Kimia_total Revision Final Exam

CHEMISTRY PERFECT SCORE MODULE

SET

1. 2. 3. 4.



The Structure of Atom Chemical Formulae and Equations Periodic Table of Elements Chemical Bonds

Chemistry Perfect Score Module 2009

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PAPER 2 – STRUCTURE 1

SECTION A Graph 1 shows the cooling curve of molten naphthalene beginning from 90oC. Temperature/◦C

90 T

P

Q

R

0

t1

t2

t3

Time/min

Table 1 Based on Table 1, answer the following question. (a) State the melting point of naphthalene. …………………………………………………………………………………………………………………………… [1 mark] (b) State the time when all the liquid naphthalene has frozen . …………………………………………………………………………………………………………………………. [1 mark] (c) Why does the temperature of naphthalene remains constant from t1 to t2? …………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………….. [2 marks] (d) (i) What is the type of particles in naphthalene? …………………………………………………………………………………………………………………………… [1 mark] (ii) Draw the arrangement of particles of naphthalene at point P and R in the space provided.

Point P

Point R [2 marks]

(e) State the physical state of naphthalene during the time (i)

t1 to t2: ……………………………………………………………………………………………………….

(ii)

t2 to t3: …………………………………………………………………………………………………….. [2 marks] (f) When solid naphthalene is heated with direct flame and the physical state of naphthalene changes from solid to gas. Name the process that occurs. ……………………………………………………………………………………………………………………….

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[1 mark] 2

Table 2 shows four substances and their respective formulae Substance

Chemical Formula

Bromine Nickel Phenol Sodium chloride

Br2 Ni C6H5OH NaCl

Table 2 (a) State all substances that exist as molecules. ………………………………………………………………………………………………………………….. [1 mark] (b) Which substance is an electrolyte? …………………………………………………………………………………………………………………… [1 mark] (c) What is the physical state of bromine at room temperature? …………………………………………………………………………………………………………………… [1 mark] (d) State the substance that can conduct electricity in solid state ………………………………………………………………………………………………………………… [1 mark] (e) Draw the arrangement of the particles in the substance in (d) at room temperature.

[1 mark] (f)Name the particles present in sodium chloride. ……………………………………………………………………………………………………………………… [1 mark] (g) Graph 2 shows the temperature against time when solid phenol is heated. Temperature/◦ C S Q

T1 T0

R

P Time/s

Graph 2 (i) State the melting point of phenol. ………………………………………………………………………………………………………………………. [1 mark] (ii) Explain why there is no change in temperature from Q to R. ………………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………………. [2 mark] (iii) State how the movement of naphthalene particles changes between R and S during the heating. ……………………………………………………………………………………………………………………….. [1 mark]

Chemistry Perfect Score Module 2009

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3

Diagram 3 shows the set -up apparatus of an experiment to determine the empirical formula of copper (II) oxide. Copper(II) oxide Hydrogen gas Porcelain dish

Heat

Anhydrous calcium chloride, CaCl2 Diagram 3 (a)

What is the meaning of chemical formula?

(b)

.........………….………………………………………………………………………………......... [1 mark] State one precaution that must be taken before the copper (II) oxide is heated.

(c)

………….……...……………………………………………………………….......………………………. [1 mark] Table 3 shows the results of an experiment carried out by a student. Mass of combustion tube + porcelain dish Mass of combustion tube + porcelain dish + copper (II) oxide Mass of combustion tube + porcelain dish + copper Table 3 (i) Calculate the number of moles of copper in this reaction. [Relative atomic mass : Cu = 64]

30.24g 32.26g 31.86g

[1 mark] (ii)

Calculate the number of moles of oxygen in this reaction. [Relative atomic mass : O = 16]

(iii)

Determine the empirical formula of copper (II) oxide.

[1 mark]

(d)

[2 marks] Name another metal oxide that uses the same method to determine the empirical formula. ……..…………………………………………………………………………………….………… [1 mark]

(e)

M is a reactive metal. State how to determine the empirical formula of the oxide of M. ........................................................................................................................................... [1 mark]

Chemistry Perfect Score Module 2009

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4

Diagram 4 shows the apparatus set-up to determine the empirical formula of oxide metal M. M oxide

Dry hydrogen gas

Asbestos paper DIAGRAM 4 (a)

(i)

Name two chemicals used to prepare hydrogen gas in the laboratory. ................................................................................................................................... [2 marks]

(ii)

Write a chemical equation for the reaction in (a)(i). …………………………………………………………………………….………………... [1 mark]

(b)

Table 2 shows the result of the experiment: Mass of combustion tube + asbestos paper Mass of combustion tube + asbestos paper + M oxide before heating Mass of combustion tube + asbestos paper + product after heating (i)

Determine the empirical formula of M oxide. [Relative atomic mass of O=16, M=55]

(ii)

Write a chemical equation for the reduction of M oxide by hydrogen gas.

39.25 g 47.95 g 44.75 g

[3 marks]

................................................................................................................................... [1 mark] (c)

State one precaution that must be taken when carrying out the experiment. ............................................................................................................................................

(d)

[1 mark] Can the empirical formula of magnesium oxide be determined by the same method? Explain your answer. ............................................................................................................................................ ............................................................................................................................................ [2 marks]

Chemistry Perfect Score Module 2009

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5

Diagram 5 shows the set-up of apparatus for an experiment to determine the empirical formula of magnesium oxide. Lid Magnesium ribbon

Crucible

Diagram 5 Result: Mass of crucible + lid Mass of crucible + lid + magnesium ribbon Mass of crucible + lid + magnesium oxide

= 24.0 g = 26.4 g = 28.0 g

(a) What is meant by empirical formula? ................................................................................................................................... [1 mark] (b) Based on the above result, (i) calculate the mass of magnesium and the mass of oxygen that have reacted.

