MID.YEAR EXAMINATIONS

1

Name

CHIJ KATONG CONVENT

MID.YEAR EXAMINATIONS 201 8

Secondary Four Express and

Secondary Five Normal (Academic)

sctENcE (cHEMlsTRY, BIOLOGY) 5078/01

Paper 1 Multiple Choice Duration. t hour

Classes: 403, 4O4,405.501 and 502

Additional Materials: Optical Answer Sheets

READ THESE INSTRUCTIONS FIRST

There are forty questions on this paper. Answer all questions. For each question there are four possibleanswers, A, B, C and D.Choose the one you consider correct and record your choice in soft pencil on the separate OpticalAnswer Sheet.Complete the Chemistry and Biology sections on two separate Optical Answer Sheets provided.

Read the instructions on the Optical Answer Sheet very carefully.

Each correct answer will score one mark. A mark will not be deducted for a wrong answerAny rough working should be done in this booklet.

A copy of the Data Sheet is printed on page 16.A copy of the Periodic Table is printed on page 17

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

This oleslion naoer consists of '17 orinted naoes

() Class:

Write in soft pencil.Write your name, registration number and class on all the work you hand in.Do not use staples, paper clips, highlighters, glue or correction fluid/ tape.

2

CHIJ Kalong Convent l\,,lid'Year Exams 2018 Science (Chemistry, Biology) 5078/0'1 Sec 4El5N(A)

1 Diagrams X, Y and Z represent the three states of matter

XY Z

o

Which change occurs during boilang?

XtoYYloZZtoXZloY

P, Q, R and S are pieces of apparatus

P o R

50 cm3 z5 cm"100 cm3 50 cm3

Which row describes the correct apparatus for the measurement made?

apparatus measuremenl madeABcD

P

oR

S

15.60 cm3 of acid to be added to alkali in a titration1 cm3 of acid to be added to calcium carbonate in an experiment

75 cm3 of gas given off in a thermal decomposition reaction20.0 cm3 of alkali to be used in a ti'tration

3 Which method of separation should be used to obtain pure water from coppe(ll) sulfate solution?

A crystallisationB evaporation to drynessC filtrationD simple distillation

ABcD

2

S

oo

4

3

CHIJ Kalong Convent l\rid-Year Exams 2018 Science (Chemistry Bioloqy) 5078/01 Sec 4El5N(A)

A food colouring is compared with four different dyes. The chromatogram produced is shown in thediagram.

Which dyes does the food colouring contain?

A l and 2 onlyB 'l and 3 onlyC 2and 3 onlyD 2and4 only

5 The table shows the boiling points of acetone and water.

substance boiling poinu 'Cacetonewater

56100

A sample of water was found to contain a small amounl of acetone

What could be the boiling point of the water sample?

56 "C78 .C

100 'c104 "C

6 \Mich diagram shows a mixture of two compounds?

ABcD

CL:I

DcBA

t a

a

aa

aa

tfood

colouringdye 1 dye 2 dye 3 dye 4

I

-@() C@

]C.-... Q .-LIEU% .Om

CHIJ Kalong Convent Mid-Year Exams 2018

4

Science (Chemistry, Biology) 5078/01 Sec 4ElsN(A)

7 Which statement about an atom is correct?

A The nucleon number is smaller than the proton number.B The nucleon number is the sum ofthe number of protons and electronsc The number of proton always equals the number of electrons.D The number of proton always equals the number of neutrons.

I How many hydrogen atoms are there in 4 moles of ammonia gas?

A 1.5 xB 1.8 xC 2.4 xO 7.2 x

20 cm340 cm3

60 cm380 cm3

10'3 atoms1024 atoms1024 atoms102a atoms

9 20 cm3 of carbon monoxide was burnt in 40 cm3 of orygen.

The equation of the reaction is shown.

2CO(g)+Oz(g)-,2COz(g)

Vvhat is the total volume of gas remaining at the end of the reaction?

ABcD

10 Due to acid rain, the acidity of the soil is increased, making it unsuitable for plant growth

Which substance is used by farmers to decrease the acidity in the soil?

