Stpm Chem p1 2011

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Section A

Four suggested answers labelled A, B, C, and D are given fo r each question. Choose one correctanswer.

t Chlorofluorocarbons, CFC, are responsible for the destruction of.ozone in.the stratosphere.I n he stratosphere, theCFCmolecules are fragmented by ultraviolet radiation to producechlorine free radicals, Cl . What is.i:he composition of a 35 Cl free radical?

A

B

cD

Number of proton

35

17

1717

Number of electron Number of neutron

35 35

17 18

18 1817 35

2. Which of the following species will be deflected most in a mass spectrometer?

A J 6 y +B J6y2+c J8y>D J8y2+

3. X andY are two elements in the Periodic Table. The proton number of X is 28, and Y2 + ionis isoelectronic with X. Which of the following electronic configurations is correct?

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A

B

cD

Element/ ion

Xy- -

y 2 '

y2 +

Electronic configuration

ls 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2

ls 2 2s 2 2p 6 3s2 3p6 3d 8 4s 2

ls 2 2s2 2p 6 3s2 3p6 3d 8 4s2

ls 2 2s 2 2p 6 3s 2 3p6 3d 10

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4. The diagram below shows the lines in the visible region of the electromagnetic spectrum o f

the hydrogen atom.

II I I400

J

500Wave length/nm

600 700

Which of the following electronic transitions between energy levels produces the line J?

A D2 __,_ DJB 11 3 - -+ 11]c n3 -- + n2D 114--+ 112

5. Which ofthe following sets of physical properties is that of a transition element?

A

B

cD

Melting point/ C

3'27

650

1539

1410' - - - -

Boiling point 1 C 0

1750

1150

2800

2500

Density/ gcm 3 Ability to condu ctelectricity

11.3 Good

1.7 Good

7.9 Good

2.3 Weak

6. Which of the following sets of elements has the same type of bonding and 1sarranged in ascending order of melting points?

A Cl, S, PB Ge, C,BC Cs, Rb, KD Be, Mg, Ca

7. Which ofthe following species has a bond angle of 109.5?

A N H /

B SF4C XeF4D ICl4.

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8. The following reaction is ftrst order with respect to [P] and zero order with respectto [Q].

P + Q -7 products

If the rate constant doubles for each 10 'C rise in temperature, which of th efollowing sets of conditions will give the greatest rate of reaction? .

ABcD

...... T '[P]/ moldm

0.10.10.30.3

[Q]/ moldm 3

0.20.30.10.1

Temperature/ 'C40302030

9. The reaction of acidified aqueous potassium iodide with hydrogen peroxide is givenby the following equation :-

2r(aq) + H2 02(aq) + 2H+(aq) -7 b(aq) + 2H 2 0(l)

The reaction mechanism is thought to involve the following steps:

H 20 2 + r -7 H2 0 +or (slow)or+ H+ -7 HOI (fast)H O I+ H+ + r -7 12 + H20 (fast)

Which one of the following conclusions cannot be drawn from this information?

A The acid acts as a catalyst.B Th e iodide ion is oxidized by the hydrogen peroxide.C The rate equation for the reaction is; rate= k[H2 0 2] [ I"]D Th e reaction is first order with respect to the iodide ion.

10. The equilibrium constant, Kp for the reaction:

PCls(g) ~ PCh(g) + Clz(g)

is 3.81 x 102 at 600 K and 2.69 x 103 at 700 K. Which of the following statements could bewrong?

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A K, = Kp(RT).B Th e reaction is endothermic.C Th e proportion of PCh in the equilibrium mixture increases with decreasing pressure.D Th e equilibrium amount of reactants and products are not affected by addition of a

catalyst.


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11. The F-F bond in F2 molecule is relatively weak because the lone pairs of electrons onone F.atom repel the lone pair on the other F atom; Kp = 7.83 atm at 1500 K for the reaction . .

)fthe equilibri_umpartial pressure of F 2 molecules at 1500 K is 0.200 atm, what percentage .of the F 2 molecules is dissociated at 1500 K?