[1 mark] (ii)

calculate the mole ratio of magnesium atoms to oxygen atoms. [Relative Atomic Mass: O=16; Mg=24]

[1 mark]

(iii)

determine the empirical formula of magnesium oxide.

[1 mark] (iv)

write the chemical equation for the reaction in the experiment.

[1 mark] (c) Why was the crucible lid opened once in a while during the experiment? ................................................................................................................................... [1 mark] (d) Metal X is placed below hydrogen in the reactivity series. You are required to carry out an experiment to determine the empirical formula of the oxide of metal X. The apparatus provided are combustion tube, glass tube, cork, Bunsen burner, and porcelain dish. (i) Draw a labelled diagram of of the apparatus set-up for the experiment.

[2 marks]

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(e) Describe the steps that should be taken to ensure that all the air in the combustion tube has been expelled. ............................................................................................................................................................................. ............................................................................................................................................................................ .............................................................................................................................................................................. [3 marks] 6

Diagram 6 shows the symbols for atom of element X, Y, and Z.

X R

Y

Z Y

Diagram 6 (a)

(i) Write the electron arrangement of atom X. ………………………………………………………………………………...… [1 mark] (ii) State the period and the group for element X in the Periodic Table. Period : ….…………………………………………………………….. Group : ………………………………………………….……….......... [2 marks]

(b)

(i) What is the proton number of element Z? ....................................................................................................................................................... [1 mark] (ii) Atom of element Y has a nucleon number of 35. Calculate the number of neutrons in atom Z. …………………………………………………………………………………………………. [1 mark] (iii) Write the the standard representation of element Z ....................................................................................................................................................... [1 mark]

(b)

Element Y and Z are located in the same Group in the periodic table of element. Compare reactivity of element Y and Z. Explain your answer ………………………………………………………………………………………………………........................... …………………………………………………………………………………………………………………………… …………………………………………………………………………………..................................................... [4 marks]

(c)

Element X can react with sodium to form a compound (i)Name the type of bond in the compound formed between atoms X and sodium. …………………………………………………………………………………...................................................... [1 mark]

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(ii) Give one physical property of the compound in (c)(i). …………………………………………………………………………………......................................................... [1 mark] (d)

Element X can also react with carbon to form a compound. Draw the electron arrangement for the compound formed. [ Proton number of C = 11 ]

[2 marks] 7

Table 7 shows the proton numbers of elements X, Y and Z. Elements

Proton Number

X Y Z

12 8 6

a)

Table 7 Write the electron arrangement for atom X

b)

………………………………………………………………………………………………………………… [1 mark] X and Y react to form a compound i)

What type of bond holds atom X and Y together?

……………………………………………………………………….……………………………………….. [1 mark] ii)

What will happen to atom X during the formation of the compound with atom Y? Explain why. ……………………………………………………………………….................................................. ………………………………………………………………………...................................................

…………………………………………………………………………………………………………… [2 marks] iii) Draw the electron arrangement of the compound formed in (b)(ii)

[2 marks] iv) State one physical property of the compound formed ……………………………………………………………................................................................ [1 mark]

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c)

Z can react with Y to form a compound. i)

What is the molecular formula of the compound formed? …………………………..................................................................................................... [1 mark]

ii)

What is the relative molecular mass of the compound in c(i). [ Given that relative atomic mass Z = 12; Y= 16] …………………………………………………………………………………………………….. [1 mark]

iii)

Name another compound that has the same physical properties as the compound formed. …………………………………………………………………………..................................... [1 mark]

Diagram 8 shows the position of several elements P, Q, R, S, T, U and W.

8

P Q

T

R

S

V

U W

X

Diagram 8 Using the symbols P, Q, R, S, T, U and W, answer the following questions. (a) State one metal and one non- metal Metal:….…………………….…… Non-metal:………………………. [1 marks] (b) Write the electron arrangement of atom V. ..………………………………………………………………………………………………………………………. [1 mark] (c) Which of the elements has the biggest atomic radius? ……………………………….………………………………………………………………………………………… [1 mark] (d) (i) Compare the electronegativity of elements Q, T, V and U. ………………………………………..…………………………………………………………………………… [1 mark] (ii) Explain your answer in (d)(i). ……………………………………………………………………………............................................……… ……………………………………………………………………………………............................................. ……………………………………………………………………………............................................……… …………………………………………………………………………………….......................................... [4marks]

Chemistry Perfect Score Module 2009

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(e) State the ion formed by Q. ..…………………………………………………….………………….……………………………………………… [1 mark] (f) (i) Which element is chemically inert? …....…………………………………………………………………..…………………………………………….…. [1 mark] (ii) Explain your answer. …....…………………………………………………………………..……………………………………………… [1 mark] (g) Write an equation for the reaction between R and U. …....…………………………………………………………………..…………………………………………………. [1 mark] (h) Give one special characteristic of S. ……….………………………………………………………………..…………………………………………………. [1 mark] 9

Diagram 9 shows the chemical symbols which represent element P, Q, R and S. 23 11 (a)

(i)

P

16 8

Q

14 6

R

35 17

S

Diagram 9 Write the electron arrangement of atom Q. ………………………………………………………………………………...……………………

(ii)

[1 mark]

State the period and the group for element Q in the Periodic Table. Period : ….…………………………………………………………….. Group : ………………………………………………….………........... [2 marks]

(b)

Atoms of P and Q can react to form a compound. (i) Name the type of bond in the compound formed between atoms P and Q. ……………………………………………………………………………………………………… (ii)

(c)

[1 mark]

Draw the electron arrangement for the compound formed.

