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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.

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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