A 75.8%B 79.7%c 86.2%D 88.7%

12. The following reaction equations may be Arrhenius, Bronsted-Lowry, and/or Lewis acidbase reactions. Which of the following reactions is a Bronsted-Lowry and a Lewis acidbase reaction?

A A!Ch + Cl' -7 AICI4.B Ag+ + 2NHJ -7 Ag(NH3)2+C H,S04 + NH3 -7 HS04. + N H /D Al(OH)J + 3HNOJ -7 Atl+ + 3H,O + 3No3

13. A saturated solution ofMg(OHh in water at room temperature has pH= 10.35. Calculatethe solubility product, K,p for Mg(OH) 2 at room temperature.[Ionic product of water at 25 C, Kw = 1.0 x 10' 14 mo12 dm-6]

A 1.12xl0 11

B 4.49 X 10'11

C 5.61 X 10' 12

D 2.84 X 10 ' 13

14. Calculate the concentrations o f N H / and NH 3 and the pH of a solution prepared by mixing20.0 g of NaOH and 500 cm 3 of 1.5 mol dm 3 NH 4CL Assume that the volume remainsconstant.

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[Base dissociation constant ofNH 3, Kb = 1.8 x I o5 mol dm-3; relative atomic masses: Na =

23, 0 = 16, H = 1.)

A

BcD

[NH/]0.500.751.0

0.50

[NH 3] pH1.0 9.56

0.50 l l .51.0 9.26

0.50 9.26


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15. In a steam distillation exper iment to obtain diphenylamine, C 12 H 11 N, the total vapourpressure reaches 101.0 kPa at 99.4 C. At this temperature the vapour pressure of water is99.2 kPa. Calculate the minimum mass of steam required to obtain 100 g o fdiphenylamine. [Relative atomic masses: C = 12, H = 1, N = 14.]

A ;587 gB 666 gc 678 gD 866 g

16. Separate samples of three amino acids, X, Y and Z, were spotted on the base line of a thinlayer chromatography sheet. Th e chromatogram produced using a particular mobile phaseis shown below. The Rr values of known amino acids are given in a separate table asshown below.

Solvent front

Origin L======:.J

6

0

Amino acidAlanineArganineIsoleucineProline

TaurineValine

Which of the following sets below correspond to X, Y and Z?

X y zA Isoleucine Alanine ValineB Proline Taurine Arganinec Isoleucine Taurine AlanineD Proline Taurine Arganine

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Rr value0.560.610.820.89

0.340.75


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17. The table below shows the standard electrode potentials for several half-cell reactions

Half-cell reaction E8 IV Half-cell reaction E 8 / V ....

.

Ba-+ + 2 e - ~Ba -2 .90 CrJ+ + 3 e - ~Cr. ..

c 0.74co-++ 2e ~ C o - 0.28 Pb0 2 + H ' + 2 e - ~Pb_+ +2H,O - +1A7

.

CoJ++e ~ c o - ~ + 1.82... ------ - -""--

Which of the following redox reactions will give the highest value of e.m.f?

A Co 2 + + Ba ~ Co + Ba 2+B 2C r 3+ + 3B a ~ 2Cr + 3Ba 2+C 2Co 3+ + Ba ~ Ba 2+ + 2Co 2+D 2Co 3+ + Pb 2+ + 2H 20 ~ 2Co

2+ + Pb0 2 + 4H+

18. In the electrolysis of dilute sulphuric acid, calculate the quantity of electricity in Faradaysthat will be required to produce 112 cm 3 of gas at the anode measured at s.t.p?[I mole of gas at s.t.p occupies 22.4 dm 3]

A F/200B F/100C F/50D F/25

19. Which of the following reaction equations involves the enthalpy change of formation?

A 2H(g) + '/, 02(g) ~ H20(g)B CO(g) + y, 02(g) ~ C02(g)C 2N(g) + 3H 2(g) ~ 2NH 3(g)D 2C(s) + 3H2(g) ~ C2H6(g)

20. Which of the following variation in properties is caused by the increase in th e atomic orionic size of the Group 2 elements when going down the group?