[2 mark] Atoms of R and S can also react to form a compound. Draw the electron arrangement for the compound formed.

[ 2 marks]

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(d)

Compare one physical property of compound formed (b) and (c). Explain your answer. ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………[4 marks]

10

Table 10 shows the melting point, boiling point and electrical conductivity of substances P, Q, R, and T .

Substance

Melting point (oC)

Boiling point (oC )

Electrical conductivity Solid

Molten

P

805

1460

No

Yes

Q

1549

2950

Yes

Yes

R

-210

-153

No

No

T

-7

59

No

No

Table 10 (a) Which of the substances is a metal ? ……………………………………………………………………………………………………………………….. [1 mark] (b) (i) State the type of particle in substance P ? …………………………………………………………………………………………………………………………. [1 mark] (ii) Explain why substance P cannot conduct electricity in solid form but can conduct electricity in molten state. ............................................................................................................................................................. ............................................................................................................................................................. [2 marks] (c) (i) What is the physical state of R and T at room temperature ? R : ............................................ T : ............................................ [2 marks] (ii) Draw the arrangement of particles in substance T at room temperature .

[2 marks] (iii) Explain why the melting and boiling points of substance R and T is low ?

………………………………………………………………………………………………………………………………..

……………………………………………………………………………………………………………………………….. [2 mark]

Chemistry Perfect Score Module 2009

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PAPER 2 ESSAY SECTION B 11 (a) Diagram 11.1 shows two isotopes of an element X 35 17

37

X

17

X

Diagram 11.1

(i) State the number of neutron in each isotope

[ 2 marks]

(ii) State two similarities and two differences between the isotopes [4 marks] (b) Diagram 11.2 shows an atom of element P. The letter used is not the actual symbol of the element. \

X R

6p + 6n

Diagram 11.2 . (i) Describe the atom shown in Diagram11.2 (ii)

[4 marks] Another atom of element P has 7 neutrons. Compare this atom with the atom in Diagram 11.2 [4 marks]

(c) X is a substance which melts at 71oC and boils at 314oC (i) Sketch a graph of temperature against time when molten X at 100oC is cooled to

60oC. [2 marks]

o

(ii) Based on the graph in (c)(i), state the physical state of substance X at 71 C and explain the changes in terms of the kinetic energy and the arrangement of particles [4 marks] 12 3

1 mole of any gas occupies 24 dm at room condition. (a)

Explain why 16 g of oxygen occupies the same volume as 22 g of carbon dioxide at room condition. [ 4 marks ]

(b) Caffeine is one of the substances in coffee. 0.97 g of caffeine consists of 0.48 g carbon, 0.05 g hydrogen, 0.28 g nitrogen and 0.16 g oxygen. The molar mass of caffeine is 194 g mol –1. Based on the information above, Determine the empirical formula and molecular formula of caffeine. [8 marks] (c) Fertilisers usually have a high content of nitrogen. Nitrogen is needed to increase the growth of plants such as vegetables. The following substances are the examples of fertiliser which are used by farmers . ♦ Ammonium suplhate, (NH4)2SO4 ♦ Urea, CO(NH2)2 ♦ Hydrazine, N2H2 Calculate the percentage of nitrogen by mass in each of the three fertilizers given above and hence determine the best fertiliser a farmer should used for his plants.

Chemistry Perfect Score Module 2009

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[ 8 marks ]

13. (a) Diagram 13.1 shows the standard representation for sodium element

Diagram 13.1 State three information that can be deduced from the diagram Draw the atomic structure of sodium atom . [6 marks]

Chemistry Perfect Score Module 2009

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(b) Diagram 13.2 shows the empirical formula of glucose :

Diagram 13.1 (i) What is the meaning of empirical formula ? (ii) The relative molecular mass of glucose is 180, determine the molecular formula of glucose [4 marks] (c) (i)

A chloride of iron contains 2.80 g of iron and 5.32 g of chlorine. Determine the empirical formula of the compound. [ Relative atomic mass : Fe = 56 , Cl = 35.5 ] [4 marks]

(ii) Write a chemical equation to represent the reaction between iron and chlorine. Calculate the volume of chlorine gas that reacts completely with 2.80 g iron. 3 [ 1 mole of gas occupied 24 dm at room temperature and pressure ] [6 marks] 14

(a) What is meant by empirical formula? [1 mark] (b) A carbon compound contains 92.3% of carbon and 7.7% of hydrogen by mass. The relative molecular mass of this compound is 78. Find the molecular formula of this compound. [Relative atomic mass: C=12; H=1] (c) Describe how you could determine the empirical formula of magnesium oxide in the laboratory. Your description should include • procedure of experiment • tabulation of result • calculation of the results obtained [Relative atomic mass: O=16; Mg=24]

[5 marks]

[11 marks]

(d) Magnesium can reduce copper oxide to copper. Explain why the empirical formula of the copper oxide cannot be determined by heating the mixture of copper oxide and magnesium powder. [2 marks]

Chemistry Perfect Score Module 2009

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PAPER 2 ESSAY SECTION C 15 (a) Diagram 15 shows the electron arrangement of a compound formed from the reaction between element Y and element Z These letters are not the actual symbols of the elements.

