chem answer paper 2 final

8/8/2019 Chem Answer Paper 2 Final

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SULIT 4541/2 (PP)

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4541/2 (PP) 2010 Hak Cipta JKD Kimia Daerah Kluang SULIT

2

Section A

Q no. Explanation MarksTotal

Mark

1 (a) (i) Magnesium / Mg 1 1(ii) Chlorine / Cl2 // Naphthalene / C10H8 1 1

(iii) Potassium iodide / KI 1 1

(b) (i) solid 1 1

(ii)

At least the particles are drawn in 3 columns and 3 rows in a

closely packed arrangement with identical sizes. 1 1

(c) Magnesium / Mg 1 1

(d) (i) T1oC / T1 1 1

(ii) The heat lost to the surroundings is equal to / (is balanced

by) the heat released .. during the formation of the force of attraction between

particles

1

1 2

(iii) The speed of the particles movement is decreasing //

Movement of particles becomes slower.1 1

Total 10

2. (a) A (chemical) formula that shows the simplest (whole no.)

ratio of each atoms of the element in a compound. 1 1

(b) (i) Number of moles of atoms /mol / mole 1 1

(c) (i) Method II 1 1

(ii) Copper is a less reactive metal (than hydrogen) // Copper is

positioned lower than hydrogen in reactivity series

1 1

(iii) To allow air/oxygen to enter the crucible // to let magnesiumburns / reacts with oxygen completely) 1 1

(d) (i) 33.31 32.29 g // 1.02 g 1 1

(ii) [1.02 / 24] mol // 0.0425 mol 1 1

(iii) 33.99 33.31 g // 0.68 g 1 1

(iv) [0.68 / 16] mol // 0.0425 mol 1 1

(v) MgO 1 1

Total 10


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Mark

3. (a) Group 1 / alkali metals 1 1

(b) 2.8.8.1 / 2,8,8,1 r : 2:8:8:1 1 1

(c) 1. Potassium atom has more number of shells // potassium

atom has bigger size than sodium atom // attractive forces

between nucleus of potassium atom and valence electronsare weaker.

2. Potassium atom can loss / release electron easier.

adp for the word atom

1

1 2

(d) (i) 2Na + Cl2 2 NaCl

Correct formulae of reactants and product

Balance equation

1

1 2

(ii) Ionic bond 1 1

(iii)

- enough no. of shells & electrons for both of ions

- correct charges and labels of ions

1

1 2

Total9

NaCl

+ -


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Mark

4. (a) Cell X : Electrolytic cell / Electrolysis cell

Cell Y : Daniell cell / Voltaic cell / Chemical cell

1

1 2

(b) Cu2+, SO42-, H+, OH- //or names of the ionsAll ions must be stated 1 1

(c)(i) Remains unchanged / not change 1 1

(ii) Cu2+ + 2e Cu 1 1

(iii) Types of electrode / use active electrode 1 1

(d) (i) Chemical to electrical 1 1

(ii) Becomes thinner / (zinc plate) dissolved 1 1

(iii) Greater (voltmeter) reading (obtained).

r : Increase

1 1

(e) [draw an arrow from S to P trough the external circuit]

1 1

Total 10

P Q R S

Cell X

A

Cell Y


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Mark

5. (a)(i)Titration Set 1 2 3

Final reading of

burette/ cm3

12.55 25.05 37.50

Initial reading of

burette/ cm3

0.00 12.55 25.05

Volume of

sulphuric acid

used/ cm3

12.55 12.50 12.45

All of the volume values must be stated in two decimal places

1 1

(ii) The average volume of sulphuric acid

= 12.55 + 12.50 + 12.45

3= 12.50 cm

311 2

(b) (The moment) when the colour of phenolphthalein / solution

change from pink to colourless 1 1

(c) Sulphuric acid completely ionizes / dissociates in water //

degree of ionization is 1 // sulphuric acid produces high

concentration of hydrogen ion in water //

Ethanoic acid partially ionizes in water // degree of

ionization is less than 1

1 1

(d) H2SO4 + 2 KOH K2 SO4 + 2 H2OCorrect formulae of reactants and products

Balance equation1

1 2

(e)(i) Number of mole sulphuric acid = (M x V)