A the decreasing basicity of the oxidesB the increasing solubility of the sulphatesC the decreasing thermal stability of the carbonatesD the increasing reactivity of the elements towards water



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21. Which of the following is no t true of aluminium chloride?

A Anhydrous aluminium chloride can act as a Lewis acid.B In the vapour state, aluminium chloride consists of the Al 3+ and cr ions ..C At room conditions, aluminium chloride exists in the dim eric form, AbCl 6D Aluminium chloride can be prepared by the reaction o f aluminium with hydrogen

chloride gas,

22. Which of the following best explains why silicon tetrachloride and not carbon tetrachlorideis hydrolysed by water?

A The C-Cl bond is stronger than the Si-Cl bond.B The silicon atom is bigger than the carbon atom.C Carbon can undergo catenation whereas silicon cannotD Silicon can use available d orbitals to expand its valency, whereas carbon cannot

Lead (IV) chloride decomposes to lead(Il) chloride when warmed. What can be deducedfrom this information alone?

A Lead is a metaLB Lead (IV) chloride is readily hydrolysed by cold water.C Lead (IV) chloride is covalent whereas lead(Il) chloride is ionic.D The +2 oxidation state oflead is more stable than the +4 oxidation state.

24. The method used in the industrial preparation of nitrogen gas is

A decomposition o f ammonia in airB Fractional distillation of liquefied airC thermal decomposition of ammonium nitrateD thermal decomposition of ammonium chromate

25. Which of the following properties increases when going down Group 17?

A the oxidising ability ofthe halogenB the electronegativity of the halogenC the lattice energy of the sodium halideD the strength of the halide ion as a reducing agent

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26. Which of the following statements about the complex [Co(H 2NCH 2 CH 2NH 2)3] 3+ is not .correct?

A the complex has an octahedral shape.B the ligand in the complex is bidentate.C the oxidation state of cobalt in the complex is +3.D the coordination number of cobalt in the complex is 3.

27. Consider the species in the following equation:-

Which of the following statements is not correct?[Proton Number ofTi = 22]

A water acts as a Lewis base.B the complex ions are octahedral in shape.C the [Ti(H 20) 6]

3+ ion can act as a Bronsted-Lowry acid.D the electronic configurations of the titanium ion is !s 22s 22p 63s 23p 64s 1

28. How many stereo isomers does compound X have?

/O H

@ - c H = C H C H ( O H ) C H l

X

A 0 B 2 c 4

29. Acetaminophene is a drug used in headache remedies

H CH3I I

H O - @ - N - - C = O acetaminophene

Which of the foilowing statements about acetaminophene is true?

A it is soluble in waterB it reacts with PCI 5 to give dense white fumesC if forms a yellow precipitate with alkaline iodine solution

D 6

D it can be synthesised from the reaction of I - b N - - O H and CH 3COCI

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30. Consider the four compounds below labelled I, II, Il l and IV.

Cl COOH CH3 Cl

0 0 ICHcOH OH OH OHl l l l i l IV

Which of the following answers give the correct sequence of the above compounds indecreasing order o f acidity?

A II, IV, ll l and IB II, Ill, IV, IC I, Ill, IV, IID Ill, I, IV, II

31. P, C 3H 7N is a liquid that dissolves readily in dilute hydrochloric acid. Q, C 2H 5NO is asolid that gives an alkaline gas when heated with aqueous sodium hydroxide. Which of th efollowing pairs of compounds could P and Q be?

ABcD

pCH2=CHNH(CH3)CH 3CH=CHNH 2CH3NHCH=CH2

H' ;:--......_____

I /( :H(NH2)2H i : ~ /

QCH3CONH2H2NCH2CHOCH 3CH=NOH

H2 ~ ~ C H ( O H )

H N /

32. Part of the structure of a polymer is shown below:-

Which of the following statements about the above polymer is correct?

