
(a) Definethe term first ionisationenergy.
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(b) Write an equation,with state symbols,to representthe third ionisationenergy of
elementD.
t2)
(c) Use Table4.1 to deducewhichgroupof the PeriodicTablecontainselementD.
Explainyouranswer.
group
explanation
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[Total: B]
2811Jan03
For
Examine/s
Use
I
5
For
Examine/s
Use
In this question,one markwill be awardedfor the qualityof writtencommunication.
In the PeriodicTable,describeand explainthe trend in atomicradiishown by
o
the Group2 elementsBe-Ra
o
the Period3 elements,Na-Ar.
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Qualityof WrittenCommunicationt1l
lTotal : 9]