A calcium carbonateB calcium hydroxideC calcium nitrateD calcium sulfate

11 An unknown oxide was added separately to hydrochloric acid and aqueous sodium hydroxide. The pHof the resulting solution was measured and shown in the table.

chemical pH of resultinq solutionhydrochloric acidsodium hydroxide

7.07.0

What could the unknown oxide be?

A aluminium oxideB carbon monoxideC potassium oxideD sulfur dioxide

CHIJ Katong Convent [/id-Year Exams 2018 Science (Chemistry, Bioloqy) 5078/01 Sec 4El5N(A)

12 The electronic slructures of atoms X and Y are shown.

What is the formula of the covalent compound formed between X and Y?

A XYsB XY:CXYD X:Y

Which statement is correct?

13 The table shows the properties of substances J, K, L and M

Which substances are metals?

A J and KonlyB J and LonlyC Kand MonlyD Land Monly

14 The table shows the electronic configuration of four elements, P, Q, R, S.

element electronic configurationPoR

S

subslance density/ g/dm3 melting poinU 'Celectrical

conductivity insolid state

JKL

M

2.15.7b.J19.3

11523213261 064

poorgoodpoo rqood

A P and R are in the same group.B Q and R have the same number of electron shells.C Q and S are in the same period.D R and S have the same number of valence electrons

2.22.8

2.8.22.8.7

6

CHU Katong Convent Mid-Year Exams 2018 Science (Chemislry, Bioloqy) 5078/01 Sec 4Ei 5N(A)

15 The table shows the results of some halogen displacement experiments

halide solutionhal ogenadded

X Y Z

X

Y

Z

16

Key:

r' visible reaction

x no visible reaction

What row shows the order of halogens in increasing reactivity?

Solid hydrated sodium carbonate was added to aqueous citric acid. The mixture was stirred and thetemperature was recorded every 10 seconds. The results are shown on the graph

15

temperature/'C

'10

5

20

20

00 40 60

time/ s

80 100

Which row describes the reaction?

lowest hjqhestABcD

XYYZ

YXZX

ZZx

I +

reaction type energy changeABcD

neutralisationneutralisationpreciprtationprecipitation

endothermicexothermic

endothermicexothermic

tl

ffi

ttttttl T-L]IIJ TTTIIII TTTT

ffitttltt ITTTTTTTITTl= ITttttl-T-rT-rrTT

TI-I-TTTTTT tlttttlt

tt1t I I I T-TI-T-

ffiffi

7

CHIJ Kalong Convent Mid-Year Exams 2018 Sec 4ElsN(A)

17 Which process is endothermic?

A condensationB freezingC photosynthesisD rusting

18 The effect of temperature on the rate of the reaction between zinc and hydrochloric acid can beinvestrgated by measuring the production of gas.

Which equipment is not required for the investigation?

A condenserB gas syringeC stopwatchD thermometer

19 The element vanadium, V, forms several oxides

Which reaction shows oxidation taking place?

A VOz - VzOr3 \,rrQ5 ---+ VOzC VrO3 ---+ VOD VzO: - VzOs

20 The apparatus shown is set up and left for a week

damp iron wool

atr

water

Which diagram best shows the level of the water at the end of the week?

DCBA

Science (Chemistry, Biology) 5078i01

CHIJ Kalong Convent [,4id-Year Exarfs 20'18

8

Science (Chemistry, Biology) 5078/01 Sec 4ElsN(A)

Data Sheet

Colours of Some Common Metal Hydroxides

calcium hydroxide white

coppe(ll) hydroxide light blue

iron(ll) hyd roxide green

lron(lll) hydroxide red-brown

lead(ll) hydroxide white

whitezinc hydroxide ]

I

Science (Chemistry, Biology) 5078/01 Sec 4E5N(A)

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Name

10

CHIJ KATONG CONVENT

MID.YEAR EXAMINATIONS 201 8

Secondary Four Express and

Secondary Five Normal (Academic)

Class

5078/03

Duration: t hour 15 minutes

FOR EXAMINER'S USE

Paper 1 t20Paper 3

Section A t45t20

TOTAL / 85

sctENcE (cHEMtSTRY)

Paper 3 Chemistry

Classes: 403, 404,405,501 and 502

Candidates answer on the Question Paper.No Additional Materials are required.

