SPM Che2 Q&A (Kedah)

8/14/2019 SPM Che2 Q&A (Kedah)

1/28

2k

MOZ@C

SMS MUZAFFAR SYAH , MELAKA


2/28

2k

MOZ@C



3/28

2k

MOZ@C



4/28

2k

MOZ@C



5/28

2k

MOZ@C



6/28

2k

MOZ@C



7/28

2k

MOZ@C



8/28

2k

MOZ@C



9/28

2k

MOZ@C



10/28

2k

MOZ@C



11/28

2k

MOZ@C



12/28

2k

MOZ@C



13/28

2k

MOZ@C



14/28

2k

MOZ@C



15/28

2k

MOZ@C



16/28

2k

MOZ@C



17/28

2k

MOZ@C



18/28

2k

MOZ@C



19/28

2k

MOZ@C



20/28

PEPERIKSAAN PERCUBAAN SPM 2008

NEGERI KEDAH DARUL AMAN

MARKING SCHEME

CHEMISTRY PAPER 2

Section A

(a) An acid that dissociates/ ionises completely in water

to form a high concentration of hydrogen ions

1

1

(b) pipette 1

(c) From pink to colourless 1

(d) (i) HCl + NaOH NaCl + H2O 1

(ii) 0.1 x 20 = 1

Mb x 25 1

25 Mb = 2Mb = 0.08 mol dm

-3

1

1

(e) (i) 10 cm3

// half the volume of hydrochloric acid 1

(ii) Sulphuric acid is a diprotic acid whereas hydrochloric acid is a

monoprotic acid.So, the sulphuric acid used has twice the number of hydrogen ions

compared to hydrochloric acid .

1

1

1.

Total 10

(a) (i) Zinc

hydrochloric acid / suphuric acid

1

1

(ii) Zn + 2HCl ZnCl2 + H2 1

(b) (i)

Empirical formula is MO2

1

1

1

(ii) MO2 + 2H2 M + 2H2O 1

( c) The air in the combustion tube must be displaced before lighting the

hydrogen gas// The heating, cooling and weighing is repeated until aconstant mass is obtained

1

(d) No.Magnesium is more reactive than hydrogen.

11

2.

Total 10

j2kMOZ@C



21/28

(a) Propene

Vinyl chloride // Chloroethene

1

1

Advantage: Light // Cheap // convenient 1(b)

Disadvantage: Non-biodegradable // produces toxic gas when burnt 1

(c) i Increase hardness // reduce corrosion / rusting // improve theappearance//to make it more attractive 1

ii To make Medals // swords // statues // bells 1

iii 1

iv Atoms/particles in copper are arranged in an orderly manner in layers.

The presence of tin atoms disturbs the orderly arrangement of copperatoms.

This will make it difficult for the layers of tin atoms to slide on eachother.

1

1

1

3

Total 10

Tin

Copper

(a)

1

(b) i Isotopes are atoms (of the same element) with the same number ofprotons/proton number but different number of neutrons/nucleon

number. 1

ii Any example of isotope

Sample answer; carbon-14,cobalt-60, sodium-24 etc

1

(c) i 12 1

iiY

1

4

(d) i Liquid 1

X

23

11

j2kMOZ@C



22/28

(ii)

1

iii Becomes faster/ more active 1

iv correct curve

boiling point

1

1

Total 10

(a)

The stopper is drawn in the correct position(half in, half out)refer the diagram

1

(b) 2HCl + CaCO3 CaCl2 + H2O + CO2 1

5

(c) 32 cm3

50 s= 0.64 cm3s-1

1

(d) (i) Both axes are labelled with the correct units

scales are suitable(cover graph paper)

All points are transferred correctlySmooth curve

1

1

11

(ii) A tangent is drawn on the graph

Calculation0.246 cm3s-1 + 0.024 // range [0.222 - 0.270]

