i-(9

o-m

READ THESE ]NSTRUCTIONS FIRST

Write your name, register number and class in the spacos provided above.Write in dark blue or black pen.DO NOT use staples, highlighters, glue or correction fluid/lape.

Answer all questions.

Each questlon consisls of four possible answers. Select lhe most appropriate answer andshade its alphabet on the OTAS sh€et using a soft 2E} pe4cll.

Each correct answ€r will be awarded 1 mark. No marks will be deducted for incorrect answers.

The total marks for this paper is 40.

The Periodic Table is provided on page 12.

1. The table below shows some properlies of chlorine and hydrogen chloride.

chlorinenature of oas acidic acidic

solubilitv in water sllqhtly solubl6 very soluble

A dry sample of chlorine can bs separated from a mixture of chlorine and hydrogenchloride using the experimental setup shown below.

chlorinemixture of chlorine and

hydrogen chloride

x Y

What are the idenlities of solulions X and Y?

x YA sodium bromide calcium chlorideB sulfuric acid calcium chloridec sodium hydroxide concentrated sulfuric acidD water concenlrated sulfuric acid

2. Aqueous ammonia reacts with a colourless solution tg produce a precipitate. What couldbe the identlty of the colourless solution?

A calcium nitrateB hydrochloric acidC sodium carbonateD zinc sulfale

3- When the glass plate is removed from the gas jar, lhe colour of the gas is the same forboth jars after several days as shown in the diagram below.

gas jar

100% air 50% air + 50% bromlne

glass plate glass ptate removed

100% bromine 50% air + 50% bromine

NEW TOWN SECONDARY SCHOOLPreliminary ExaminationSecondary 4 Express

NAME

CLASS INDEXNUMBER

ChemistryPaper 1

Additional Materials:

50731015 August 201 6

0800-0900'l hour

OTAS

start ofexperiment

2

after afew days

This document consisls of 12 printed pages.S6tt8n Mr Mohamad Khksyaban

gas jar

1

DANYAL EDUCATION

4.

Which statement best explains tha apPearance after a few days?

A Heavier particles sink while lighter particles rise-

B Both the air and bromine particles difiuse at the same rate'

G There are as many gas particles as bromine particles in each jar'

D Both the air and bromine particles move randomly-

A beam of particles containlng electrons is passed. through charged plates. which path

shows how the electrons move through the plates?

9, The diagram shows the arrangement of ions in an ionic crystal'

! positive ion

negative ion

Which compound cannot have this arrangement of its ions?

A calcium oxide, CaOB copper (ll) sulfate, CuSOrC iron (lt) chloride, FeC/e

D zinc carbonate, ZnCOr

10. Element X has the electronic structure 2.7 while element Y has the electronic structure

2.8.6. What is the likely formula of the compound containing X and Y?

AXYB XaYC XYzD XrYe

11. Which feature of calcium's structure is responsible for conductlon of elechicity?

A ll has a lattice of Positive ions.B lls positive ions atlract electrons.C lt ij made up of free-moving positive and n€gative ions.D lt conlains a 'sea of valence electrons'.

12. Sodium oxalate has the formula NazCzOr while niobium chloride has the formula NbC/r.

What is the formula of niobium oxalate?

A NbaCzOrB NbgCzO+C Nbz(CzOrhD Nbr(CzOa)z

13. Which of the following has lhe same Mr as calcium silicate. CaSiOr?

AIzOsNaNOgMsoFeCOs

positive Plate

-

5.

A electrons.B neutrons.c nucleons.D protons.

6. Which statement shows lhat an unknown substance X is an element?

A X decomposes when healed to form oxygen gas'

B X burns in oxygen to form an oxide as the only product'

C X melts at a fixed temPerature.D X does not react when exposed to oxygen.

