STPM Trials 2009 Chemistry Paper 2 (Pahang)

8/3/2019 STPM Trials 2009 Chemistry Paper 2 (Pahang)

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Identity card number................................................ Centre number/index number: ............................

(Nombor kad pengenalan) (Nombor pusat/angka giliran)

962/2

TRIAL STPM 2009(PEPERIKSAAN PERCUBAAN STPM 2009)

CHEMISTRY (KIMIA)

PAPER 2 (KERTAS 2)

Two and a half hours (Dua jam setengah)

For examiners use

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2

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5

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9

10

Total

This question paper consists of 9 printed pages.

Instructions to candidates:

DO NOT OPEN THIS QUESTION PAPER UNTIL

YOU ARE TOLD TO DO SO.

Answerall questions in section A. Write your answers in the

spaces provided. All working should be shown. For numerical

answers, units should be quoted wherever they are appropriate.

Answer any four questions in section B. Write your answers

on the answer sheets provided. Begin each answer on a freshsheet of paper and arrange your answers in numerical order.

Tie your answer sheets to this question paper.


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Section A [ 40 marks ]

Answerallquestions in this section.

1.(a) The relative atomic mass of an element X is 63.55

(i) Why is the relative atomic mass of X not a whole number ?

[1 mark]

(ii) X contains two isotopes with nucleon number 63 and 65. Given that the masses of63 X and 65X are 62.93 and 64.93 respectively.Calculate the relative abundance of

the isotopes 63 X and 65X.

[3marks]

(iii) If X exist as a monoatomic element,sketch the mass spectrum of X .[2marks]

(b) (i) Write the fundamental particles for each species in the table below.

Species protons neutrons electrons

20 Ne

10

16 O2-8

[3 marks]

(ii)What are the relationship between the two species.

[ 1 mark]


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2(a) The mechanism for the ionization of iodide ion by hydrogen peroxide is as shown below:

H2O2 + I H2O + IO

H+

+ IO

HIO

HIO + H + + I H2 O + I2

(i) Write the overall equation for the reaction above.

............................................................................................................................................................

(ii) What is the rate equation for the oxidation above?

............................................................................................................................................................

(iii)The data obtained from one experiment about the oxidation above is shown below.By assuming that this data is consistent with the mechanism that is suggested,

complete the table below.

Initial rate

(mol dm-3 s-1)

Initial concentration

(mol dm-3

)

H2O2 H+ I

1.0x 10 -42.0x 10 -41.0x 10 -42.0x 10 -4

0.1

............

0.1

0.2

0.1

0.1

0.2

0.1

0.1

0.1

............

0.2

(iv) What is the overall order for the reaction above?

.............................................................................................................................................................

[5 marks]

slow

fast

fast


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(b) The graph below shows the relationship between lg ionization energy and the number ofionizations for all electrons in an atom of X.

(i) How many protons are there in the nucleus of atom X?

.............................................................................................................................................................

(ii) Write the electron configuration for atom X.

.............................................................................................................................................................

(iii) If atom X forms a cation, what is its most probable charge? Give a reason .

............................................................................................................................................................

...........................................................................................................................................................

(iv) Predict the electricity conductivity of element X compared to the other element on

its left in the same peiod of the Periodic Table.

............................................................................................................................................................

[5 marks]

lg

ionizatione

nergy

ionization number


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3.(a) Explain why the reactivity of Group 2 elements in the Periodic Table increases whendescending the group from beryllium to barium.

.............................................................................................................................................................

.............................................................................................................................................................

.

[2 marks]

(b) i. Write a balanced equation for the reaction of the hydrated beryllium ion , [Be(H2O)4]2+

, in

water.

.............................................................................................................................................................

ii. What is the property exhibited by the hydrated beryllium ion in the above reaction?

.............................................................................................................................................................

[2 marks ]

(c) Explain briefly why beryllium forms covalent compounds compared with other elements inthe same group.

.............................................................................................................................................................

.............................................................................................................................................................

[ 2 marks ]

(d) Nitric (V) acid is manufactured from ammonia in the Ostwald process..

i. Name the catalyst used in this reaction.

.

ii. Write equation to show the formation of nitrogen monoxide in the Ostwald process.

iii. Predict qualitatively the conditions of temperature and pressure that will give a maximum

yield of nitrogen monoxide at equlibrium.

[4 marks]


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4.(a) Butanenitrile, CH3CH2CH2CN, is hydrolysed in acidic conditions to yield

compoundA. When compoundA is reacted with phosphorus pentachloride, acompoundB is produced. CompoundB reacts with ethanol to produce a liquid C

which has a sweet smell.

i. Determine the structural formulae for compounds A,B, and C.

A

B

C

ii. Give the IUPAC name for the compound B.

..

iii. Write the chemical equation for the formation of compound C.

.

[ 5 marks](b) Glycine (2-aminoethanoic acid) and alanine (2-aminopropanoic acid) are two simple

amino acids.

i. Draw the structure of the zwiterion of glycine

ii Describe the formation of two possible types of dipeptides from glycine andalanine by giving the equations for the reactions involved. Give the names of

the dipeptides formed.

iii. Explain what happens when alanine reacts with hydrochloric acid. Write the

equation for the reaction involved.

..

[5 marks]


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Section B [ 60 marks ]

Answer anyfour questions in this section.

5. (a) Hunds rule and Aufbau principle are two fundamental principles used in electronicconfiguration of elements.

(i)Hunds Rule states that in a set of degenerate orbitals, the orbitals are each filled

with one electron with parallel spins before pairing occurs.