+

Y

Z

Diagram 15 (i) Based on diagram 15 , write the electron arrangement for atoms of element Y and Z. Explain the position of element Y in the Periodic Table of the Elements. [6 marks ] (ii) Element Y can react with sodium and sodium hydroxide to form compounds. Write the chemical equation to represent the reaction . [4 marks ] (b) Table 15 shows the proton number for atoms P , Q and R. These letters are not the actual symbols of the elements. Elements

Proton number

P Q R

11 17 6 Table 15

Using the information in table 15, explain how two compounds can be formed from these elements . The two compounds should have different bond types. [10 marks ]

Chemistry Perfect Score Module 2009

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PAPER 3 STRUCTURE 16 An experiment is conducted to find out the freezing point of liquid naphthalene. A boiling tube containing molten naphthalene at 95 ° C is allowed to cool in a conical flask to room temperature. The temperature of naphthalene is recorded at half-minute intervals. Diagram 1 shows the reading of the thermometer for this experiment.

95

90

90

90

90

85

85

85

85

80

80

80

Initial temperature

Temperature at

Temperature at

Temperature at

0 s : ………

30 s : ………

60 s : ………

90 s : ………

85

85

85

85

80

80

80

75

75

75

70

Temperature at

Temperature at

Temperature at

Temperature at

120 s : ………

150 s : ………

180 s : ………

210 s : ………

Diagram 16 (a) Record the temperature in the spaces provided in Diagram 16. [3 marks] (b) Construct a table to record the data shown in Diagram 16.

[3 marks] (c)

(i)

Draw a graph of temperature against time. [3 marks]

(ii)

On your graph , mark the freezing point of naphthalene.. [3 marks]

Chemistry Perfect Score Module 2009

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(d)

(i)

What is meant by freezing point ? ………………………………………………………………………………………………………………

(ii)

th

Explain why the temperature of naphthalene remains constant form 90 seconds during the cooling process.

[3 marks] th seconds to 150

……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………. [3 marks] (e) Why is the boiling tube placed in the conical flask during the cooling process ? ……………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………… [3 marks]

Chemistry Perfect Score Module 2009

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(f) Diagram shows the arrangement of particles of four substances. Na Na

Na

Na

Na

Na

Na

Na

Na

+

+

-

Na

Cl-

Na

Cl

Cl-

Na+

Cl-

Na+

Na

Na

Na

+

Na

Cl

P

-

+

Na

Cl

-

Q

O

Cl Cl

O O

Na

H

O

Cl Cl

Cl Cl

H

O

H

S

Classify P, Q , R, and S into element and compound. Element

Compound

[ 3 marks ]

17

A student carried out an experiment to determine the empirical formula of magnesium oxide. The step and set-up of apparatus of the experiment are shown in Diagram 17.

Step 1. Crucible and lid are weighed

Set-up of apparatus

2. Crucible, lid and magnesium ribbon are weighed

3. Magnesium and ribbons heated until the reaction is complete

4. Crucible, lid and magnesium oxide are weighed when cold

Diagram 17

Chemistry Perfect Score Module 2009

O

O

Cl Cl

R

H

30

O

(a) Complete the following table by stating the observations and related inferences in the experiment. Observation

Inferences

(i)

(i)

(ii)

(ii)

[6 marks] (b) Record the reading to two decimal places for The mass of crucible and lid :…………….g The mass of crucible, lid and magnesium ribbon: …………. g The mass of crucible, lid and magnesium oxide when cold: ………… g [3 marks] (c) (i) What is the mass of magnesium that has been used?

(ii) What is the mass of oxygen which reacted with magnesium?

(iii) Determine the empirical formula of magnesium oxide. Use the information that the relative atomic mass, Mg = 24 and O = 16

[3 marks] (d) Based on your answer in (c)(iii), how many moles of magnesium and oxygen atoms have reacted?

[3 marks]

Chemistry Perfect Score Module 2009

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BAHAGIAN PENGURUSAN SEKOLAH BERASRAMA PENUH DAN SEKOLAH KLUSTER

MODUL PERFECT SCORE 2009

CHEMISTRY

ANSWERS

Answer Chemistry Perfect Score Module 2009

1

STRUCTURE PAPER 2 Answer 1 o (a) T C (b) t2 (c) Heat energy released to the surroundings is balanced by the heat release by the particles attract one another to form a solid (d)(i) molecules (ii) P: R

(e)(i) liquid and solid (ii)Solid (f) Sublimation

Mark 1 1 1 1

1+1

1 1 1 …….10

2. (a) bromine and phenol (b) Sodium chloride (c) liquid (d) Nickel (e)

1 1 1 1 1

(f) ion (g) (i) T1 (ii) Heat is absorbed by the particles/molecules is used to overcome the attraction forces between the particles/molecules in solid naphthalene. (ii) Become faster A representation of a chemical substance using letters for atoms and subscripts for each type of atoms present in the substance.