7. Which statements apply to both diamond and graphlte?

l: contains onlY carbon atomsll: covalently bonded lo other atomsllt: giant molecular structure

A I and ll onlyB I and lll onlYC ll and lll onlY

D I, ll and lll

g. The hydrogen atom can form ionic bonds with element Y. What could be element Y?

calciumchlorinenitrogonsulfur

A

B

c

D

The ions fls a anO llct - trave the same number of

ABcD

ABcD

3

@-o

c',@

4

negative plato

DANYAL EDUCATION

battery

CUSOr

bulb

NaCl (aq)

O)(9

o-c0

14. Three circuits are set up as shown below,

ln how many of the circuits above does electrolysis take place?

A1 82C315. What happens when molten sodium oxide ls electrolysed?

18, ln an experiment, an excess of zinc reacts with 200 cm3 of 0.1 mol/dm3 of hydrochloricacid. The graph shows how the volume of hydrogen produced varies with time.

ln a second experlment, the same mass of zinc reacts with 100 cm3 of 0.2 mol/dm3 ofhydrochloric acid. For the second experiment. at which point will lhe graph becomehorizontal?

Volume ofhydrogen

A

B

./c ./ D

,l/

/ T me

/

D4

Sodium ions lose an electron at the cathode.Oxide ions gain electrons at the cathode.Sodium ions gain an electron at the cathode.Oxide ions lose electrons at the cathode.

16. ln which eleclrolysis experiment would there be no change in lhe concenlralion of lhesolution?

elcictrolvte electrodesABcD

dilute hydrochloric acidaqueous sodium chloride

aqueous copper (ll) nitrateconcentrated aqueous iron {ll) chloride

carboncarboncoppercopper

17. When a magnasium strip was dropped into excess hydrochloric acid, the rate of reactionincreased for the first few seconds. What could be a possible explanatlon for lhis increase?

A The mass of magnesium increased a$ the reaction proceeds.B The reaction between magnesium and hydrochloric acid is exothermic.C The magnesium acts as a catalyst for this reaction.D The volume of magnesium decreases as the reaclion proceeds.

19. Which equation does not represent a redox reaction?

A Ca2'(aq) + SOr2-(aq) ) CaSOr (s)B Brz (g) + 2 f @ql) 2 Br(aq)+ 12 (s)C Clz (S) + 52- (aq) ) S (s) + 2 Ct (aq)D Fez'(aq) + Zn (s) ) Zn2'(aq) + Fe (s)

20. To grow well, plants require neutral or slightly alkaline soil and nitrogen found in the soil.However, acid rain may cause lhe pH of soil to drop-

Whlch of the followlng fertilisers should be used to grow plants on soil affected by acidrain?

Fertiliser ComponentsABcD

Ca(OH):, NHrCICa(OH)2, NaNOrCa(NOr)a, HNOr

Ca(NOs)2, (N&)zSOr

ABcD

o5

botlery

bulb

CUSOr

I

DANYAL EDUCATION

28. The composition ol elements in four substances is shown in the pie charts below. Which of

the following does not show the composilion of alloys?21. Aqueous barium chloride Is a colourless solution. Which substance when added to

aqueous barium chloride gives a colourless solulion?

A ammonlum sulfateB lead(ll) nitrateC silver sulfateD zlnc nitrate

22. Under appropriate conditions, sulfur dioxide and oxygen react to form sulfur trioxide as

shown bY the equation below.

2 SOz (g) + oz (g)i"+ 2 SOs (g)

which statemont is talse about the sample of gas at lhe end of lhe roaction?

A lt turns blue cobalt (ll) chloride crystals pink.

B lt turns purple acidified potassium manganate (Vll) colourtess.

C lt turns moist blue litmus paper red'D lt rekindles a glowing splint'

23. The graph shows how a factor X changes from aluminium to potassium in the Periodic

Table.