1

11

Total 10

Time / min

Temperature /oC

65

j2kMOZ@C



23/28

6 (a) Hydrogenation// addition (of hydrogen) 1

(b) (i) Phosphoric acid // H3PO4 1

(ii) C2H4 + H2O C2H5OH 1

(iii) Fermentation 1

(c) (i) Ethanoic acid 1

(ii) Acidified potassium dichromate(VI) solution // Acidified potassiummanganate(VII) solution

1

(d) C2H5OH C2H4 + H2O 1

(e) (i) Esterification 1

(ii) - has a sweet smell// fruity smell

- a neutral compound

- colourless liquid- slightly soluble in water

- readily soluble in organic compounds[ Choose any one ]

1

(iii)H O H H

H C C O C C H

H H H

1

Total 10

j2kMOZ@C



24/28

Section B

Hydrogen(gas) 1(a)

2H+(aq) + 2e H2(g) 1 2

(b) Properties Cell A Cell B

1. Type of cell Voltaic cell Electrolytic cell

2. Energy change Chemical

electrical Electrical

chemical3. Electrodes Positive terminal:Copper

Negative terminal:

Magnesium

Anode: CopperCathode: Copper

4. Ions in electrolyte Cu2+

, SO42-

, H+

and OH-

ionsCu

2+, SO4

2-, H

+and OH

-

ions

Positive terminal:Cu2+ + 2e Cu

Anode:Cu Cu2+ + 2e

5. Half equation

Negative terminal

MgMg2+

+ 2e

Cathode:

Cu2+

+ 2e Cu

Positive terminal:

Copper plate becomes

thicker

Anode:

Copper

dissolves//becomethinner

6. Observation

Magnesium becomesthinner/dissolve

Cathode:Copper becomes thicker

11

1

1

1

1

1

1 8

(c) (i) Improve the appearance//to make it more attractive

To prevent/ reduce corrosion/ rusting

1

1 2

(ii) Procedure:1. Iron ring is then connected to the negative plate on the battery

while the silver plate is connected to the positive terminal of the

battery//Iron ring is made as cathode while silver plate is madeas anode

2. Both plates are immersed into the silver nitrate solution.

3. The circuit is completed

Functio

nal apparatus set-up

Label correctly:silver plateSilver nitrate solution

Iron ring

Cathode: Ag+

+ e Ag

Observation: Grey /silvery solid is depositedAnode : Ag Ag+ + eObservation: Anode/silver become thinner//dissolve

1

11

1

1

1

1

1

1

max

8/9

7

Total 20

j2kMOZ@C



25/28

(i) Atom R is located in Group 17, Period 3 1

1

8 (a)

(ii) Electron arrangement of atom R is 2.8.7.It is located in Group 17 because it has seven valence

electron.It is in Period 3 because it has three shells filled with

electron

1

11 5

(b) (i) Atoms P and R form covalent bond.

To achieve the stable electron arrangement,atom P needs 4 electrons while atom R needs one electron.

Thus, atom P shares 4 pairs of electrons with 4 atoms of

R,forming a molecule with the formula PR4 // diagram

1

11

1

1

(ii) Atom Q and atom R form ionic bond.

Atom Q has the electron arrangement 2.8.1. and atom Rhas the electron arrangement 2.8.7.

To achieve a stable (octet )electron arrangement,atom Q donates 1 electron to form a positive ion//equation

Q Q+ + e

Atom R receives an electron to form ion R-//equation and

achieve a stable octet electron arrangement.

R + e R-

Ion Q+

and ion R-

are pulled together by the strongelectrostatic forces to form a compound with the formula

QR// diagram

1

1

1

1

1

1

11

RR

R

R

+

j2kMOZ@C



26/28

(c) The ionic compound/ (b)(ii) dissolves in water

while the covalent compound / (b)(i)does not dissolve in water.Water is a polar solvent that can cause the ionic compound todissociate into ions.