A it is resistant to alkaline hydrolysis.B it is both a polyester and a poly amideC it reacts with HC N in the presence of a trace of acidD it can be made from ClCO(CH 2 ) 4COCl and HOCH2(CH 2)2CH 2NH 2



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33. The polymer whose repeat unit is shown below occurs in bacteria as cell storage materia l:- ..

CH3 H 0

I I II- 0 - C - C - C -

1 IH H

This polymer can be formed by the polymerisation of

0II

A CH 3C H - C - O H

IOH

B CH 3 CH=CH-COOHI

OH

C CH 3CH--CH 2- C O C l

IOH

34. A compound R has all the following properties:-(i) it is neutral(ii) it gives an orange precipitate with 2,4 dinitrophenylhydrazine(iii) it forms a yellow precipitate with aqueous iodine in sodium hydroxide solut ion

Whichofthe

following couldbe R?

A g 1 CCH1 B ; Q ( HH 3C COCH 3

c i f H : O H D ~ C H 2 0 H

CH2CHO COCH 3

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35. In the reaction scheme below, one of the steps is incorrectly represented. There could .be anerror in specifying the reactants, the products or the reagents used. Which is the incorrectlyrepresented step'!

LiAIH4CH 3CN ~ CH,CH2NH2

H20/I- t J tep 2CH,C02H

A step I

Step 1

Step 3

B step 2

Step 4

C step 3 D step 4

36. Which of the following compounds can be used to prepare a stable solution of a diazoniumsalt at 5C

..

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38. Compound S, C4H 80 2 is resistant to oxidation. When treated with sodium,one mole of Sliberates 0.5 mol of hydrogen gas. Sis

A CH1CH2 C02CH1B CI-1JCH2CH2C02HC CH1CH2COCH20HD CHJCH(OH)CI-hCHO

39. It has been estimated that every atom of chlorine generated from a chlorofluorocarbon inthe strastophere, one hundred thousand molecules of ozone may be destroyed. Which ofthe following statements about the chlorine atoms given below is correct?

A they initiate the formation of oxygen free radicalsB they are regenerated in a chain propagation reaction.C they remove oxygen formed by the reaction 20 3 ~ 3 0 2D they achieve high activation energy by absorbing ultra violet light

40. The compound E below reacts with aqueous sodium hydroxide when heated. What type ofreaction does E undergo?

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C I - - @ - - C H 2 C H 2 C l

E

A electrophilic additionB electrophilic substitutionC free radical substitutionD nucleophilic substitution

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Section B

For each o ft he questions in this section one or more o ft he three numbered statements 1 to 3may be correct. Decide whether each o ft he statements is or is nor correct. The responses A to Dshould be selected on the basis o f he following.

A B c D1 only is correct. 1 and 2 only are 2 and 3 only are 1, 2, and 3 are

correct. correct. correct.

41. A group of mountain climbers discovered that water boils at a lower temperature at th e topof a mountain. Which statement(s) is/are t r u e ~

Atthe mountain top, the pressure

islow and water will only boil when the

vapour

pressure equals the prevailing pressure.2 At lower temperature, the kinetic energy of molecules is low, thus water boil at lower

temperature.3 At lower temperature, fewer molecules vaporise and thus boiling point of water

drops

42 The rate equation for the reactionF2(g) + 2Cl0 2(g) ~ 2FCl02(g)

at 500C is given by: Rate of reaction= k [F 2][CI0 2]0

Which statement(s) about the rate equation is/are correct?

The overall order of reaction is 1.2 The rate constant depends on temperature.3 The unit of the rate constant is mor 1s 1

43. Several standard redox potential values are given in the table below:

Redox reactions E 8 / V

Fe-+ (aq) + 2e ;:==:::': Fe(s) -0.44Fe'+ (aq) + e ;:==:::': Fe-+ (aq) + 0.77HN0 2 (aq) + H+ (aq) + e ;:==:::': NO(g) + H 20(l) + 0.99Sn 4+ (aq) + 2e ~ sn-+ (aq) + 0.15

Which of the following will oxidise Sn2

+ ions to Sn4

+ ions under standard conditions?