Element

BA

Dc

What could X be?

alomic sizeproton numberrelative alomic massnumber of valenc€ electrons

24. Element R has the following properties.

What type of element is R?

alkali metalhalogennoble gastransition metal

It has a high melting Polnt.Its presence can lower the activation €nergy of a reaction'

26. Which oxide can be reduced to the metal using hydrogen?

A calcium oxldeB lead (ll) oxideC sodium oxideD zinc oxide

27. Which of the following does not produce carbon dioxide?

A hsaling Potassium carbonateB adding dilute hydrochloric acid to coppe(ll) carbonateC burning methane in excess oxYgenD fermentalion of glucose

28. Why is recycling of metals encouraged in Singapore?

A Extracting metals is an expensive process'B Toxic gases are glven off during recycling.C Recycling metals uses up a lot of raw materials'D lt is tedious to separate metals from non'metals.

29, Why is stainless steel used to make surgical instrumenls?

A lt ls easilY shaPed.B lt is hard and brittle.C lt is a good conductor of electricity.D lt is resistant to corrosion.

x

AlsiPScrArX

ABcD

ABcD

7

wT{o

8DANYAL EDUCATION

oa

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30. Which of the following 'dot-and-cross'diagrams represents a gas that is not present in dry,clean air? (Only the valence electrons are drawn)

A

31 . Which of the following gases cannot be removed from ths exhaust gases of a pelrolpowered car by its catalytic converter?

A carbon dioxideB carbon monoxideG hydrocarbonsD nitrogen dioxide

32. The global atmospheric concenlralion of carbon dloxlda hps increased In the last 200years. What could be causing this change?

l: emissions from moior vehiciesll: photosynthesislll: power stations using oll

A I and ll onlyB land lll onlyC ll and tll onlyD l. ll and lll

33. ln how many of the following is kerosene used as lhe onergy sourc6?

alrcraft carsdomesticcookino

powerslations

A1B2c3D4

34. Which compound has molecular formula CsHsO?

ethaneethanoic acidpropanolpropanoic acid

35. The motecular structure of a hydrocarbon ls shown below.

H

,-lH

IIH

H

H

Which shucture is an isomer of this hydrocarbon?

I

HHHHtlllH

- C-C-C-C-HrlllHHHH

HH

H

IC

IH

Dc

H-

H

Ic -*H

BA

HIH

t_1t_,rlHHH

H

Ic-H

H

H_ TTc-c-H

H-

I

-cI

H

H

Ic

I

H

IH D

IH

HH

H

-o-HH- H

IH

I

HIH

36. What reagsnts are ns€ded to convsd ethanol to ethanoic acid?

warm with acidilied potassium manganate (Vll)37 oC, yeast and air-tightadd to sodium carbonate solutionhydrogen gas, nickel as catalyst

ABcD

ABcD

9 10

B

c

DANYAL EDUCATION

37. The dlagram bolow shows lhB structure of an organic compound.

HHHHHHHHtf tlrlll

c-c-c-c-c-clrllllHHHHHH

0

E lrlt

":_)"1-i={ -t-+

tl //-c\n

OHIt rt

It h 4

Which statement about this organic compound is true?

A lt is an alcohol.B lt is a hydrocarbon.C lt is a macromolecule.D lt is a polyunsaturated compound.

38. Which of the following similarities and differences between ethene and poly(ethene) are

correcl?

Similarity DifferenceABcD

Products of combuslionReaction with bromine

Relative molecular massElectrical conductivitY

Reaction with bromineBoiling point

Electrical conductivityProducts of combustion

39, An ester has the struclure as shown.

HOHlillc-c-o-c-HtlHH

Which compounds form the ester above?

A elhanol and methanoic acidB elhanol and ethanoic acidC methanol and ethanoic acidD methanol and melhanoic acid

40. Which of the following statements is not true about nylon?

A lt is formed by condensation polymerization.B The monomers are linked by amide linkages.C lt is non-biodegradable and causes pollution.D One of its monomers is an alcohol.

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SECTION AAnswer alt the questlons in this section in the spaces provided.

The total mark for this section is 50.

