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PEPERIKSAAN PERCUBAAN SETARA STPM

NEGERI SEMBILAN DARUL KHUSUSTAHUN 2011 '

Instructions to candidates:

Answer all the questions m Section A in the spaces

provided.

All working must be shown. For numerical answers,units must be quoted wherever they are appropriate.

Answer any four questions from Section B. For thissection. write your answer on the answer sheetsprovided. Begin each answer on a fresh sheet of paper.and arrange your answers in numerical order. Tie youranswer sheets to this booklet.

Answers may be written in either Malay or English.

A Data Booklet is provided.

For examtnerls use

only1

2

3

4

5

6

7

8

9

10

TOTAL

This question paper has 12 printed pagese;:, .Jabatan Pelajaran Negeri Sembi ian 20 I I

Percubaan STPM 962/2 [Turn over*This question paper is CONFIDENTIAL until the examination is over. CONFIDENTikL*

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Section A [40 marks]

Answer all c;uesriom inlhis seclion

1 (aJ The structural formula s:10wn below is that o f compound X Compound X shows .th e incomplete structure of Vitamin C .

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H

HI

0 ~ /p-cI \

O - H

c c - o\ ~ /H 0

Compound X

(i) Complete the Lewis electron-dot structure o f compound X in the diagramabove.

(ii) Describe the type o f hybridization o f each carbon atom in the compound X.

[3 marks]

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(b) (i ) Classif) the type of bond that exists in each of the following substances. Thenwrite the formula of the substance(sl that has the type of bond as stated in Table l .

Table 1

Type of bond Substance(s)

lonic

Non-polar covalent

Polar covalent

[3 marks]

(ii) Arrange all the polar covalent substances from Table 1 in the order ofincreasing bond polarity.

[1 mark]

(c) Predic t the molecular shape oft11e follo\\ing species and state the value of the bondangle/ angles

Shape Bond ang1e(s)

?Cis

PCk"ion

L _ _ _ _c_16_-_io_n_ _ ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ - - - - [3 marks]

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2 (a ) The solubility product. K, 0 . of magnesium hydroxide is 2.5 xI olc mol3dn{'.

(i) Write alr expression for the K,r of magnesium hydroxide.

(ii) Lise the value of Ksp given above to calculate the concentration of thesaturated magnesium hydroxide solution.

(iii) Would magnesium hydroxide be more or less soluble in 0.1 mol ctm 3

magnesium sulphate solution than in water? Explain your answer.

[ J mark]

[J mark]

[J mark]

(b) A buffer solution is prepared by dissolving solid ammonium chloride in 250 cm 3 ofC!.20 mol dm- 3 ammonia solution. Calculate the mass of ammonium chloride thatneeds to be added to produce a solution with pH= 9 0.[Kb of ammonia= 1.75 x I o- 5 mol dm- 3]

[3 marks]

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(c) A mixture of liquid P and Q obeys Raoulfs Law. At the temperature 373 K, thevapour pressures of pure A and pure Bare 56 kPa and 34 kPa respeeiively. Amixture. containing 70% of A and 30% ofB is fi-actionally distilled. The mixtureboils at a temperature of 373 K.

(i) What is the total pressure of the boiling mixture at 3 7 3 K ~ '

[2 marks]

(ii) Calculate the composition of the first vapour formed in the fractionating

column.

[2 marks]

3 (a) The table below shows the structures of the elements in Period 3 of the PeriodicTable from Nato Cl

1 Elements IN a~ t r u c t u r e

i MoI "'

IAIGiant metallic structure

(i) What is the structure for silicon?

I Si :p Is I ClSimple molecular

[J mark]

(ii) The elements of Period 3 trom Nato S burn in oxygen when heated to formtheir respective oxides. Stat

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(iii) Draw the Lewis diagram for SO,

[ 1 mark](b) The nitrates of Group2 elements decompose on heating.

(i) Write the chemical equation for the decomposition of magnesium nitrate.

'[1 mark]

(ii) What is observed when magnesium nitrate is heated strongly?

[1 mark]

(c) How does the solubility of the sulphates of Group 2 elements change when movingdown the group? Explain your answer.

[3 marks]

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4 Compound Y has the folowing structural lormula:-

(a) One ofthefutiCtional gl'oupsp'fesent in Y has basic properties. ldentify thisfunctional group and write an equation for th e reaction ofY with dilutehydrochloric acid at room temperature

[2 marks]

(b) What are the other functional groups that are present in compound Y?

[J mark]

(c) Give the structural formula( e) for the organic product(sl formed in th e reactions

o f compound Y with

(i) ho t aqueous sodium hydroxide

(ii) lithium tetrahydridoaluminate, L i A l ~in ether.