1 HN0 2 (aq)2 Fe 3+ (aq)3 Fe 2+ (aq)



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~ ~

A B c DI only is correct. 1 and 2 only are 2 and 3 only are 1, 2, and 3 are

correct. correct.correct.

44. Three standard redox potential values are given in the table below:

Redox reactions E 8 IVco'+ (aq) + e ~ co+ (aq) + 1.81Cr'+ (aq) + e ~ Cr + (aq) 1-041 - -

i'+ (aq) + e ~ Ti"+ (aq) -0.37

Which of the following redox reaction(s) can occur under standard conditions0

Co3+ (aq) + Cr

2+ (aq) -7 Co

2+ (aq) + Crh (aq)

2 Cr 3+ (aq) + Ti"+ (aq) -7 Cr 2 + (aq) + Ti 3+ (aq)3 Ti 3+ (aq) + Co 2 + (aq) -7 Ti 2+ (aq) + Co 3+ (aq)

45. The diagram below shows the Born-Haber cycle for the formation of potassium bromide

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K' (g) + e + Br(g)

j K'(g) + e + Y, Br2(g)t K+ (g) + B( (

- ~ - - - - - - - - - - - - - - - - - - - - - - -

K(g) + y, Br2(g)

g)

622

510

280

90

K(s) + ~ S Br2 (g)0

KBr(s)

- 392

Which of the followings enthalpy changes can be correct(v deduced from th e aboveBorn-Haber cycle?

l Electron affinity of bromine is - 34 2 kJ mor 1

2 The lattice energy of potassium bromide i s - 672 kJ mor 1

3 The enthalpy change for the reaction Br 2(g) -7 2Br(g) i s - 224 kJ


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A B c D1 only is correct. 1 and 2 only are 2 and 3 only are 1, 2, and 3are

correct. correct. correct.

46. P 40 10 is a solid while P406 is a liquid. Which of the following statement(s) can be used toexplain this observation?

P4010 is ionic while P406 is covalent.2 P40 10 has more electrons than P4 0 63 The size ofP,0 10 is bigger than that of P40 6

47. Which of the following reaction(s) of ammonia involve(s) the lone pair electrons on thenitrogen atom?

1 Nl-b(g) + HCl(g) -'7 NH4Cl(s)2 NH 3(g) + CH 3l(g) -'7 CH3NH3+r(s)3 2NH 3(l ) + 2Na(s) -'7 2NaNH 2 (s) + l-lz(g)

48. Many sunburn ointments contain benzocaine which rlieves the pain caused by sunburn. Itcan be made in the laboratory using the following reaction scheme. Which of the followingreagents in these steps is/are correct ?

CH3

COOH

~ ~ ~ - s t e p _ 2 - - +

step I requires hot acidified KMn0 4 solution2 step 2 requires refluxing with acid catalysed ethanol3 step 3 requires the reagent lithium tetrahydridoaluminate (LiAlH 4 )

49. Which of the following test(s) below can be used separately to distinguish between thefollowing hydroxy compounds X andY ?

H O - - C H J (X) H O C H ( C H J ) - < Q > - O H (Y)

adding hot aqueous alkaline iodine2 adding aqueous bromine solution3 adding hot acidified potassium manganate(Vll ) solution



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AB

cD

1 only is correct. 1 and 2 only are 2 and 3 only are 1, 2, and 3 arecorrect. correct. correct .

. .

50. Methadone, a narcotic analgesic can be used as a substitute for heroin

From the structure of Methadone above, it can be concluded that Methadone:-

1 gives nitrogen gas with cold nitrous acid2 turns the red litmus solution to blue3 gives an orange precipitate when heated with 2,4 dinitrophenylhydrazine

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