A1 The following diagram shows an outline of the Periodic Table of Elements.

Using the letters A to E, show the position of the following elements on the diagram above.

A - the element with 28 protonsB - the halogen wlth the highest melting pointC - the least reactive alkali metalD - the element with electronic conriguration 2.8.8E * the element mixed with iron to form steel

A2

NEW TOWN SECONDARY SCHOOLPreliminary ExaminationSecondary 4 Express

NAME

CLASS INDEXNUMBER

ChemistryPaper 2

5073t0229 July 2016

0800-0945t hour 45 minutes

READ THESE INSTRUCTIONS FIRST

Write your name, register number and class ln the spaces provlded above.Write in dark blue or black pen.Write your answers on lhe separate answer paper provided.DO NOT use staples, highlighters, glue or correction fluid/tape.

Section AAnswer all questions in the spaces provided

Sectlon BAnswer all three guestions, lhe last question in the form either/or.Answer all questions in the spaces provided.

The number of marks is glven in brackets I t at the end of each question or parl questionThe total marks for this paper ls 80.A copy of ths Periodic Table is prinled on page '16.

The use of an approved scientiflc calculator is expected, where appropriate.

For Examiner's UseSection A

Section B

Total

This docurnent consists of 16 printed pages.Setter Mr Mohamacl Khirsyaban

1

(a)(b)(c)td)(e)

tlln1t11

I11tlI

ftotal: 5 marksj

Ethanol can be produced from the aclioh of yeast on sugars found in grbpes to producewine in 40 days. The graph shows how the composilion of elhanol and grape juice changes.

- grape juice

---- ethanol

volume of1.5 ethanol / dm3

2.

time / days

r

DANYAL EDUCATION

(b) Using lnformation fiom the graph. calculats the percentage of ethanol, by volume,present in wine.

(a) Grape juice is known to conlain glucose. Wilh the help of a chemical equation, explain [3]the changes in composition ol ethanol and grape juice as shown in the graph'

A3 A pupil investigated lhe reaction b€tween powdered magnesium and copper (ll) sulfate as

shown ln the dlagram below.

thermometer

polystyrene cup

50 cm3 copper (ll)sulfate solution

The results of the experiment, uslng dilferent mass of magnesium, are shown in the table

below.

Mass of magnesium / g Maximum tel0.2 3.5o.4 6.00.6 8.00.8 9.01.0 9.0

(a) Write the ionic equation, with state symbols, for the reaction above

(b) using the information given, calculate the concentralion of Guz'ions, in mol/dm3 of

lhe solution.

(c) suggest two observations, othor than a change in temperature, which will happen iff .i!' of magnesium is added to 50 cm3 of the copper (ll) sulfate solution'

12)

(e'l The ethanol concentralion in wine can be determined by titrating a known volume of wine

wiitr a sotution of acidilied potassium manganate (Vll). The ionic equation for the reaction is

4 MnO{ (aq) + 5 CzHsOH (aq) + 12 H* (aq) ) 4 Mn2'(aq) + 5 CHgCOOH (aq) + 11 HzO (I)

i. State the colour change ol acidlfied potassium manganate (Vll) in thls reactlon' I11

lr. Explain, using oxidation stale, why the manganate (vll) ion is reduced ln this reaction. 121

fl-otal: 8 marks]

t21

121

t2)

tpE{cn

54DANYAL E

DUCATION

t-t-o-m

(d) Sketch an energy profile diagram for the reaction. ln your dlagram, label clearly theenthalpy change and actlvation energy.

t3l

ffotal:9 marksl

A4 Hydrogen gas can be produced from water using eleclrolysis. The diagram shows the apparatusthat can be used in the laboratory for lhis electrolysis. '

cathode anode

power

(a) Explain why some hydrochloric acid needs to be dissolved in the water beforeelectrolysis can be carried out.

t21

(b) Name gas A and describe the chemical test to detsrmine lls ldentity. 121

(c) With the help of a half ionic equation, explain the formation of gas B. tzt

(d) With the help of a chemical equation, account for lhe relative volumes of gas A and B. [2]

ffotal: 8 marksl

A5 Hydrogen peroxide solution, HeOa, decomposes to form oxygen and water.