3 (a)

Flow hydrogen gas must through the combustion tube for a few minutes before heating/The flow of hydrogen gas must be continuous throughout the experiment

(b) (c )(i) (ii) (iii)

(d) (e)

Number of mole of copper = 1.62 64 = 0.025 mol Number of mole of oxygen = 0.40 16 = 0.025 mol Number of mole of copper : Number of mole of oxygen 0.025 : 0.025 The simplest ratio 1 : 1 The empirical formula of copper(II) oxide is CuO Iron oxide / Tin oxide / Lead(II) oxide / Silver oxide/ Aurum oxide / Burning of metal in excess oxygen

Answer Chemistry Perfect Score Module 2009

1 1 1 1 1 ……10 1

1

1 1 1 1 1 …..7

2

4

(a)

(i)

(b)

(ii) (i)

Zinc hydrochloric acid / suphuric acid Zn + 2HCl
ZnCl2 + H2

1 1 1 1 1 1

Empirical formula is MO2 ( c) (d)

(ii) MO2 + 2H2
M + 2H2O The air in the combustion tube must be displaced before lighting the hydrogen gas// The heating, cooling and weighing is repeated until a constant mass is obtained

1 1

No. Magnesium is more reactive than hydrogen.

1 1

5 (a) The chemical formula that shows the simplest ratio of the number of atoms of each type of elements in the compound 1 (b) (i) Mass of magnesium = (26.4-24.0)g =2.4 g Mass of oxygen = (28.0 – 26.4) g = 1.6 g 1 (ii) The number of moles magnesium atoms =2.4 = 0.1 24 The number of moles oxygen atoms =1.6 = 0.1 16 0.1 mole of magnesium combines with 0.1 mole oxygen. Therefore, 1 mole of magnesium atoms combines with 1 mole of oxygen atoms. 1 (iii) The empirical formula of magnesium oxide is MgO. 1 (iv) 2Mg + O2
2MgO 1 (c) To allow oxygen to enter the crucible for complete combustion to occur. 1 (d) (i) X oxide Dry hydrogen gas → Heat (ii) Collect the gas in a test tube Place a burning wooden splinter at the mouth of the test tube No pop sound. 6 (a)

(i) (ii)

(b)

(i) (ii) (iii)

(iv)

(c)

(i) (i)

1+1 1 1 1 …..11

2.8.4 Period : 3 Group : 16 17 18 35 X 17

1 1 1 1 1

-Element Y is more reactive than element Z. - The size of atom Y is smaller tha atom Z -The attraction forces between nucleus and valence electron of atom Y is stronger than atom Z -it is easier for atom Y to receive valence electron compare to atom X.

1 1 1

Ionic bond Has high melting and boiling point// Conduct electricity in aqueous solution and

1 1

Answer Chemistry Perfect Score Module 2009

1 1

1

3

molten state // Soluble in water // insoluble in organic solvent ….13

(d)

O

C

O

1 1 …………16

Correct number of atom C and O Correct number electrons and shells

7 (a) (b)

(i) (ii) (iii)

2.8.2 Ionic bond -Atom X releases 2 electrons to atom Y 2+ - to achieve octet electron arrangement / to form ion X . Each ion drawn correctly

1 1 1 1

2Y

X

(iv) (c)

(i) (ii) (iii)

Number of electrons for ion X and ion Y are correct Charge of ions and ratio of ion X to ion Y are correct Has high melting and boiling point// Conduct electricity in aqueous solution and molten state // Soluble in water // insoluble in organic solvent ZY2 12 + 2(16) / 44 Name any covalent compound

1 1 1 1 1 1

……10 8

(a)

1

(b)

Metal : P/Q/R/S/T Non-metal : V/U/W/X 2.8.5

(c)

R

1

(i)

Electronegativity increases from Q to U

1

(ii)

-

1

(d)

-

(g) (h)

1

Q+

1

(i)

X

1

(ii)

Atom X has achieved octet electron arrangement

1

2R

1

(e) (f)

All atoms have same number of shells/Number of proton in the nucleus increases from Q to U The nuclei attraction forces between electrons and nucleus increases from Q to U The atomic size decreases from Q to U The tendency to receive electrons increases from Q to U

1

+

U2

→ 2RU

1. form coloured ions 2. has more than one oxidation number 3. as catalyst 4. form complex ions [ any one]

Answer Chemistry Perfect Score Module 2009

1

…..11

4

9 (a)

(i) (ii)

(b)

(i) (ii)

2.6 Period : 2 Group : 16 Ionic

1 1 1….2 1 2+

+ P

Q

+ P

Number of electrons for ion X and ion Y are correct Charge of ions and ratio of ion X to ion Y are correct

1 1….2

(c)

Correct number of atom R and S Correct number electrons and shells

1 1….2

(d)

-

1

-

Compound in (b) cannot conduct electricity when in solid state but it can conduct electricity at molten or aqueous state . Compound in (c) cannot conduct electricity at any state Compound in (b) consist of ions while Compound in (c) consist of neutral molecules Ions in compound (b) are not free to move at solid state and the molecules in (c) Neutral molecules in compound (b) are not free to move at solid state and the molecules move freely at molten/aqueous state

@ - The melting point of compound (b) is higher than compound (c) - Compound in (b) consist of ions while Compound in (c) consist of neutral molecules - Ions in compound (b) are attracted by strong electrostatic forces while molecules in compound (c) are attracted by weak van der Waals forces - More heat energy is needed to overcome the strong electrostatic forces between ions in compound (b) compared to weak van der Waalls forces between molecules in compound(c)

1 1 1

1 1 1 1….4 ….12

10 (a) (b)(i) (b)(ii) (c)(i)

Q Ion solid state : Ions are not freely moving// ions are in a fixed position. molten state : Ion can move freely R : Gas T : Liquid

1 1 1 1…..2 1 1…..2

(c)(ii) 2

(c)(iii)