Covalent compounds are non-polar and can only dissolve in

organic solvents.

OR

The melting point of the ionic compound/ (b)(ii) is higher than

that of the covalent compound/ (b)(i) .

This is because in ionic compounds ions are held by strongelectrostatic forces.

High energy is needed to overcome these forces.In covalent compounds, molecules are held by weak

intermolecular forces.

Only a little energy is required to overcome the attractive forces.

OR

The ionic compound/(b)(ii) conducts electricity in the molten or

aqueous statewhereas the covalent compound/(b)(i) does not conduct

electricity.

This is because in the molten or aqueous state, ionic compoundsconsist of freely moving ions.

Covalent compounds are made up of molecules only

11

1

1

1

1

1

1

1

1

1

1

1

4

max

4/5

4

Total 20

9 (a) (i) Based on the equation, iron(II) ion is oxidised toiron(III) ion

So, iron(II) ion acts as a reducing agent

1

1

(ii) Based on the equation, iron(II) ion is reduced to

ironSo, iron(II) ion acts as an oxidising agent

1

1 4

(b) eMgMg 22

Oxidation number of magnesium increases from 0 to +2, So

magnesium undergoes oxidation

CueCu 22

oxidation number of copper decreases from +2 to 0, so copper(II)ion undergoes reduction

1

1

1

1 4

(c) (i) Reduction is a reaction that involves gain of electron.

Oxidation is a reaction that involves loss of electron.

1

1 2

j2kMOZ@C



27/28

(ii) At the negative terminal:

Iron(II) ion releases one / loses one electron andis oxidised to iron(III) ion.Fe2+ Fe3+ + e

The green coloured solution of iron(II) sulphate turns brown.

The electron flows from the negative terminal// carbon

immersed in iron(II) sulphate solution to the positiveterminal// carbon immersed in bromine water.

At the positive terminal:

Bromine accepts electron andis reduced to bromide ions, Br-

Br2 + 2e 2Br-

The brown coloured bromine water turns colourless.

The deflection of the galvanometer needle shows that there is

a flow of current

1

11

1

1

11

11

1 10

Total 20

10 (a) Exothermic reaction is a reaction that releases heat to thesurrounding

The energy content of the products is lower than the energy

content of the reactantsEndothermic reaction is a reaction that absorbs heat from the

surroundingThe energy content of the products is higher than the energy

content of the reactants

1

1

1

1 4

(b) A reacts with B to form C and D

A and B are the reactants while C and D are the productsHeat energy is released //The reaction is exothermic

Total energy content of A and B/reactants is higher than totalenergy content of C and D/products

1

11

1 4

(c)

Copper container

thermometer

water

Spirit lamp+

ethanol

j2kMOZ@C



28/28

250 cm3

of water is measured using a measuring cylinder and is

then poured into a copper container.The copper container is placed on a tripod stand.The initial temperature of the water is measured and recorded.

A spirit lamp containing ethanol is weighed and recorded.

The spirit lamp is placed directly below the copper container(as

in the diagram.)The wick of the spirit lamp is lighted.

The water is stirred using a thermometer.When the increase in water temperature is 30 oC, the flame is put

off and the highest temperature reached is recorded.

The spirit lamp is weighed again.Results:

Initial temperature of water = t1oC

Highest temperature of water = t2oC

Rise in temperature = (t2 - t1)oC = T oC

Mass of lamp + ethanol before combustion = m1 g

Mass of lamp + ethanol after combustion = m2 g

Mass of ethanol burnt = (m2 m1) g

Number of mol of ethanol = (m2 m1) = n

46

Heat change = 250 x 4.2 x T= q J

Heat of combustion = - q kJ mol-1

n x 1000

1

11

1

1

1

11

1

1

1

1

1

1

Max

12/14

Total 20

j2kMOZ@C

SPM Che2 Q&A (Kedah)

Documents

Transcript of SPM Che2 Q&A (Kedah)