962/1 September 2008 1 j 45 min PEPERIKSAAN PERCUBAAN SIJIL TINGGI PERSEKOLAHAN MALAYSIA 2008 CHEMISTRY PAPER 1 One hour and forty-five minutes Instructions to candidates: DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO. There are fifty questions in this paper. For each question, four suggested answers are given. Choose one correct answer and indicate it on the multiple-choice answer sheet provided. Read the instructions on the multiple-choice answer sheet very carefully. Answer all questions. Marks will not be deducted for wrong answers. Arahan kepada calon: JANGAN BUKA BUKU SOALAN INI SEHINGGA ANDA DIBENARKAN BERBUAT DEMIKIAN. Ada lima puiuh soalan d a l a m kertas ini. Bagi setiap soalan, empat cadangan jawapan diberikan. Pilih satu jawapan yang betul dan tandakan jawapan itu pada helaian jawapan aneka pilihan yang dibekalkan.Baca arahan pada helaian jawapan aneka pilihan itu dengan teliti. Jawab semua soalan. Markah tidak akan ditolak bagi jawapan yang salah. This question paper consists of 12 printed pages and blank page. [Turn over (Lihat sebelah) Pahang Trial CONFIDENTIAL* STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL Section A Four suggested answers labeled A, B, C and D are given for each question in this section. Choose one correct answer. 1. Which one of the following pairs of atoms or ions contains the same number of neutrons? A 14C and 12C C 23Na+ and 24Mg2+ B 19F - and 20Ne D 32S and 27Al 2. A sample of magnesium contains traces of magnesium oxide. When the sample is added to 17.6 cm3 of 2.5 mol dm-3 hydrochloric acid, 448 cm3 of hydrogen at s.t.p. are released. What is the mass of magnesium oxide in the sample? [ Ar : Mg,24 ;O,16; Molar volume at s.t.p = 22.4 dm3 ] A 0.08 g C 0.16 g B 0.12 g D 0.24 g 3. Hydrogen peroxide undergoes catalytic decomposition according to the equation Pt 2H2O2(l) 2H2O(l) + O2(g) Calculate the volume of oxygen liberated (at s.t.p.) when 1.0 dm3 of 0.50 mol dm-3 hydrogen peroxide undergoes catalytic decomposition. [Molar volume at s.t.p = 22.4 dm3 ] A 5.60 dm3 C 0.16 dm-3 B 11.20 dm3 D 0.33 dm-3 4. The first seven successive ionisation energies (in kJ mol- ) for four elements are given below. Which one could be that of a Group 17 element? A 580, 1800, 2700, 11 600, 14 800, 18 400, 23 300 B 1010, 1900, 2900, 5000, 6300, 21 300, 25 400 C 1140, 2100, 3500, 4800, 5800, 8500, 9900 D 1000, 2300, 3400, 4600, 7000, 8500, 27 100 5. The shape of the molecule SF6 is best described as A planar. C hexagonal. B octahedral. D pyramidal. Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 6. The phase diagram for a pure substance, X, is shown in Figure 1. The atmospheric pressure is 101.3 kPa. Figure 1 Which of the following statements is correct? A X is a solid at s.t.p. B The minimum pressure required to liquefy vapour X is 200 kPa. C The melting point of X increases as the pressure decreases. D Point Q is the critical point for X 7. The boiling point of methane is higher than that of neon. Which statement best explains this fact? [H = 1; C = 12; Ne = 20] A Methane is a polar molecule, but neon is not. B Methane molecules form hydrogen bonds but not neon molecules. C The intermolecular forces between molecules is stronger in methane than in neon. D A methane molecule has a more electrons than a neon molecule. 8. Combustion of ethanol in pure oxygen is faster than in air because A oxygen is a catalyst for the combustion process B oxygen lowers the activation energy C the concentration of oxygen is higher D nitrogen from the air hinders the combustion process. Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 9. The acid catalysed reaction between propanon and iodine is: H+ CH3COCH3 + I2 CH2ICOCH3 + HI The result of an experiment is shown in Figure 2 below: Figure 2 From this it can be concluded that A the acid is not involved in the reaction. B it is a third order reaction overall. C the rate of reaction does not depend on the concentration of iodine. D the rate-determining step involves only iodine. 10. 50.0 cm3 of an aqueous solution containing 12.0g of phenylamine is shaken with two successive volumes of ether, each of 25.0cm3 . The distribution coefficient of phenylamine between ether and water is 5.0. Calculate the amount of phenylamine extracted. A 11.02g C 8.07g B 10.72g D 15.80g 11 A solution which contains M and N is an ideal solution. The phase diagram of the mixture M and N at temperature T is as follows. Which of the following statements is true of the solution which contains M and N? A Mixture y boils at temperature T. B Mixture x is a liquid at 1.0 atm. C Mixture z exists as vapour at 1.0 atm. D At temperature Pahang T, the vapour composition of mixture Trial y contains more M. STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 12 The proton numbers of four transition elements V, Cr, Fe and Co are shown in the table below. Transition element V Cr Fe Co Proton number 23 24 26 27 Which of the following ions of transition elements has two unpaired electrons? A Cr2+ B Co2+ C V3+ D Fe3+ 13 The industrial process for the manufacture of ammonia is represented by the equation below: N2(g) + 3H2(g) 2NH3(g) ∆ H = -92 kJ Which of the following can be deduced for the following reaction: 2NH3(g) N2(g) + 3H2(g) A The reaction is exothermic B Cataylst will increase the value of the equilibrium constant. C The equilibrium constant increases as temperature decreases. D The production of nitrogen increases with decreasing pressure. 