READ THESE INSTRUCTIONS FIRST

Section AAnswer all questions.Write your answers in the spaces provided on the Question Paper

Section BAnswer any two questions.Write your answers in the spaces provided on the Question Paper

A copy of the Data Sheet is printed on page 15.A copy of the Periodic Table is printed on page 16

At the end of the examination, hand in:(a) Section A;(b) Section B separately.

INFORMATION FOR CANDIDATESThe number of marks is given in brackets [ ]at the endof each question or part question.

)

Write your name, class and registration number on all the work you hand in.Write in dark blue or black pen on both sides of the paper.You may use a soft pencil for any diagrams or graphs.Do not use staples, paper clips, highlighters, glue or correction fluid/ tape.

Section B

CHIJ Katong Convenl Md-Year Exams 2018

11

Science (Chemlstry) 5078/03 Sec 4El5N(A)

,|

Section A [45 marks]Answer all the questions in the spaces provided

Substances can be classifled as elements, compounds or mixturesComplete Table 1 .1 to describe the following substances.

Table 1.1

substanceclassiflcation

(element, compound or mixture)atoms

found within the substance

hydrogen sulfide compound

brass

limestone compoundl3l

lTotal: 3l

2 lron is the fourth most common element in the Earth's crust and at is also believed to form a largeextent of the Earth's core.

(a) Pure iron can be prepared by the thermal decomposition of iron pentacarbonylFig. 2.1 shows the struclure of iron pentacarbonyl.

o\"

"e"

oIcIlre-c-o'lcIo

Fig. 2.1

Write the chemical formula for iron pentacarbonyl. ... ... . .. ... . .

(b) (i) lron metal oxidises partially to form iron(ll) oxide.

Predict the electrical conductivity of this compound bywhich conductivity is observed or not at all.

t11

including the condition under

t1l

hydrogen, sulfur

CHIJ Katong Convent ldid-Year Exams 2018 Scaence (Chemistry) 5078/03 Sec 4El5N(A)

2 (b) (ii) Complete Table 2.'l to show the number of electrons, neutrons and protons in iron(ll) ionand oxide ion.

Table 2.1

number ofprotons

number ofneutrons

number ofelectrons

23r"'. 26

168 O2-

12)

(c) (i) !f re ano !! re are two common isotopes of iron

Define isoropes.

............ tll

(ii) These iron isotopes have drfferent physical properties but exhibit same chemicalproperties.

Explain this observation.

... . t1]

[Total: 6]

3 \Men a colourless solution of coppe(l) chloride is left in a beaker for a period of time. the followingreaction takes place.

2cuc(aq), CUC/r(aq) + Cu(s)

(a) Calculate the oxidation state of copper in CuC/ and CuC/2.

oxidation state of copper in CUC/

oxidation state of copper in CUC/2

(b) Explain, in terms of change in oxidation states, why CUC/ is both oxidised and reduced in thisreaction.

12)

12

I

l2l

CHIJ Katong Conveol Mid-Yeaa Exams 2018

13

Science (Chemlslry) 5078/03 Sec 4Ei 5N(A)

3 (c) Describe one observation in this reaction

. . I1l

lTotal: 5]

4 lal Name the pieces of apparatus most suitable to complete the following laboratory procedures:

(i) separate a preciprtate from a solution,

. ..t11

(ii) measure exactly 25.30 cm3 of solution inlo a conical flask,

. I1l

(iii) measuring the mass gained in a reaction,

t1l

(iv) bubbling gas into a test-tube containing solution

t1l

(b) Chromatography can be used to separate the coloured pigments extracted from lavenderflowers. The apparatus used is shown Fig.4.1.

After a few minutes, the solvent vapour fills the whole chromatography jar

id

chromatography paper,.

start line solvent

Fig. 4.1

Describe what happens to the movement and arrangement of the solvent particles as theybecome a vapour.