State the meaning of degenerate orbitals and give example of a set of degenerate

orbitals.

(ii)Using Aufbaus principle, explain how the valence electron configuration for

nitrogen is written.

[ 6 marks ]

(b) Give the electronic configuration of iron in the oxidation state of +2 and +3.

Hence explain why iron(III)compounds are more stable than iron (II) compounds.[ 4 marks ]

(c ) Explain the overlapping of orbitals in ammonia molecule.

[ 5 marks ]

6. (a) What do you understand by dynamic equilibrium? [ 2 marks ]

(b) In an experiment, 0.100 moles of dinitrogen tetraoxide is allowed to dissociate to nitrogen

dioxide in a 1.00 dm3 container at 383 K. The graph of concentrations of both gases

against time is shown below.

(i) Calculate the equilibrium constant, Kc for the above reaction at 383 K.

(ii) Calculate the pressure in the container after the system had achieved equilibrium

at 383 K. [ 8 marks ]


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(c) The graph below shows the percentage of ammonia gas in an equilibrium mixture for the

system N2(g) + 3H2(g) 2NH3(g) at various temperatures and pressures.

Explain the conclusions that can be obtained from the graph above. [5 marks]

7. (a) The ore of aluminium is bauxite.

(i) Briefly describe the extraction of aluminium from pure bauxite.

(ii) Explain the use of aluminium in aircraft construction. [ 7 marks]

(b) Aluminium, silicon,phosphorus and sulphur are Third Period elements in the Periodic

Table. The melting points of the elements are given in the following table.

Element Melting points/0C

Aluminium 660Silicon 1410

Phosphorus 44

Sulphur 119

Explain the melting points of the elements in terms of structure and bonding.

[8 marks]

8. (a) Explain why chlorine is used in the large scale preparation of bromine from sea water

which contains bromide ions. [4 marks]

(b) Explain why iodine is more soluble in potassium iodide solution than in water.Writebalanced equations for the reactions that occur. [4 marks]

How,and under what conditions,does sodium chloride react with concentrated sulphuric

acid ? Write balanced equations for the reactions that occur. [4 marks]

(d) Explain what happens when solid potassium iodide is heated with concentrated sulphuric

acid. [3 marks]

% ammonia in

equilibrium

mixture

0

20 -

40 -

60 -

80 -

100 -

0 2.0 4.0 6.0 8.0 10.0 12.0Pressure, p x 10

4kPa

473 K

673 K

773 K


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9.( a ) Three compounds W, X and Y have the following structures shown below:

W X Y

NH2 CH3 CH2NH2 NH3

( i ) Arrange W, X and Y in ascending order of their basicity.

Explain your answer. [ 5 marks ]

( ii ) W has a pKb value of 9.39. Predict the pKb value of the compound Z shown

below.

Compound Z: NH2

Cl

Explain your answer. [ 4 marks ]

( b ) Nitration of benzene is an electrophilic substitution reaction. Write the reaction

mechanism of the nitration of benzene. In your answer, state the reagents and

conditions of the reaction.

[6 marks ]

10. ( a ) A synthetic polymer R is synthesised from monomers P and Q shown below.

P: HOCH2CH2OH and Q : HO2C CO2H

( i ) Name this synthetic polymer R and draw two repeating units of this polymer.

( ii ) State the type of polymerisation that takes place during the formation ofR and give

one use of R in our daily life.

[5 marks]

( b ) The molecular formulae and some properties of two compounds K and L are given

below. For each compound, identify a functional group which must be present and give

the structural formulae oftwo possible isomers.

( i ) K , C3H8O, gives white fumes of hydrogen chloride with phosphorus pentachloride.

( ii ) L , C3H6O , gives an orange precipitate with 2,4-dinitrophenylhydrazine reagent.

For each pair of isomers K and L, give one chemical test that would enable you to

distinguish between them, stating clearly how each isomer would behave.

[10 marks]

END OF QUESTION PAPER


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No. 7(a) (i) Aluminium metal is extracted by electrolysis

The electrolyte is molten bauxite in sodium hexafluoroaluminate.

The electroyte has aluminium ion and oxide ions.

Anode : 2O2-

--- > O2 + 4e

Cathode : Al3+

+ 3e --- > Al

[5](ii) (Any 2 points)

light

Resistant to corrosionStrong alloy [2]

`(b) aluminium :

A giant metallic structure, strong metallic bonf.

Silicon : giant 3 D covalent structure.Strong covalent bond between silicon atomes.

higher melting point

Phosphorus and sulphur - Both are simple molecules.

Weak van der waals between moleculesSulphur has a stronger intermolecular forces S8 larger than P4 [8]

No 8. (a) chlorine strong oxidation agent

Bromide is oxidized to bromine

E of chlorine is more positive than that of bromine.

Cl2 + 2Br- ---- > 2Cl- + Br2 [4]

(b) iodine forms triodes complex in KI.I2 + I

----- > I3

-

Iodine does not form any complex ions in water.I2 + 2H2O --- > I

- + HIO + H3O+ [4]

(b) HCl is released in cold acidNaCl + H2SO4 NaHSO4 + HCl

If heated more HCl released.

NaHSO4 + NaCl - Na2SO4 + HCl

[4]

(d) Iodide is oxidized to iodine

Purple Iodine is released

Pungent smell of H2S is detected [3]

STPM Trials 2009 Chemistry Paper 2 (Pahang)

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Transcript of STPM Trials 2009 Chemistry Paper 2 (Pahang)