2HzAz)02+2HzO

The reactlon ls very slow at room temperature but can be speeded up by adding certain metaloxlde powder$. which act as catalysts. The rate of reqctlon can be measured by recording thevolumo of oxygen produced over tlme. The following grapho show the volume of oxygen

manganese dioxide

Volume ofoxygenproduced(cm1

copper oxide

zinc oxide

't'ime(s)

(a) Based on the graph, which metal oxide is the best catalyst for the decomposltion ofhydrogen peroxide?

BA

6

nt

5

DANYAL EDUCATION

tb) Explain how catalysts help to spBed up the rate of reaction. t3I

(c) state two other conditions that can speed up the rate of decomposillon of hydrogenperoxide.

tzl

ftotal:6 marks]

A6 The following table shows the colours of universal indicator at different pH values.

colour red oranqe yellow oreen blue purple violet

oH ranqe 0-2 -4 5-6 7 8-9 10-12 13-14

State the colour of universal indicator when it is added to a mixture of sodium oxide

dissolved in water.

carbonic acid turns universal indicator orange whtle nitric acid turns it red. withreference to the table, explain this observation using ideas of acid strength'

A blue solution is suspected to be an alkali. Describe a chemical test that can be

carried out to delermine its alkaline nature.(c) tzl

fl-otal:7 marksl

A7 A group of students were investigating colours in ink. Ihey were given threepuresu-bslances A, B and G, and two mixtures X and Y. They carried out paper chromatography

and produced the chromatogram shown.

solYcnt fiont

f)isratrcc (cm)

t09

s

65

4

37I

0

t1l

t4t

r\B cInk

XY(a)

(b)

(a) what evidence from the chromatogram shows that substances A, B and C are pure? I1l

(b) State the substances present in mixture X.

(c) Calculate the Rr value of the mosl soluble dye in mixture Y

(d) Substance c has a melting point of 119 oC. Estimate, with a reason, lhe approximate l2lmelting Point of X.

t11

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78DANYAL E

DUCATION

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(e) Eesides being used to identify coloured dyes in ink, explain why chromatography isalso used on drugs and food colourings.

tzt H

I

H

I

C

I

flotal: 7 marksl

SECTION B

rhe rast question ,. ,n ,n, r*f3ilflilffi]:nt':,fi:lT$h:T,l':l;$ves shourd be attempted.

88 Read the passage below, which explains the chemistry of how certain foods 'rise' duringcooking.

Manyfood products such as bread, sponge cakes and buns have a honeycomb structurewhichcontains many bubbles. During cooking these bubbles are formed by a gas and the mixture'rises'. ln some cases, the gas is air which is wlripped into the mixture before cooking andexpands during cooking. ln othercases, the gas is carbon dioxide,

The most common chemical to do this is sodium hydrogen carbonate, NaHCOs. Sodiumhydrogen carbonate is found in both baking soda and baking powder.

. Baking soda consists of only sodium hydrogencarbonate. When it is heated, it formscarbon dioxide gas according to the equation:

2 NaHCOs (s) ) NazCOs (s) * COz (S) + HzO (l)

Since the material is relatively che8p, it seems to be an excellent agent for the production ofcarbon dioxide. The above chemical equation, howeveq, also illustrates the disadvantages ofbaking soda. When used on its own, onty hatf the available carbon dioxide is released and moreseriously, the sodium cbrbonale produced gives the baked product a slightly bitter and'soapy'taste. To overcome this problem, baking soda is usually mixad with soma honey.