-

Van der waal/intermolecular forces between molecules are weak Small amount of heat is required to overcome it

1 1 .......10

Answer Chemistry Perfect Score Module 2009

5

ESSAY PAPER 2 QUESTION: 11 (a) (i) The number of neutrons : 18 and 20 respectively

2

(ii) Similarities

Differences

1. having the same proton number/number of electrons

1. different in the number of neutrons /different in the nucleon number

2. having the same valence electron/ having the same chemical properties

2. different in physical properties 4 1 1 1 1 …….4

(b)(i) 1. Nucleus contains 6 proton and 6 neutron 2. Electrons move around the nucleus 3. Two shells are filled with electrons 4. There are 6 valence electron// electron arrangement is 2.6 (ii) Comparison Proton number Number of valence electron Chemical properties Number of neutron//nucleon number Physical properties Standard representation of element

Diagram 1.2 6 4 similar 6//12 different different Any four

Another atom 6 4 similar 7//13 different different 4

(c) - Correct curve - Mark 71 on the y axes which is at the same level with the - X and Y axis with correct title and unit

1 1 1……3

Temperature/ ◦ C 100 71 60 Time/s (ii)

12

(a)

1 2. 3. 4.

Able to explain correctly 1. 2. 3. 4.

(b)

Substance X in both solid and liquid state 1 heat energy is released 1 kinetic energy of particles decreases 1 They are closer to each other // Attraction force between the particles become stronger 1……4 20

Number of mole in 16 g of oxygen = 16/32 // 0.05 mole Volume occupied by 16 g of oxygen = 0.05 mole x 24 dm-3// 12 dm-3 Number of mole in 22 g of CO2 = 22/44 // 0.05 mole Volume occupied by 22g of CO2 = 0.05 moles x 24 dm-3 // 12 dm-3

1 1 1 1…..4

Able to determine the empirical formula and molecular formula of caffeine correctly Element C H N O Mass /g

0.48

0.05

Answer Chemistry Perfect Score Module 2009

0.28

0.16

1

6

Number of mole The simplest ratio

0.48/12 //0.04

0.05/1 //0.05

0.28/14 //0.02

0.16/16 //0.01

0.04/0.01 // 4

0.05/0.01 // 5

0.02/0.01 // 2

0.01/0.01 // 1

1

1 1 1 1 1…..8

Empirical formula = C4H5N2O [C4H5N2O ]n = 194 [ 97 ]n = 194 n = 194/97 // 2 Molecular formula = C8H10N4O2 (c)

1

Able to calculate the molar mass and the percentage of nitrogen by mass in each of the three fertilisers and choose the best fertiliser. 1 molar mass of ammonium sulphate = 132g/mol 2 percentage of nitrogen in ammonium sulphate = 28/132 x 100% // 21.2% 3 molar mass of urea = 60 g/mol 4 percentage of nitrogen in urea = 28/ 60 x 100% // 46.7% 5 molar mass of hydrazine = 32g/mol 6 percentage of nitrogen in hydrazine = 28/132 x 100% // 87.5% 7 Hydrazine has the richest source of nitrogen compares with other fertilizers. 8 The farmer should choose hydrazine

1 1 1 1 1 1 1 1…..8 20

13

(a)

(b)

1. The proton number is 11 // Number of proton is 11 2. Nucleon number is 23 // Atomic mass is 23 3. Number of neutron = 23-11 = 12 4. Nucleus contains 11p and 12n 5. Position of electron circulating the nucleus 6. Correct number shell consists of electron 7. Symbol of sodium is Na any 6

(i) (ii)

(c)

(i)

Formula that show simplest ratio number of atoms of each element in compound 1. Relative molecular mass for n(CH2O) = 180 // 12n + 2n + 16n = 180 2. n = 6 3. C6H12O6 1. 2. 3.

Element Mass/g No. of moles Ratio of moles/ Simplest ratio

Fe 2.80 2.80/56 = 0.05 0.05/0.05 = 1

4. Empirical formula = FeCl3 (ii)

1. 2. 3.

Formula of the reactants Formula of products Balance equation 2Fe

+

3Cl2

→

Cl 5.32 5.32/35.5 = 0.15 0.15/0.05 = 3

1 1 1 1 1 1.....6

1 1 1 1 ....4 1 1 1 1...4 1 1 1

2FeCl3

Answer Chemistry Perfect Score Module 2009

7

4. 5. 6.

No. of moles Fe = 2.80/56 = 0.05 mol No. of moles Cl2 = (0.05 x 3)/2 = 0.075 mol Volume of Cl2 = 0.075 x 24 = 1.8 dm3 / 1,800 cm3

1 1 1 ...6 20

14

(a)

Formula that shows the simplest ratio of the number of atoms for each element in the compound.