. l2l

ffotal: 6l

L

CHIJ Kalong Convent I\rid-Year Exams 2018

14

Science (Chemislry) 5078/03 Sec 4El5N(A)

5 A solution of nitric acid is prepared by diluting 0.15 mol to make 100 cm3 of solution.

(a) Calculate the concentration of this solution in mol/dm3 and g/dm3.

concentration = mol/dm3 [1]

concentration = g/dm3 [1]

(b) The chemical equation for the reaction between nitric acid and potassium carbonate is asfollows:

2HNO3 + K2CO3 -, 2KNO3 + COz + HzO

100 cm3 of 0.5 mol/dm3 nitric acid is added to an aqueous solution containing 0.02 mol ofpotassium carbonate.

(i) Calculate the number of moles of nitric acid.

number of moles =

(ii) State the limiting reactant in this reaction.

t1l

. t1l

(iii) Calculate the number of moles of potassium nitrate formed.

... ... . t11

lTotal: 5l

number of moles =

CHIJ Kalong Convent Mrd-Year Exams 2018

15

Science (Chemistry) 5078/03 Sec 4El5N(A)

6 Fig. 6.'l describes some of the properties and reactions of several substances.

neutralise withsolution Q

add aqueoussodium hydroxide

add dilute nitricacid and aqueous

silver nitrate

Fig. 6.1

(a) ldentify P, Q, R and S.

P

o

R

s

(b) Wrate the ionic equation for the reaction of R with aqueous silver nilrate.

t4l

t1l

lTotal: 5l

Pblack solid

Rblue aqueous

solulion

white precipitateSblue precipitate

CHIJ Katong Convenl M d-Year Exams 2018

16

Science (Chemistry) 5078/03 Sec 4EisN(A)

7 (a) Lithium, sodium and potassium belong to Group I of the Periodic Table.Table 7 .1 shows the observataons when these three metals react with water

Table 7.1

Group I metal observationlithium reacts quicklysodium reacts violently

potassiu m reacts very violentlv

(i) Describe and explain the reactivity of Group I metals down the group

l3l

(ii) Rubidium is located below potassium in Group l.

Predict what would happen when rubidium reacts with water

111

(iii) Name the gas evolved when Group I metals react with water

. t1l

(b) Group 0 elements are also known as noble gases.

(i) State one physical property of noble gases.

(ii) Using your knowledge of electronic structures, explain why elements in Group 0 areunreactive.

t1l

[Total: 7]

17

CHIJ Kalong Convent I\rid-Year Exams 2018 Science (Chemistry) 5078/03 Sec 4El5N(A)

I The petrol burnt in car engines react with air to form a mixture of gases.Table 8.1 shows the composition of the mixture of all the gases coming from car exhaust fumes.

Table 8.'l

gas % of gas in the exhaust fumes

carbon dioxide 15

carbon monoxide 3

hydrocarbons 2

hydrogen 1

oxides of nitrogen 1

oxygen 1

water vapour 18

gas W 59

(a) ldentify gas W. t1l

(b) The amount of carbon dioxide emitted by vehicles contributes to the increasing concentrationof the gas in the atmosphere.

Explain why this is a global concern.

12)

(c) Explain why carbon monoxide is found in the exhaust gases.

. t1l


18


8 (d) Water is one of the major by-products in the combustion of petrol in vehicles.

Draw a 'dot and cross' diagram of water, showing only the arrangement of electrons on thevalence shells.

l2l(e) The combustion of petrol is exothermic.

(i) Define exothermic.

Ill

(ii) Give another example of an exothermic reaction

t1l

lTotaL 8l

CHIJ Kalong Convent [4id-Year Exams 20'18

19

Science(Chemistry) 5078/03 Sec 4ElsN(A)

Name Class

9

Section B [20 markslAnswer any two questions in this section.

Write your answers in the spaces provided.

Magnesium sulfate is formed from the reaction between a metal, M and an acid, N.

(a) Name M and N.