Baking powder consists of a mixture of sodium hydrogen carbonate and a weak acidsuch as potassium hydrogentartrate (cream of tartar). The formula of thls acld is:

HO

HO

_ cooH

- cooK

Potassium hydrogentartrate is a solid which means that lt is posslble to mix it with sodiumhydrogencarbonate without the two reacting. The reaction is:

HO

-cooHHO_C_COONa

+ CO2 + H2O

Ho_c_cooK HO

-C -COOKH H

One problem with the use ol potassium hydrogentartrate is that it is v€ry soluble in water. So assoon as it becomes wet, it dissolves and reacts. This risks all the gas escaping while the cakemix is still liquid and before it goes into lhe oven.

(a) Using klnetic particle theory, explain how air which has been whipped into the mixtore 121makos the dish'rlse' upon cooking,

(b) Predict the pH value of sodlum carbonate when it ls dlssolved in water. t1I

(c) The average pH of honey is 3.9. Explain how addition of honey to baking soda makes t2)the cake taste better-

(d) Besides taste, explain why most bakers prefer to use baking powder instead of baking [21soda when they are baking cakes.

H

I

C

I

c

I

H

9 10

+ NaHCO, J I

DANYAL EDUCATION

(e) Potassium hydrogentartrate Gan be made from the reaction of potassium hydroxide

with tartaric acid. Draw the structural formula of tartaric acid. t1l

(0 The following instruction is found on a bottla of baking powder'

Store in a drg place

Explaln why this instruction is important- tzt

ffotal: 10 marks]

89 Th6 tablo shows some properties of some elements in Group 0 - the noble gases.

ElementElectronlc

conflouratlonRelative

atomic massDenslty / g

dm'3Meltlng

point / oCBolllng

polnt / oC

Helium 4 o.17 -272 -269

Neon 2.8 20 0.83 -249 -246

Arqon 2.8.8 40 1.67 -189 -1 86

Krypton 2.8.18,8 84 3.50 -157 -152

Xenon 2.8.18.18.8 131 -112 -1 05

(a) using information from the table, suggest why noble gases are unreactive. t2l

(b) Calculate the density of xenon.

(c) All Group 0 elements are gases at room temperature and pressure. state how the

information from the table supports this.

(d) From the data in lhe tabla, describe the structure of a krypton atom.

(e) Xenon has been found to form a compound xenon difluoride. XeFz, which has a

melting point of 128 oc. Using ideas of bonding and structure, explain the meltingpoint of xenon difluoride.

tzt

t11

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t3l

[otal: 10 marks]

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11rzDANYAL E

DUCATION

Eo-E|THEROrro a,uo, the reactions shown below.

elhane

n

PVC

(a) Draw the full structural equation for Reaction I, including any reaclion conditions. t3l

(b) Draw the full structural formula of vinyl chlorlde. tlI

(c) Reaction ll is an addition reaction. Suggest the name of the gas that can be used to tllreact with vinyl chloride [n Reaction ll.

(d) Describe a chemlcal test to distinguish between CHaCHzCi and vinyl chloride. tzt

(e) When CHgCHzC/ is warmed in a mixture of sodium hydroxide and ethanol, thefollowing reaction takes place.

CHgCHzCI + OH- ) CHcCHzOH + Cl

Wlth lhe aid of an ionlc equalion, describe and explain the observation when acidifiedsllver nitrate solutlon is added to the resulting mlxture. t3I

[Total: 10 marksl

OR

810 The following flow diagram shows how ammonium nitrate is rnanufactured from nitrogen,hydrogen and nilric acid.

Reaction I

dissoives in water

Reaction ll

(a) Describe the conditions requked for Reaction I to take place.

(b) Construct the ionic equation with state symbols for Reaction ll.