(b)

(c)

Element Mass (%)

C 92.3

H 7.7

Number of moles

92.3 = 7.7 12

7.7 = 7.7 1

Ratio of moles

1

1

1…1

1 1 1

Empirical formula : CH RMM of (CH)n = 78 [ 12 + 1]n = 78 13 n = 78 n = 6 Molecular formula : C6H6 Procedure: 1. Clean magnesium ribbon with sand paper 2. Weigh crucible and its lid 3. Put magnesium ribbon into the crucible and weigh the crucible with its lid 4. Heat strongly the crucible without its lid 5. Cover the crucible when the magnesium starts to burn and lift/raise the lid a little at intervals 6. Remove the lid when the magnesium burnt completely 7. Heat strongly the crucible for a few minutes 8. Cool and weigh the crucible with its lid and the content 9. Repeat the processes of heating, cooling and weighing until a constant mass is obtained Record all the mass 10. Results: Mass/g Crucible + lid x Crucible + lid + magnesium y Crucible + lid + magnesium oxide z Calculations:

1 1…5 1 1 1 1 1 1 1 1 1

1 1 1

Element Mass (g)

Mg y-x

O z-y

y−x 24

z−y 16

a

b

Number of moles Empirical formula: MgaOb / MgO Simplest ratio of moles

(d)

15

(a) (i)

1 1 14... Max 12

- Cannot separate copper from magnesium oxide - Cannot weigh copper Atom Y : 2.8.7

Answer Chemistry Perfect Score Module 2009

1 1 20 1

8

(ii)

15 (b)

Atom Z : 2.8.8.1

1

Group 17 Because atom Y has 7 valence electron Period 3 Because atom Y has three shells occupied with electrons

1 1 1 1….6

2Na + Y2 → 2NaY Correct formula of reactants and product correct Balance equation

1 1

→ NaY + NaOY + H2O Y2 + 2NaOH Correct formula of reactants and products correct Balance equation

1 1…4

Ionic compound/bond 1- The electron arrangement of atom P = 2, 8, 1 / 2. 8. 1 // The electron arrangement of atom Q = 2, 8, 7 / 2. 8. 7

1

2- to achieve the stable electron arrangement

1

3- atom of P donates / gives one electron to the atom of Q to form P+ // half equation

1

4 - atom of Q receives / accepts one electron from atom of P to form Q// half equation

1

+

-

5 -the P ion and Q ions are attracted by a strong electrostatic force to form ionic bond .

1

6- with formula PQ / correct diagram

1

Covalent compound / bond 7-The electron arrangement of atom R = 2, 6 / 2. 6

1

8-to achieve the stable electron arrangement

1

9-[atom R and atom Q share electrons]

1

10 - atom R contributes 4 electrons and atom Q contributes one electron

1

11- one atom R and 4 atom Q share 4 pairs of electrons

1

12- to form covalent compound with the formula RQ4 / diagram

1 Max 10

Answer Chemistry Perfect Score Module 2009

9

STRUCTURE PAPER 3 Explanation 16 (a)

(b)

Score

Suggested Answer (a) 0 s = 95.0 ° C, 30 s = 85.0 ° C, 60 s = 82.0 ° C, 90 s = 80.0 ° C, 120 s = 80.0 ° C,150 s = 80.0 ° C, 180 s = 78.0 ° C, 210 s = 70.0 ° C. Suggested Answer

3

3 Time (second) 0.0 30.0 60.0 90.0 120.0 150.0 180.0 210.0

Temperature (° C) 95.0 85.0 82.0 80.0 80.0 80.0 78.0 70.0

(c) (i) & (ii) [ Score 3 & 3 ]

Temperature / ° C

95 90

x x x

80.0

x

x

x

Freezing point

x x

70

60

30

60

90

Answer Chemistry Perfect Score Module 2009

120

150

180

210

Time / second

10

d(i) d(ii) e

f

Suggested Answer The constant temperature at which liquid becomes a solid Suggested Answer The heat released when the particles in the liquid arrange to form solid balanced by the heat loss to the surroundings. Suggested Answer The air trapped in the conical flask is a poor conductor of heat. The air helped to minimize heat loss to the surroundings. / to ensure uniform cooling. Suggested Answer Element Compound P, R Q, S

3 3

3 3

17 (a) Observation (i) White fume is released (ii) White solid is formed/The mass of crucible and its content increases.

Inference (i) Magnesium oxide is formed (ii) Magnesium reacts with oxygen

(b) The mass of crucible and lid = 25.35 g. The mass of crucible, lid and magnesium ribbon =27.75 g. The mass of crucible, lid and magnesium oxide when cooled = 29.35g (c) (i) (ii) (iii)

The mass of Mg= (27.75 -25.35)g =2.40g The mass of O2=(29.35-27.75)=1.60 g The number of moles Mg=0.1 mole The number of moles O = 0.1 mole The ratio of Mg : O = 1 : 1 The empirical formula is MgO.

(d) 0.1 mole of Mg reacts with 0.1 mole of O/1 mole of Mg reacts with 1 mole of O 18 (a)

Able to predict the manipulated variable, the responding variable and the constant variable completely. Manipulated variable : metals of Group 1 elements // sodium, lithium, potassium.

Able to state how to control the manipulated variables correctly

Responding variable: the reactivity of the reaction with water // the speed of movement on the water surface

Able to state correctly the way to control the manipulated variable To observe how fast the metals move on the surface of water.

Constant variable: size/mass of metals. Volume of water

Repeat the experiment by using the metals of sodium, lithium and potassium

Able to use the metal granules with the same size Use the metal granules with the same size.

18 (b) Able to state the relationship between the manipulated variable and the responding variable correctly..

18 (c) 18 (d)

Suggested answer: The reactivity of Group 1 elements increases going down the group. Able to arrange correctly the reactivity series of the metals according to descending order. Answer: potassium, sodium, lithium Able to classify the ions correctly. [to name or write all the formula of the ions correctly at the cations and anions group.] Answer: positive ion/ cation : sodium ion/ Na+, hydrogen ion/ H+ Negative ion/anion : hydroxide ion/ OH-

Answer Chemistry Perfect Score Module 2009

11

RIVISION Neutralisation 2. Diagram 1 shows the apparatus set-up for the neutralisation reaction between a strong acid and a strong alkali. Rajah 1 menunjukkan susunan radas untuk tindak balas peneutralan antara satu asid kuat dan satu alkali kuat.