M

N

(b) Write the balanced chemical equation for the reaction between M and N

(c) Describe how pure crystals of magnesium sulfate can be prepared using metal M and acid N.

(d) Magnesium sulfate can also be prepared using acid N and another substance

Name this substance.

12)

t1l

14)

t1l

)

CHIJ Katong Convenl Mid-Year Exams 2018

20


9 (e) The labels on two bottles. one containing acid N and the other containing aqueous ammonia, weremissing.

(i) Briefly describe a method you would use to distinguish between the two solutrons.

t1I

(ii) Stale the result you would expect for acid N using the method described in (e)(i)

.....tl t

lTotal: 101

10 lron is a metal that is commonly used in the conslruction of ships and bridges

(a) lron is extracted from haematite using carbon in a blast furnace. lmpurities from the iron areremoved uslng limestone.

Describe how limestone is used to remove impurities from iron and include suitable chemicalequations in your answer.

t41

(b) When iron is exposed to the environment for some time, it starts to rust

(i) Bridges made of iron are painted to prevent rusting.

Explain how the layer of paint prevents iron from rusting.

l1l

21

CHIJ Kalonq Convent Mid-Year Exalns 2018 Science (Chemrstry) 5078/03 Sec 4E15N(A)

'10 (b) (ii) Some ships that are made of iron prevent rusting by attaching blocks of zinc to its surface.After some time. it was observed the block ofzinc corroded instead of iron.

Explain how attaching blocks of zinc help to prevent the ship from rusting.

t1l

(iii) Predict what happens when blocks of silver metal are attached to the iron surface of the shipinstead of zinc.

t1l

(iv) lt was observed that ships in the sea tend to corrode more quickly than bridges.

Suggest a reason to explain this phenomenon.

... t1 l

(c) ln addition to the production of iron using the blast furnace, iron is also obtained through recycling.

Give two reasons why it is important to recycle metal.

1

2

..121

lTotal: 10]

22

CHl,l Kalong Convent l\,4]d-Year Exams 2018 Science (Chemistry) 5078/03 Sec 4El5N(A)

11 Egg shells are made up mainly of calcium carbonate. A pupil carried out an experiment to react eggshells with excess dilute hydrochloric acid. The gas that was produced was measured at a regular timeinterval to investigate the speed of the reaction.

(a) Predict the solubility of this gas in water

t1l

(b) Complete the diagram in Fig. 11.1 to show the apparatus which could be used to measure thevolume of gas produced.

dilute hydrochloric acid

egg shell

Fig. 11.1

(c) The results of this experiment are shown in Table 1 1 .1

Table 11. t

12)

time/ s 20 40 60 140 180 200 220volume of gas/ cm3 0 14 25 48 50 50 50

Plot the results on Fig. 1 1.2 and draw a smooth curve through the points

volumel cm3

time/ s

100 120 140 160 180 200 220 240

Fig 11.2

(i)

60

50

40

30

20

10

I

{,,

. . . ,.i . .II

iJ

i'' I

I i'I

020406080

0

,l

-''i.

0

l2l

23

CHIJ Katong Convenl Mid-Yea. Exams 2018 Science(Chemistry) 5078/03 Sec 4El5NiA)

11 (c) (ii) Explain why no further measurements were taken aftet 220 seconds.

t11

(iii) Using the graph drawn in (cxi), estimate the volume of gas evolved for the first 100 seconds.

l1l

(iv) Calculate the average speed of reaction in cm3/ s for the first 10 seconds of the reaction.final volume - initial volume{AVeraOeSDeeO=-)' clLrration concemed

cm3/ s [2]

(v) The experiment is repeated with crushed egg shell.On the same axes in Fig. 'l 1 .2, draw the graph you would expect for the second experiment.Labelled the graph as'Q'. t1l

lTotal: 101

CHIJ Kalong Convent Mid-Year Exams 2018 Science (Chemistry) 5078/03 Sec 4El5N(A)