(iii) sodium metal at room temperature

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(iv) aluminium oxide with heating.

[5 marks]

(d) Compound Y can be formed by the reaction between an amino acid with an acylchloride

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(iJ Write an equation for the above reaction to form Y.

(ii) Compound Za n isomer of Y can also be formed in the above reaction. Drawthe structural formula of compound Z

[2 marks]

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Section B [ 6(1 marks]

Answer anlj(;ur qucsliom in rhis sec/ion

5. (a) When 0.269 g of a dibase (diproticJ organic acid A is vapourised at 120 C into a 1O:Odm 3

vesseL the pressure measured is 1.00 x 10' Pa.Calculate the relative molecular mass lv1, for acid A. Predict with reasons whether acid A islikely to behave ideally in the conditions given above.

[5 marks]

(b) The mass spectrum of acid A contains peaks at m/e values of 17. 28, 45, 56 and amaximum value of 90. Identify acid A and the species which give rise to these peaks.

[4 marks]

(c) Explain the following observations in tem1s of structure and bonchng.(i) Trimethylamine. (CH 3) 3N has a lower boiling point than dimethylamine,(CH3)2NH.(ii) The relative molecular mass of methanoic acid. HCOOH as determined in anaqueous solvent (water) is 46 bm is doubled when determined in a non-aqueous solvent(benzene).

[6 marks]

6. (a) Defme the term electronegativity.[1 mark]

(b) State and explain the trend in electronegativity across Period 3 from sodium tochlorine.

[4 marks]

(c) Explain why the atomic radius of an element decreases across Period 2 from lithium tofluorine.

[2 marks]

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(d) A student sets up the apparatus below to carry out an electrolysis experiment:

Copper rod Y ' . ~ i r h

siker impurities e,-, Lf - - -

-

u:=-

- - -- - -

I I I

-

~ -. . . - - - + Brass photo frame~

- - - -- - ' - - - - - - - Aqueous

- - - - I- - - - - I

I

copper(II) sulphate solution

By referring to the Data Booklet, describe and explain what happens at the anode. cathodeand the electrolyte after a few hours

[8 marks]

7. (a) (i) \Vhat do you tmderstand by "anodizing" of a l u m i n i u m ~(ii) Describe the method used to catTY out this process. Explain the chemistryinvolved with the aid of balanced equations.

[7 marks]

(b) State and explain the thermal stability of Group 14 tetrachlorides from carbon to lead.[4 marks]

(c) (i) Name one tetrachloride of Group 14 that does not react with water and explainwhy.(ii) Name one tetrachloride of Group 14 that reacts with water and vvrite an equationfor that reaction.

[4marks]

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8. (a) Explain why the reaction between sodium halides with concentrated sulphuric acid can beused to prepare bromine but not chlorine.

[4 marks]

(b) The elements scandium. manganese and zinc are first row d-hlock elements of thePeriodic Table.(iJ Write the electronic configurations for the following ions: Sc 3+, Mn:+ and Zn 2+.(ii) Vv'hich of the above ions is/are colourless" Explain why.

[5 marks]

(c) A typical property of transitional elements is their ability to form complexes. A complexof chromium has the formula [Cr(NH 3)6]:h

(i) Explain how the [Cr(NH 3J,J'" ion can be prepared from aqueous chromium (III)chloride solution.(ii) Explain wh) Cr"'. ions have a great tendency to form such complexes.

(iii) Another complex of chromium has the formula [CrCl 2 (NH 3) 4f . Draw thestructural fommlae for the two isomers of this complex

[6marks]

9. (a) 1,4-dichlorobutane was refluxed W"ith ethanolic sodium hydroxide for a few hours to forma single organic compound, X. X then reacts with (HOOC)CH=C(CN)COOH to form thepolymer Y.

(i) Name tbe reaction that took place to form X.(ii) Write a reaction equation for (i).(iii) Name the type of polymerisation involved and draw a repeating unit for thepolymer Y.

[ 4 marks]

(b) Both toluene (methylbenzene) and 2-methylpropene can be chlorinated by differentmechanisms.

(i) Outline the mechanism for the chlorination of toluene using anhydrous iron(III)chloride as a catalyst.(ii) Name and outline the mechanism for the chlorination of 2-methylpropene.

[7 marks]

(c) Compare the acidity of the compounds, A and B below. Explain your reasoning.

Itl. - - '

iCH,A.

962/2

OH

IIi : : : ~ ~ l

, ~ /

- - , l / ~

NO ,

B

'This question paper is CONFIDENTIAL until the examination is over.

[4 marks]

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