Reaction t Reaction llcHacHzcl <- vinyl

chloride

polymerlsation

{2)

t2t

nitrogen

ammonia

hydrogen

aqueousammonia

ammoniumnitrate

nitric acid

13 14

DANYAL EDUCATION

(c) Calculate the percentage of nitrogen by mass ln ammonium nitrate- t11

(d) Draw a 'dot-and-cross'diagram to show the bonding in ammonia. l2t

(e) Ammonium nitrate can also be produced from the following reaction'

Ca(Nor)z (aq) + 2 NHs (g) + coz (g)+ Hzo (I) ) 2 NHTNOo (aq) + caCoa(s)

Describe how a pure sample of ammonium nitrate crystals can be obtained from the l3Iproducts of this reaction.

{Total: 10 marksl

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1516DANYAL E

DUCATION

NEW TOWN SECONDARY SCHOOT

PRE LIMINARY EXAMINATION 2015

SECONDARY 4 EXPRESS

CHEMISTRY

PAPER 1

ANSWER SCHEME

Question Answer Question Answer Question Answer Question Answer

1 D 11. D 2L D 3L A

2 D 12 c 22 A 32 B

3 D 13 D B 33 B

4 A 74 c 24 D 34 c

5 A 15 c 25 A 35 B

6 B 16 c 26 B 36 A

D t7 B 27 A 37 D

8 A 18 B 28 A 38 A

9 c 19 A 29 D 39 A

10 B 20 B 30 A 40 D

8/ dE

23

DANY

AL E

DUCA

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NEW TOWN SECONDARY SCHOOT

PRETIMINARY EXAMINATION 2016SECONDARY 4 EXPRESS

CHEMISTRY PAPER 2

29 JULY 2016

A5(a) Man8anese dioxide 1

A5(b) catalysts provide an alternative pathway to the reaction which lowers theactivatlon enerw of the reactlon.Thls results in more particles havinB energy greater than the activationenerty.Thus, there is a higher frequency of effective collisions which speed up therate of reactlon.

1

1

1

As(c) Hlther concentration of hydrogen peroxideHlEher temperature of hydrogen peroxide

t1

A5(a) Vlolet 1

A6(b) Nitric acid is a g[qng acid while carbonic acid is a weak acid.Nltrtc acid !!gg!g!eg fully in water to produce a hiEher concentration ofhydrogen ions.Carbonic acid dissociates partlally in watet to produce a lower ggggq!1a'!!snof hydrogen ions.This leads to nitric acid having a lower pH than carbonic acld.

1

1

1

1

A6(c) Warm the blue solution wlth ammonium chlotlde / sutfate / nitrate.The gas evolved will turo molst red litmus gaper bluir.

x1

A7(a) There is only one spot in the chromatogram for A, B and C. 1

A7(b) AandC 1

a7(c) 9/10=0.9 1

A7(d) 118 oC (accept any answer slightly below 119 oCf 'X ls an lmpure sample of C so the lmpurlties lower the melting polnt of C.

1

1

A7(e) To determine the purlty of the drug, and food coloqrlngs.So that it wilt be safe for consumptlon. i '

It

88(a) At hither temperature, the air particles gain enerigy and move faste..The particles move further from each other lnc.easiirE the volume oI air.

1

1B8(b) 8 (accept pH value 8 - 10) 1

B8(c) Honey ls an acldlc substance.It reacts wlth sodlum carbonate, removinp lts bltter taste from the cake.

1

1

B8(d) Using baking soda produces twice the volume of COr compared to bakinBpowder. :

This will make the cakes that they are baking rise hicher.

1

1

B8(e) HIcIcIE

EO-go-

-coon

-cooE

1

88(f) Potassium hydrogentartrate produces hydrogen ions when dissolved in water,When dry no hydrogen ions are present so the reactlon does not occur,

1

1B9(a) The noble gases have duplet conflguratlon for hellum and octet configurations

for neon, argon, krypton and xenon / All the noble gases have 8 electrons inthe outermost shell except for helium with 2.This makes noble gases unlikely to form ions resulting in a lack of reactivity /Thus noble Bases will not lose or gain electrons easily.