14 In an acid-base titration, a 1.0 mol dm-3 solution of a base is added to a 1.0 mol dm-3 solution of an acid. The graph below shows the variation of pH value of the solution with the volume of the base added. What are the acid and base used in the titration which produced the above graph? Acid Base A HNO3 KOH B HCl NH3 C CH3COOH NH3 D CH3COOH NaOH 15 Silver sulphate, Ag2SO4, and strontium sulphate, SrSO4 are added to water. Which of the statements is true regarding the saturated solution obtained? [Solubility product, Ksp: Ag2SO4 = 1.5 x 10-5 mol3 dm-9 and SrSO4 = 2.8 x 10-7 1.5 x 10-7 mol2 dm-6 at 298 K] A SrSO4 is more soluble than Ag2SO4. B The sulphate ions in the saturated solution come from SrSO4. C The concentration of the sulphate ions from Ag2SO4 can be ignored. D Addition of a little silver nitrate will decrease the solubility of Ag2SO4. Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 16 The diagram for the Daniell cell is shown below. Which of the following statements regarding the Daniell cell is correct? A The Zn2+ ions are attracted to the zinc electrode. B The Cu2+ ions are attracted to the zinc electrode. C The K+ ions are attracted to the copper electrode. D The SO4 2- ions are attracted to the copper electrode. 17 A molten compound consisting elements X and Y is electrolysed using a current of 1.00 A for 1 930 minutes. 2.07 g of X is formed at the cathode and 1.60 g of Y is formed at the anode., Which of the following is the correct empirical formula of the compound? [Relative atomic mass: X = 207, Y = 80, Faraday’s constant = 96 500 C mol-1] A XY B XY2 C X2Y D X2Y2 18 Which of the following pairs of substances is used in the industrial production of chlorine by electrolysis? A Platinum anode and dilute sodium chloride B Platinum anode and concentrated sodium chloride C Carbon anode and concentrated sodium chloride D Carbon anode and molten sodium chloride 19 The diagram below shows the Born-Haber cycle for the formation of sodium fluoride. What is the electron affinity, in kJ mol-1, of chlorine? A -246 B -275 C -328 D -820 Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 20 Which of the following elements from Period 3 (sodium to chlorine) in the Periodic Table forms an oxide with the highest oxidation number? A. Silicon B. Phosphorous C. Sulphur D.Chlorine 21. Which of the following nitrates of Group 2 elements has the highest thermal stability? A. Barium nitrate B. Beryllium nitrate C. Calcium nitrate D. Magnesium nitrate. 22. Aluminium has an external oxide layer that prevents it from corrosion. The oxide layer can be removed by solution A. sodium hydroxide B. sodium chloride C. nitric acid D. zinc sulphate 23. Which of the following statements is true regarding the oxides of the elements in Period 3 ( sodium to chlorine ) of the Periodic Table ? A. Sodium oxide is the strongest base because sodium is the most electropositive element in Period 3 B. Going across Period 3, the properties of the oxides changes from base to acids because the bond between the element and oxygen gets stronger C. Aluminium oxide is amphoteric because it is in Group 13 D. Oxide of phosphorus forms the strongest acid because it is the most soluble in water. 24. The following table shows the lattice energy and the hydration energy of three sulphate salts X,Y and Z for three elements in Group 2 of the Periodic Table. Sulphate salts Lattice energy/kJ mol-1 Hydration energy/kJ mol-1 X -2489 -1650 Y -2374 -1360 Z -2484 -1480 Which of the following sulphate salts are arranged according to solubility in descending order? A X,Y,Z B. X,Z,Y C. Y,Z,X D. Z,X,Y Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 25. Which of the following statements is true regarding tin when compared to lead? A. Its dioxide is basic B. Its tetrachloride is less stable C. It is a more reactive element. D. It is more stable in the oxidation state of +4 26. Transition metals and their compounds are used as catalyst in industry.Which of the following pairs of industrial process and catalyst is not true? Industrial process Catalyst A. Haber Process CuO B. Contact Process V2O5 C. Manufacture of nitric acid Pt D. Manufacture of margarine Ni 27. Which of the series of oxides shows increasing melting point? A. Cl2O7 , Al2O3, SO3,SiO2 B. SO3, Cl2O7, SiO2,Al2O3 C. SO3, Cl2O7, ,Al2O3, SiO2 D. SiO2,Al2O3,Cl2O7,SO3 28. The oxide of metal L is soluble in aqueous sodium hydroxide.This oxide is also soluble in dilute nitric acid and and when aqueous sodium chloride is added to the solution formed,a white precipitate is produced.The oxide of L could be A. Al2O3 B. Fe2O3 C. SnO D. PbO 29. What is the drying agent used to obtain ethanol from distilled ethanol? A. Calcium B. Calcium oxide C. Calcium chloride D. Concentrated hydrochloric acid. 30. When using phenolphthalein as indicator,the volume of 0.1 mol dm-3 aqueous potassium hydroxide required to neutralise 100 cm3 of 0.1 mol dm-3 aqueous ethanedioic acid is A. 200 cm3 B. 150 cm3 C. 100 cm3 D. 50 cm3 Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 31. Which of the following compounds is an amine? A C2H5OH C CH3COCH3 B CH3NH2 D CH3CHO 32 Which one of the following compounds will react with its own oxidation product to give a fruity smell liquid? A Ethene C Propan-1-ol B Propane D Propan-2-ol 33 A compound gives a positive iodoform test, decolourises acidic potassium manganate(VII) solution at room temperature and reacts with phosphorus pentachloride to give off hydrogen chloride gas. The compound could be A Propanone C Ethanol B 2-ethylpropan-1-ol D Cyclohexanone 34 When methylmagnesium iodide is reacted with methanal and the product formed is hydrolysed, the resulting organic product is A CH3CH(OH)CH3 C CH3COCH3 B CH3CH2OH D CH3COOH 35 Which of the following in aqueous solution of equal concentrations has the lowest pH? A Chloroethanoic acid B Dichloroethanoic acid C Ethanoic acid D Phenol 36 Which of the following is formed when methylamine,CH3NH2, is treated with excess iodomethane? A (CH3)2NH C (CH3)3 +NHI- B (CH3)3N D (CH3)4 +NI37 What is the formula of the product formed when a compound with the formula CH3O NH2 reacts with ethanoylchloride? A CH3O NHCOCH3 B CH 3 CO CH 2 NH2 NH2 C CH3O COCH3 D CH 3 CO CH 2 NHCOCH3 Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 38 Which of the following reagents will give the same reaction with phenol and phenylamine? A HNO2(aq) C HCl(aq) B NaOH(aq) D Br2(aq) 39 Which of the following pairs of compounds will react to form a polymer? A HO(CH3)6Cl and H2N(CH2)6COOH B H2N(CH2)6NH2 and HOOC(CH2)6COOH C CH 3 (CH2)3 COCl and CH 3(CH2)5 COOH D HO(CH2)6NH2 and HO(CH2)6COOH 40 Which of the following has hydrogen bonds between its polymer chains? A Poly(propene) B Nylon 6,10 C Poly(phenylethene) D Polyester Section B For each of the questions in his section, one or more of the three numbered statements 1 to 3 may be correct. The responses A to D should be selected on the basis of the following. A B C D 1 only is correct. 1 and 2 only are correct. 2 and 3 only are correct. 1, 2 and 3 only are correct. 41. Sodium iodide crystals are easily broken up into pieces. Which of the following statements explains this observation? 1 The particles in the crystals are arranged in a regular lattice. 2 The particles in the crystals are held by electrostatic forces. 3 The particles in the crystals are separated by large distances. 42. The number of orbitals of a principal quantum number is dependent on the type of subshell. Which of the following statements about the s, p and d orbitals of principal quantum numbers 1,2 and 3 are true? 1 Each s orbital can hold a minimum of two electrons. 2 The filling of d orbitals produces a series of transition elements. 3 The s orbital has a lower energy than the p orbital with the same principal quantum number. Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL A B C D 1 only is correct. 1 and 2 only are correct. 2 and 3 only are correct. 1, 2 and 3 only are correct. 43. The following reaction occurs in the cooling system of a nuclear power plant. C(s ) + H2O(g) H2(g) + CO(g) ∆H = + 131 kJ mol−1 Which of the following best explains why the forward reaction is more likely to occur at high temperature? 1 It has a high activation energy. 2 The equilibrium position lies to the left at low temperatures. 3 H2 and CO do not react at high temperatures. 44. The Boltzmann distribution curve at a given temperature is shown below. Which of the following statements are correct when the temperature increases? 1 The highest point of the curve is displaced to the right. 2 More molecules have higher energy. 3 The total number of molecules remains the same. 45. Tin and lead are elements of Group 14 in the Periodic Table. Which of the following statements are true about tin and lead? 1 Both their tetrachlorides show high thermal stability. 2 Both elements are good conductors of heat. 3 Both their dioxides are amphoteric. 46. The volatility of chlorine, bromine and iodine are affected by the following factors. 1 Electronegativity 2 Proton number 3 Relative molecular mass Fraction of molecules Energy Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL A B C D 1 only is correct. 