Data Sheet

Colours of Some Common Metal Hydroxides

calcium hydroxide white

coppe(ll) hydroxide light blue

iron(ll) hydroxide green

iron(lll) hydroxide red-brown

lead(ll) hydroxide white

zinc hydroxide white

The Periodic Table of ElementsGroup

I 01

H

I3

Li4

Be5B

11

6c

7N

'14

E

o10

IF

197 I11

Na12

Mg

24

AI

27

14

Si

28

15P

31

't6

S ct

35.5

proton (abmc) nurberatomic symbol

relalive atomic mass

2

He

4

10

Ne

n18

Ar

4019

K

39

2A

Ca

40

Sc

45

Ti

4E

n

5'l

24Cr

52

Mn Fe

56

27Co Ni Cu

64

30Zn

31

Ga9.llwn

70 73

AS

u

79

Br

80

36Kr

8437

Rb

85

3E

ST

8B 8S

40Zt

s1

4',1

Nb

93

42t\.40

96

43Tc

44Ru

101

45Rh

103

46Pd

106

47Ag

108

48ft11?

49ln

115

50Sn

1't9

51

Sb

122

52Te

18

53t

127

54Xe

131

55Cs

56Ba

137

l-tf

178

Ta

181

74

184

75Re

186

76Os

190

77k

78Pt

lold

80Hg

241

81

TI

n4

Pb

207

Bi

209

84Po

85 88Rn

a7Fr

"T'88Ra

89 - 103 104

Rf105Db,1r,

106SS

107Bh

"Y*

108Hs

1@Mt

110US

d.ms!adi!m

111Rg

't12Cn

114FI

116

lanthanoids

actinoids

La

r3s

58Ce

140

5S

Pr

14t

60Nd

144

Pm Sm

150

63Eu

152

64Gd

157

65Tb

159

mDy

163

67Ho

165

68Er

69Tm

160

70Yb

173

71

Lu

17580Ac

s0Th

91

Pa

231

92U

93Np

s4Pu Am

96Cm

97BK

98 100

Fm101

Md102No

103Lr

N

oIC

d

m

l

q.

o

l.a

z

The volurne of one nnle of any gas ls 24 dm3 at room temperature and pressure (r.t.p.).

CHU Kgpng Convent

4E/5N Science Chemistry Mid-Year Exam Z)18

Answer scheme

1 2 4 5 6 8 I 10

B A D c D D c D c B

11 12 IJ 14 15 16 17 '18 to 20A D c A B A c A D B

Paper 3

Sectron A

Qn Answe rs

1

ox en

dro en, sjlfurm tliEilrf,aE

compound

substance

calcium, carbon,co zincmixture

or mixturecompou

limestone

brass

atornsfound within the

substance

classification(elemqrt, compound

Fe(CO)s

2b(il lron(ll) oxide conducts electricity only in molten formORlron(ll) oxide does not colducts electricity as a solid )

2b(ii)number of

protonsnumber ofelectrons

29 Fc2+ lo 30 24

L6n2- I 10

2c(i) lsotopes are ators of the same element with the same number of orotons budifferent number of neutrons

t

2c(ii)

3a oxidation state of copper in CUC/oxidation state of copper in CUC/:

3b OrC/ is oxidised to CUC/2 as the oxidation state of Cu increases from +1 in CuCJto +2tn CuC/:.

CUC/ is reduced to Cu as the oxidation state of Cu decreases from + 1 in OIC/ to 0 inGl.

II+@LIETCTE

Paper 1

number ofnetJtron s

As the isotopes have the same number ofvalence electrons, the!, possess the samechemical properties.

=+1=+2

3c The colourless solution tums blue 28

ORA pink/ browni reddish+ro,vn solid is formed

4a(i) ilter tunnel

4a(ii) burette

4a(iii) electronic balance

4a(iv) delivery tube/ teat pipette

4b \Men the solvenl partides become a vapour, they aremovjng at hioh soeeds in all direcions andspaced Ig[ apart.