= 1.0 moldm-3

x 12.50 cm3

1000 cm3dm

-3//

= 0.0125 mol

1 1

(ii) From the equation,

1 mole of sulphuric acid 2 moles of water

0.0125 mole of sulphuric acid 2 x 0.0125 mole

1Number of moles of water produced = 0.025 mole

0.025 mol KOH = MB x 25.001000

Concentration of KOH , MB = 1.0 mol dm-3

OR, use MAVA / MBVB = a/b

1

1 2


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Mark

(f) Sulphuric acid is a diprotic acid, for every molecule of sulphuricacid two H

+ions will be produced when added with water. //

Nitric acid is a monoprotic acid,for every molecule of

nitric

acid one H+

ion will be produced when added with water.

1 1

Total 11

6. (a) (i) X : Copper(II) carbonateY : Sulphuric acid (solution)

11 2

(ii)

Salt crystal

[ Functional diagram]- Filter paper must be seen clearly

[Label]

1

1 2

(b) (i) 1. Blue solution is formed

2. Copper(II) carbonate dissolves

3. The effervescence occurred

Any two observation

1

1

2

(ii) To ensure all sulphuric acid react completely.r : acid finished react 1 1

(iii) Crystal / salt is formed 1 1

(iv) Carbon dioxide gas

r : CO2

1 1

(c) Neutralisation

a: reaction between acid and base

1 1

Total 10


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SECTION B

Q No. Explanation MarksTotal

Mark

7. (a) (i)

(ii)

(iii)

(b) (i)

Electron arrangement of argon atom is 2.8.8

Has 8 valence electrons / outermost shell is occupied by 8

electrons //has achieved stable/ octet electron arrangement

Group 1

Electron arrangement of lithium atom is 2.1, sodium atom 2.8.1and potassium atom 2.8.8.1Has 1 valence electron // has same valence electron

Period 3

Electron arrangement of sodium atom is 2.8.1, magnesium atom

2.8.2 and aluminium atom is 2.8.3

Have 3 shell occupied with electrons // same number of shell

occupied with electrons

1. electron arrangement of carbon atom is 2.4

2. electron arrangement of chlorine is 2.8.7

3. sharing electron4. to achieve octet electron arrangement

5. carbon atom contributes 4 electron and chlorine contributes 1electron // diagram

6. one carbon atom combine with 4 chlorine atom // diagram

1

1

1

11

1

1

1

1

1

11

1

1

2

3

3

6

Cll

Cl

Cl ClC


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Q No. Explanation MarksTotal

Mark

(ii) 1. electron arrangement of oxygen atom is 2.6

2. electron arrangement of sodium atom is 2.8.1

3. to achieve octet electron arrangement

4. sodium atom donate 1 electron to form Na

+

// diagramOxygen atom accept 2 electron to form O2-

5. electrostatic force between sodium ion and oxide ion

6. to form a compound with formula Na2O // diagram

1

1

1

1

1

1 6

Total 20

8. (a)

(b) (i)

(ii)

- Nucleus is at the centre of the atom.

- Atom contains one proton and one neutron //

proton number =1 and nucleon number = 2a : 1 number of proton

r : has 1 proton number, 1 number of nucleon

- electron moves around the nucleus // electron is locatedoutside the nucleus

- electron is negatively charged // the electron has -1 charged.

- electron arrangement is 1[any 4 points]

note : adp atom for element

- The same number of proton // same value of proton number

- The same number of electron // the same number of valence

electron

r : electron number / same valence electron

- The same chemical properties.