1

1

Beb) Density of xenon = 131 /24 = 5.45 g dm'! ?

A1

c E

D

A

I

5

A2(a) CsHnOs)2CuHsoH+2CO:Glucose in the grape juice undergoes fermentation in the presence of yeast toproduce ethanol resulting ln a drop ln volume ofgrape julce and a rise involume of ethanol.After 30 days, fermentation stops as the concentration ol ethanol kills theveast resulting in a constant volume of ethanol of 1.0 dm}.

7

1

1

A2(b) Volume of ethanol = 1.0 dm3Volume of wine = 5 + 1 = 7 dm3% of ethanol = 1.O / 7 x 7OO% = 74.?96

1

1

42(c)i Purple to colourless 1

A2(c)ii The orldatlon state of manganese decreases in the reaction from +7 in MnOr'to +2 in Mnz', j

lAward 1 m only if at least one of the oxidation states is correctl

1

t

A3(a) Mg (sl + Cu2'(aq) Cu [s) + Mg2'(aq] zA3(b) No. of moles of MS= O.8 I 24 = 0.0333 mol

Concentration of Cu2' = 0.0333 / 0.05 = 0.657 moudmr1

1

A3(c) Plnk / reddish-brown solid is formed.Blue solution decolourises.

1

1

A3(d) Correct shape indicating energy level of products lower than leactantsCorrect labelting of enthalpy change . .

Correct labelling of activation energy[-1 m for wrongly labelled axisl

1

II

A4(a) Water does not conduct electricity as it is a covalent compound.The hydrochloric acid dissolves to form free-moving ions to conduct electricity.

1

IA4(b) Hydrogen gas.

It extlnguishes llghted splint with a'pop'sound,1

1

Aa(c) 4 oH') 2 Hro + or+ 4eThe hydroxide ions are preferentially discharged to form oxygen sas.

1

144(d) 2HrO)2Hz+O:

When water is electrolysed, it produces twice the numbet of moles ofhydrogen as oxygen thus, there is double the volume of hydrogen (gas A)

compared to oxygen (gas B).

1

1

21

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DANYAL EDUCATION

89{c} noble 25 0C 1

8e(d) A krypton atom has a nucleus containing 35 protonl and 48 neutrons.

It has four shells fllled with electrons with the flrst shell havlng 2 electrons,

second shell 8 third shell 18 electrons and

1

1

Be(e) Xenon difluoride exists as discrete covalent

molecules.

/ simple covalent

There are weak forces of attraction between molecules of xenon difluoride'

A small amount of energy ls needed to overcome these weak forces of

attraction.

1

1

1

EitherB10(a) ct

I*c-I

H

HHIIUV

H -C-C-H + Cl-Cl + HllHH

H

H + H-Cl

H

1 mark for correct structural formulae of reactants

1 mark for correct Stluctural formulae of products

mark for condition ,eaction

3

B1o(b) 1

810[c] Hydrogen 1

810(d) Bubble both substances separately into aqueous bromlne.

Vinyl chloride will decolourise reddish brown aqueous bromine while

wltl not decolourlse bromlne-

1

1

810(e) Ag'+ Cl') ABCI

A white precipitate is formed.

The reaction produces insoluble silv", glloride *hich is a wh

1

t1

Or

810(a) 450 "c, 200 atm and lron as catalYst

lAward 2 marks for three correct conditions, 1 mark for two2

B1o(b) H+ + OH- 2

% of tittogen by m ass = 28 I aO =3;-S% -

I

1 mark for correct sharlng of electrons

I mark for correct number of valenfe electrons

)810(d)

810(e) Filter mlxture to Separate calclum carbonate ammonium

nitrate solution as the flltrate.Heat the liltrate until a saturated solutlon and Gool the soluuon for crystals to

form.Fllter the mixture to obtain the crystals as the resldue. wash the crystals with

therna cold distilled

L

1

1

3w!@s

H

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DANYAL EDUCATION