Hydrochloric acid, 0.1 mol dm-3

25 cm3 sodium hydroxide solution + phenolphthalein 25 cm3 larutan natrium hidroksida + fenolftalein DIAGRAM 1 3

25.0 cm of sodium hydroxide solution is poured into a conical flask. A few drops of phenolphthalein are added into the solution. The solution in the conical flask is titrated with -3 0.1 mol dm hydrochloric acid . 25.0 cm3 larutan natrium hidroksida dimasukkan ke dalam sebuah kelalang kon. Beberapa titik fenolftalein ditambah ke dalam larutan itu. Larutan dalam kelalang kon dititratkan dengan 0.1 mol dm-3 asid hidroklorik. (a)

Hydrochloric acid is a strong acid. What is meant by a strong acid? Asid hidroklorik adalah asid kuat. Apakah yang dimaksudkan dengan asid kuat? ………………………………………………………………………………… ………………………………………………………………………………… [2 marks]

(b)

Suggest an apparatus that can be used to measure 25.0 cm3 of sodium hydroxide solution accurately. Cadangkan satu radas yang dapat digunakan untuk menyukat 25.0 cm3 larutan natrium hidroksida dengan tepat. ………………………………………………………………………………… [1 mark]

(c)

State the colour change of the solution in the conical flask at the end point. Nyatakan perubahan warna larutan dalam kelalang kon pada takat akhir. ………………………………………………………………………………… [1 mark]

(d)

(i)

Write a chemical equation for the above reaction. Tulis persamaan kimia bagi tindak balas di atas. …………………………………………………………………………… [1 mark]

(ii)

In this experiment, 20.0 cm3 hydrochloric acid is needed to neutralise 25.0 cm3 of sodium hydroxide solution. Calculate the molarity of the sodium hydroxide solution. Dalam eksperimen ini, 20.0 cm3 asid hidroklorik diperlukan untuk meneutralkan 25.0 cm3 larutan natrium hidroksida. Hitungkan kemolaran larutan natrium hidroksida itu.

[2 marks] (e)

(i)

The experiment is repeated with 0.1 mol dm-3 sulphuric acid to replace hydrochloric acid. Predict the volume of sulphuric acid needed to neutralise 25.0 cm3 sodium hydroxide solution. Eksperimen itu diulang dengan menggunakan 0.1 mol dm-3 asid sulfurik bagi menggantikan asid hidroklorik. Ramalkan isipadu asid sulfurik yang diperlukan untuk meneutralkan 25.0 cm3 larutan natrium hidroksida. …………………………………………………………………………… [1 mark]

(ii)

Explain your answer in (e) (i). Terangkan jawapan anda dalam (e)(i). …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… [2 marks]

Answer 1. (a)

An acid that dissociates/ ionises completely in water to form a high concentration of hydrogen ions pipette From pink to colourless (i) HCl + NaOH Æ NaCl + H2O (ii) 0.1 x 20 = 1 Mb x 25 1

(b) (c) (d)

(e)

(i) (ii)

1 1 1 1

25 Mb = 2 Mb = 0.08 mol dm-3 10 cm3 // half the volume of hydrochloric acid 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 . Total

Chemical bond Figure 1 shows the electron arrangement for atoms P, Q and R.

Q

R

P

FIGURE 1 Based on figure 1, answer the following questions: (a)

(i)

State the location of atom R in the Periodic Table of Elements.

(ii)

Explain how you determine the group and the period of atom R. [5 marks]

(b) Atoms P and Q can form chemical bonds with atom R. State the type of chemical bond and explain how the bond is formed between: (i)

Atoms P and R

(ii)

Atoms Q and R

[11 marks] (c)

State one physical property of the compound formed in (b) (i) and the compound formed in (b) (ii). Explain the differences in the physical property stated. [4 marks]

Answer 1

(a)

(i)

Atom R is located in Group 17, Period 3

(ii)

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

1+ 1 1 1

It is in Period 3 because it has three shells filled with electron 1

5 (b)

(i)

Atoms P and R form covalent bond.

1

To achieve the stable electron arrangement,

1

atom P needs 4 electrons while atom R needs one electron.

1

Thus, atom P shares 4 pairs of electrons with 4 atoms of R, forming a molecule with the formula PR4 // diagram

1

1 R

R

P

R

R

(ii)

Atom Q and atom R form ionic bond.

1

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

1 1

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

Q

Atom R receives an electron to form ion R-//equation and achieve a stable octet electron arrangement. R+e

1

1

-

R

Ion Q+ and ion R- are pulled together by the strong electrostatic forces to form a compound with the formula QR// diagram 1

+ Q

(c)

R

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

1

while the covalent compound / (b)(i)does not dissolve in water.

1

Water is a polar solvent that can cause the ionic compound to dissociate into ions.

1

11

Covalent compounds are non-polar and can only dissolve in organic solvents.

1 4

OR The melting point of the ionic compound/ (b)(ii) is higher than that of the covalent compound/ (b)(i) .

1 1

This is because in ionic compounds ions are held by strong electrostatic forces. 1 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.

1

OR

The ionic compound/(b)(ii) conducts electricity in the molten or aqueous state whereas the covalent compound/(b)(i) does not conduct electricity.

1

max

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

1

4/5

Covalent compounds are made up of molecules only

1

1

4 Total

20