8/9/2019 Ce Chem07 Ms

1/8

2.

(a)

Cr-aa

Y'' t

/

(b) (D

The

products

of crackingcontained nsaturated

h:rdrocarbons)

alkenes

C=C'/ ethene/

reasonablb ame

of alkene

carbon-carbon

oublebond

must

be shown f usingmolecular

formulal which decolourisedhe brominewater mmediately

by addition eaction.

C2

's

a

(ii)

The

products

of cracking also contained aturated

hydrocarbons)

alkanes methane/

reasonable

ameor

molecular

ormulaof alkane

do

not

acceptC-C] which decolourised

the

brominewater slowly by substitutioneaction.

i l . , ' l

/ t

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colourless)

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+

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or

Cl2

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zKl

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lz

(ii)

Noobservablechange/reaction

o'/,

h,,4-&

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asterl

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4.

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Both

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wine

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$ot69ut:sa-

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electricitY.

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-Hz

(c)

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irectly

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iving out

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5, (a )

(b)

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Z

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mpurit ies]

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be

oxidized

/

become

co

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/ copper

reacts

with

o

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(or

air)

(e)

Percentage

f

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mass

n

the

sample

(2.00 1.75)

2,00

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FORTEACHERS'SEONLY

MgO+Clz+C-*

MgClr+CO

or 2MgO

+ZClz+C

-ZMEClz+COz

t

redox

reacti

n)

t

displacement

reaction)

Potassium

s a

more

powerful

educing

gent

more

eactive

han

magnesium.

(c) (i) electrolysis

(ii)

Magnesium

chloride

s an

electricity

in

molten

state/

contains

obile ons.

(d)

sacrificial

rotection

making

alloy firework

flash

do

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pplication

f MgO]

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odium ydroxide olution

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4/8

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5/8

RTF'Hilaffi

FOR

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9.

Chemicallkowledge

6

marks)

Corrosive

rooerly

o

safety

glasses

goggles

rubber

gloves

protective

lothings avoid

contactwith skin

or eyes I

wash

with

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ith

skin

o

because

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r

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ut

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f metal

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do-'notmix with

chlorine

I

bleach

r caustic oda

do not

put

n

warm

place

o

because

ill

damage

metal

container

damage

marble toxic

gas

evolvesf mix

with chlorine

I

blpach large

amount

of heat

eleases

f mix with caustic oda/

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gas

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x

(

tt

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t

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f

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8/9/2019 Ce Chem07 Ms

7/8

RrF+f

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FOR

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t2.

(a)

Molerat ioofC:H:O

0.401

0.069

0.531

=-r- t-

12

I

16

(step-mark)

FOR

TEACHERS'

:g/

3>

x

dr(

l*

=

0.033

0.068

0.033

-l :Z:

I

Ernpirical

ormula

of

Z:

CH2O

(b)

Let

he

molecular

ormula

of

Zbe

(CH2O)"

formula

mass

of Z

=

-*;-

x24

=60

(step-mark)

(400

1000)

--

\---r

---E'r/'

(12+2+16)n=60

n

(, : ,03)):o.ct66

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n:2

a\ :_. ,

\1

X.

Molecular

ormula

of

ZisC2HaO2

W#4t

t.

q,,ttt->T

(c)

(i)

HCoOcH3

Explanations:

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[Ja

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8/9/2019 Ce Chem07 Ms

8/8

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\

RTF?,f-HFaffi

FOR

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13.

Chemical

nowledge

6

marks)

The

ollowing5

points.

mark or

each

oint

.;:''.'"

'

1'-n''

"(

nve ionic

group

headand ong hydrocarbon

hain tail.

ravehydrophilic

property

andhydrophobic

roperty.

ls, while soapless etergents

ade rom

petroleurn.

g:

I

,

while

soapless

etergents

ave

SOr-

/

-OSO3-

group.

ardrvater acidic

medium,while soapless

etergents

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Effective

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t-

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il

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e

Both soapyand

soapless etergents

ct aswctting

agents.

r

Both

soapyand

soapless etergents

ct asemulsi&ing

agents.

o

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detergents reusually

biodegradable, hile soapless etergents sually

arenot.

o

Soapless

etergents

anbe ailor-made,

while

soapydetergents

annot.

(6)

( i i)

(i)

The

mark for effective

communication hould elate o the

candidate's

nowledge

n

chemistry.

A candidate

who wrote a

paragraph

hich

s

totally unrelated

o the

question

should

eserve eromarks oth

n chemical nowledge

nd

n effective

ommunication.

The table

below illustrates he

relationship etween

he mark

for chemical

knowledge

and the maximum

mark for effectivecommunication,ogetherwith

the

points

o be

considered

n marking ffective

ommunication.

(iiD

The hreemarks

or effective

ommunicationre

awarded s

ollows

(A)

the ability

to

present

deas n

a

precise

manner,

ncluding he

proper

use of

chemical

erms

(this

mark

shouldnot

be awarded

o answers

hich

contained

a lot

of incorrecVsuperfluous

aterials);

(c)

the ability

to

present

deas

n

a systematic

manner

follow);

the ability

to

present

answer in

para9raph

orm and

sentences.

(i.e.,

he

answer s

easy

o

I

to express

deasusing

full

I

-r

/+

( . ,

Y.

r{

K"

P;-

i v ' -

\.

.

"a

/. J

2007-cE-cHEM-10

mark or chemical

knowledge

maximum mark

for effective

communication

points

o

be

considered

n

paragraph

(iii)

below

4 or

above

3

(A),

(B)

and

c)

3 or

below

2

(B)

and

c)

RTF+Y,HFAffi

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