level 3 chemistry (91390) 2017 - nzqa...(b) explain why the solubility of hydrazine in water is...
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913900
3SUPERVISOR’S USE ONLY
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© New Zealand Qualifications Authority, 2017. All rights reserved.No part of this publication may be reproduced by any means without the prior permission of the New Zealand Qualifications Authority.
ASSESSOR’S USE ONLY
TOTAL
Level 3 Chemistry, 201791390 Demonstrate understanding of thermochemical
principles and the properties of particles and substances
2.00 p.m. Wednesday 15 November 2017 Credits: Five
Achievement Achievement with Merit Achievement with ExcellenceDemonstrate understanding of thermochemical principles and the properties of particles and substances.
Demonstrate in-depth understanding of thermochemical principles and the properties of particles and substances.
Demonstrate comprehensive understanding of thermochemical principles and the properties of particles and substances.
Check that the National Student Number (NSN) on your admission slip is the same as the number at the top of this page.
You should attempt ALL the questions in this booklet.
A periodic table is provided on the Resource Sheet L3–CHEMR.
If you need more room for any answer, use the extra space provided at the back of this booklet and clearly number the question.
Check that this booklet has pages 2 – 11 in the correct order and that none of these pages is blank.
YOU MUST HAND THIS BOOKLET TO THE SUPERVISOR AT THE END OF THE EXAMINATION.
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QUESTION ONE
(a) Complete the following table.
Symbol of
particle
Electron configuration (use s, p, d notation) Charge Atomic number
Cl 0
+2 20
Mn2+
(b) (i) Definethetermelectronegativity.
(ii) Explainwhytheelectronegativityofchlorineisgreaterthanthatofphosphorus.
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(c) ThefollowinggraphshowsthefirstionisationenergiesoftheGroup2elementsfromBetoBa.
Be400
500
600
700
800
900
1000
Mg Ca Sr Ba
Element
Firs
t ion
isat
ion
ener
gy /
kJ m
ol–1
First ionisation energies of Group 2 elements
(i) Writeanequationtoshowthefirstionisationenergyfortheelementcalcium.
(ii) ExplainthetrendshownoffirstionisationenergiesoftheGroup2elements.
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QUESTION TWO
Molecule Boiling Point / °C M / g mol–1
Hydrazine,N2H4 114 32Iodomethane,CH3I 42.4 142Decane,C10H22 174 142
Usetheinformationinthetableabovetocompareandcontrasttheboilingpointsofthesubstancesbelow.
Inyouranswers,youshould:
• listthetypesofintermolecularforcespresentforeachsubstance
• explaintherelativestrengthbetweentheparticlesinvolved.
(a) (i) Hydrazineandiodomethane.
(ii) Iodomethaneanddecane.
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(b) Explainwhythesolubilityofhydrazineinwaterisgreaterthanthatofdecaneinwater.
(c) Carbondioxideandwaterareformedwhendecaneburnscompletelyinoxygen.Thereactionisshownintheequationbelow.
C10H22() + 15 1
2 O2(g) →10CO2(g) + 11H2O()
Calculatetheenthalpyofcombustionfordecane,giventhefollowingdata:
ΔfH° (C10H22(ℓ)) = –301 kJ mol–1
ΔcH° (C) = –393 kJ mol–1
ΔcH° (H2) = –286 kJ mol–1
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(d) Thereactionforthecompletecombustionofhydrazineisshownintheequationbelow.
N2H4() + O2(g) → N2(g) + 2H2O(g)
Thisisanexothermicreaction. Explaintheentropychangesassociatedwiththisreaction.
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QUESTION THREE
Chlorine,Cl2,bromine,Br2,andiodine,I2,areallhalogens.Bromine isaliquidatroomtemperature.
(a) (i) Intheboxbelow,tickthetype(s)ofintermolecularattractionsinliquidbromine.
Intermolecular attraction Tick (✔)
Temporarydipole-dipoleattractionsPermanentdipole-dipoleattractionsHydrogenbonding
(ii) Explainwhybromineisaliquidatroomtemperature,whereaschlorine isagas.
(b) (i) Writeanequationforthesublimationofiodineintheboxbelow.
(ii) Definetheenthalpyofsublimationforiodine.
Question Three continues on the following page.
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(iii) Explainwhythesublimationofiodineisspontaneous,eventhoughtheenthalpyofsublimationisapositivevalue.
(c) IodineformsalinearI3– ion.
(i) DrawtheLewisstructurefortheI3– ion in the box below.
(ii) ExplainwhytheI3–ionhasalinearshape.
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(iii) IF5hasasquarepyramidalshape.
IndicatewhetherthemoleculeIF5ispolarornon-polar.
Circleyourchoice. polar non-polar Justifyyourchoice.
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QUESTION NUMBER
Extra paper if required.Write the question number(s) if applicable.
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QUESTION NUMBER
Extra paper if required.Write the question number(s) if applicable.
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