- Different number of neutron // different nucleon number

r : number of nucleon , neutron number- Different physical properties

a : comparison of any specific physical properties

[any 4 points]

H31 r: Y1

3

- state correct symbol of element for isotope H-3 ; H

- state correct of proton number (1) and nucleon number (3)

1

1

1

1

1

1

1

1

1

1

1

1

4

4

2

(c) At t0 t1

- element X is in liquid state

- the particles / molecules arrangement are closed but not in

orderly manner // not very closely pack

- the kinetic energy increases (as temperature increase)r : the particles move faster

At t1 t2- element X in (the mixture of) liquid and gas states

1

1

1

1

3

Na NaO

2 -+ +


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No Explanation MarksTotal

Mark

(b) (i)

CH2 C2H4

Type of

elements

Carbon and hydrogen Carbon and hydrogen

No of atom in

element

1 carbon atom and 2

hydrogen atoms

2 carbon atoms and 4

hydrogen atoms

Relative mass 14 28

1

1

1 3

(ii) [Experiment to determine the empirical formula of Y oxide]

Materials 10 cm Y ribbon/strip, sand paper

Apparatus crucible with lid, tongs, Bunsen burner, tripod stand,

pipe clay triangle, (electronic) balance

1

1 2


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Mark

Procedure :

1. A crucible with its lid is weighed.

2. Y strip is cleaned with sandpaper and is placed in a crucible.

3. The crucible, its lid and the contents are weighed again.

4. The crucible is heated strongly (until the Y lights up). As soon as

the Y starts to burn, the crucible is closed by its lid.

5. The heating is continued and the crucible lid is opened once in a

while // (open and shut in short of time.

6. When the magnesium tape is no longer burnt, the lid is

removed and the crucible is heated strongly (to ensure the

complete burning of the magnesium).

7. The crucible and its contents are left to cool to room

temperature and are weighed again.

Max marks for procedures is 5

1

11

1

1

1

1

5

Precautionary step:

The crucible and its contents are heated, cooled and weighed again

until a constant mass is obtained. 1 1

Tabulation of data:

Description Mass(g)

Crucible + lid a

Crucible + lid + Y b

Crucible + lid + Y oxide c 1 1

Calculation :

Mass of Y = b - a Mass of O = c - b

No of mole of Y = b - a no of mole of O = c - b

24 16

Simplest ratio r s

Empirical formula Yr Os

1

1

1 12

Total 20

10. (a) (i)

(ii)

Soluble salts : Potassium sulphate and zinc sulphate

Insoluble salt : Lead (II) sulphate

For K2SO4 : Potassium hydroxide and sulphuric acid (solution)

For ZnSO4 : Sulphuric acid (solution) and zinc (metal) / zinc oxide

1

1

1

1 4


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Heat


Mark

/ zinc carbonate

(b) [Experiment to prepare the dry soluble salt][Labelled diagram]

- functional diagram

- correctly labelled

[Method]

1. Heat the solution/mixture until saturated solution / crystal isformed.

2. Cool the mixture

3. Filter the salt crystals / solids.

4. Dry the salt by using filter papers.

1

1

1

1

1

1 6

(c) Acid A : hydrochloric acid / nitric acid / sulphuric acid.

Acid B : ethanoic acid / methanoic acid (or any organic acid)(examples of acids must be named)

Acid A / HCl is a strong acid.

It dissociates/ionize in water completely // It has the high

concentration of H+

ions in water (that lower the pH value).

Acid B / CH3COOH is a weak acid.

It dissociates/ionize partially in water. // It has low concentration of

H+

ion in water (that higher the pH value).Apply adp for in water

11

1

1

1

1 6

(d) Ethanoic acid / vinegar / lemon juice.

Reasons;

1. weak acid

2. neutralise the alkali

3. does not produce too much heat

4. less/not corrosive

Choose any 3 reasons

1

1

1

1

1

4

Total 20

END OF MARKING SCHEMEPERATURAN PEMARKAHAN BERAKHIR

Salt solution

Evaporating dish

chem answer paper 2 final

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