5a Concentration of HNO: in mol/dm3 = 6.15 * ,1'0,1 = 1.5 mol/drn^IOOO

-

con centratlon of HNo: in g/dm3 = 1.5x63=$!!g@a

5bi Numberof moles of HNO: = 9x I 5 = 0.05 molII]L'U

Mole ratioK:COs:KNO:=1:2

Numberof moles of KNO3 = 0.02x2= 0.04mol

5bir

5biii

6a P: copper(ll) oxide / CUOQ: hydrochloric acid / HC/R: coppe(ll) chloride / CUC/2S. copper(ll) hydroxide / Cu(OH):

6b Ag. (aq) + C/ (aq) + 4961 1s;

7ai The reactivity of Group I metals increases down the group

Down the group, there are @.M.gl3|E@relIS between the nucleus and hevalence electron.

Hence, there is a @to attain the noblegas eleclronic confi guration.

Tait

Taiii Hydrogen gas

7bi Noble gases arel have. coicurless. odourless. gases at rodn temperature and pressure OR have low mdting and boiling points. insduble in water. poor conductors of electridty. low densities

(any one)

Potassium carbonate I K2CO3

It reacts explosively

Tbii They have@and already achia/ed a stable noblegas electronic configuratron.

8a nifogen/ N2

8b Carbon dioxide is a greanhouse gas / causes dimate change / causes globalwarming.

This results in ice caps melting (or rise in sea ls/els) / increased flooding idesertification / increased death of corals.

It is formed due to incomplete combustion

Bd

Keya : electron from O

X :electron fro

oel A reaction/ a change in which heat is given oul to the surroundings

Seii Rusting, respiration. neutmlisation or any acceptable an$/er

Section B

Qn

9a M. magnesiumN: srlfunc acid

9b Mg+HzSOq)MgSOa+Hz

9c Steps for making crystals:1 . Add g@ magnesrum metal to a test tube coltaining sulfuric acid and stir.

2. Filter to obtain the filtrate, which is magnesum sulfate solution, and rernove theexcess magnesium metal residue.

3. Heat he filtrate till it is saturated.4. Alloru the safurated solutim to 949[ so that the salt can crystallise

5. Filter to collect the crystals. Wash the crystals with a litte cold distilled water torernove impurities and dry between sheets of f lter paper.

9d Niagnesium oxide / magensium carbmate/ magnesium hydroxide

9ei Add a few drops of universal indicator solution into each solution, OR

Dip a piece of red and blue lifnus paper into eacfr sdution.

9eii The solution will furn from green to red. OR

er will turn redThe red litmus a r will remain red and the blue lifnus10a rst decomoosed by heat to produce carbon dioxide and caloum

oxide.CaCO: (s) -r CaO (s) + CO: (g)

Limestone is fi

Answers

Calcium oxide reacts with the impqdties from iron, which is sand, to form @!!g!descao (s) + sio2 (s) r caSios (/)

1obi Paint serves as a protective layer that prevents iron from coming into contact withwater and oxvqen.

10bii Zinc is more reaclive than iron,henc€ zinc will react with water and oxygen first.

1obiii The ship will rust

'10biv

10c / Rerycling helps to conserve f nite/ non-renewable metal ores./ Recycling helps to save energy, hence less fossil fuels are bumt for energy

produclion./ Recycling helps to save cost of extracting metals./ Recycling reduces pollution as rerycling metals creates less pollutants than

extracting metals frorn its ores./ Recycling reduces the need of landfills for metal extraction wastes

(any two)

11a The gas (carbon dioxide) is slightly soluble/ insoluble in water

'1 1b a labelled gas syringe

dilute hydrochloric acidgas synnge

egg shells

1 1c(i)

d

I

1

,olur0d crnr

]it'.

I

c

al

o :,1 4!' e0 B0 100 !20 140 l8O 14, 2m 2A 2{O h.r 3

.,

--:1,'...

1 1c(il) AII the egg sfrell (calcium carbonate) had been used up

11c(iii) Based on sfudents graph,Acceptable range of 41 - 4.3 cm3

The presence of sodium chlonde in seawater results in the increase of the speed olru sting.

11qiv)

11qv) a graph with a higher gradient but same fnal volume

average speed =oolutle at LO sec - polunV at 0 sec

10 s€c

31onBased gmph

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MID.YEAR EXAMINATIONS