1 and 2 only are correct. 2 and 3 only are correct. 1, 2 and 3 only are correct. 47. Which of the following statements is/are true of the complex [Ni(NH3)4Cl2]? 1 The name of the complex is tetraamminedichloronickel(II). 2 The geometry of the complex is octahedral. 3 The ligands present in the complex are monodentate ligands. 48. A polymer with the following repeating unit is shown below. CH3 H O | | || —O— C — C — C— | | H H Which of the following statements can be deduced from the structure above? 1 It is a polyester. 2 Its monomer is HOCH2CH2CH2COOH. 3 It produces white fumes with PCl5. 49. Which of the following reagents react with both ethanal and benzaldehyde? 1 Alkaline iodine solution. 2 2,4-dinitrophenylhydrazine 3 Tollens’ reagent. 50. Bromine is allowed to react separately with the following hydrocarbons: hexane, hexene, benzene and methylbenzene. Which of the following pairs of hydrocarbons will give the same observations? 1 Hexane and benzene. 2 Hexane and hexene. 3 Hexene and methylbenzene. Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL Identity card number………………………........................... Centre number/index number:............... (Nombor kad pengenalan) (Nombor pusat/angka giliran) 962/2 PEPERIKSAAN PERCUBAAN SIJIL TINGGI PERSEKOLAHAN MALAYSIA CHEMISTRY PAPER 2 Two and a half hours For examiner’s use 1 2 3 4 5 6 7 8 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. Answer all 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 fresh sheet of paper and arrange your answers in numerical order.Tie your answer sheets to this question paper. Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL Section A [ 40 marks ] Answer all questions in this section. 1. The lattice energies of lithium chloride and sodium chloride are – 848 kJ mol−1 and – 776 kJ mol−1 respectively. ( a ) Define the term lattice energy by using lithium chloride as an example. [2] ....................................................................................................................................................... ....................................................................................................................................................... ....................................................................................................................................................... ( b ) Explain why the lattice energy of lithium chloride is more exothermic than that of sodium chloride. [2] ....................................................................................................................................................... ....................................................................................................................................................... ( c ) State the relationship between lattice energy, enthalpy change of hydration ( ∆Hhyd) and the enthalpy change of solution ( ∆Hsoln ). [1] ....................................................................................................................................................... ( d ) The values of the enthalpy change of hydration ( ∆Hhyd) for a few ions are given in the following table . Ion Enthalpy change of hydration ( ∆Hhyd)/ kJ mol−1 Li+ – 499 Cl− – 381 ( i ) Draw a Born-Haber cycle to determine the enthalpy change of solution (∆Hsoln ) of lithium chloride. [2] ( ii ) Calculate the enthalpy change of solution ( ∆Hsoln ) of lithium chloride. [2] ( iii ) How would you expect the temperature to change when lithium chloride is dissolved in water? [1] ....................................................................................................................................................... Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 2 The Haber process is used in the industrial production of ammonia. The reaction equation is as follows. N2(g) + 3H2(g) 2NH3(g) ∆H θ = -92 kJ mol (a) At a temperature of 500o C and a pressure of 500 atm, the system is in a state of dynamic equilibrium. Explain what is meant by the term dynamic equilibrium. [2] …………………………………………………………………………………………............... …………………………………………………………………………………………............... (b) (i) Name a catalyst for the Haber process. …………………………………….………………………………………………… (ii) Explain why the catalyst in (i) does not alter the equilibrium position in this process. [2] …………….…………..…………………………………………………………… (c) Ammonia gas forms dense white fumes of ammonium chloride when reacted with hydrogen chloride gas. (i) Write an equation for the reaction .................................................................................................................................... (ii) State the hybrid orbitals of the nitrogen atom in ammonia and ammonium chloride. Ammonia : ……………………………………………………………………………………... Ammonium chloride: ……….. …………………………………………………………............................ (iii) Explain why ammonia can act as a ligand in a complex ion. ……………………………………………………………………………………... (iv) State the contents of a tank of ammonia gas which is left to stand in a hot spot for a few days. Give a reason for your answer. ………..…..………………………………………………………………............... ..…………………………………………………………………………….............. [6] Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 3. Some elements of the third period are as follows: Na, Mg, Al, Si, P, Cl, Ar. (a) Which of the elements exist as diatomic molecules at room temperature and pressure? [1] ....................................................................................................................................... (b) Which element has the largest first ionisation energy? [1] ....................................................................................................................................... (c) (i) Which of these elements form a simple covalent chloride that reacts with water to give a white precipitate? [1] …................................................................................................................................... (ii) Write an equation for the reaction in (c) (i). [1] …................................................................................................................................... (d) (i) Name an element that forms an amphoteric oxide. [1] ………............................................................................................................................ (ii) Write equations to show the amphoteric nature of the oxide in ( d ) ( i ) with HCl(aq) : ................................................................................................ ....................... NaOH(aq): …….............................................................................................................. [2] (e) Chlorine reacts with NaOH(aq) under different conditions to produce ClO− and ClO3 – ions. (i) State the conditions required to prepare ClO3 – ion. ................................................................................................................................. (ii) Write an equation for the preparation of the ClO3 – ion. ................................................................................................................................. (iii) State a use for sodium chlorate(V). .................................................................................................................................. [3] Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 4.(a) Polymers can be classified as thermoset, thermoplastic and elastomer. (i) What is meant by the term elastomer? ……………................................................................................................................. ........................................................................................................................................ (ii) Give an example of an elastomer and state a use for this elastomer. Example:....................................................................................................................................... Use : ............................................................................................................................................ [3] (b) The structures of four isomers of the hydrocarbon C4H8 are shown below. H H H H CH3 CH3 C= CH2 C=C C=C C=CH2 CH3CH2 CH3 CH3 CH3 H CH3 P Q R S (i) Which structures show geometrical isomerism? ..................................................................................................................................... (ii) When P, Q, R and S are reacted with steam, a pair of optical isomers are produced. Draw the structures of these isomers. (iii) Draw the structure of the organic product formed when S is reacted with the following reagents. Cold KMnO4(aq) : Hot acidified KMnO4(aq) : HCl(g): [7] Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL Section B [ 60 marks ] Answer any four questions in this section. 5. ( a ) The preparation of coal gas involves the following reaction: H2O( g ) + C( s ) H2( g ) + CO( g ) ∆H = + 131 kJ mol–1 ( i ) State and explain the effect of an increase in pressure and temperature on the position of equilibrium . [4] ( ii ) At 700○C, the partial pressures of steam and hydrogen are 90 kPa and 183 kPa respectively at equilibrium. Write an expression for the equilibrium constant, Kp , in terms of partial pressure and give its units. Hence, calculate the value of Kp. [4] ( b ) Ethanoic acid is a weak acid. It is used as a flavouring and a food additive in our diet. ( i ) Define the asid dissociation constant, Ka, of ethanoic acid. [1] ( ii ) Calculate the pH of a 1.0 dm3 solution containing a mixture of 0.40 mol dm–3 of ethanoic acid and 0.20 mol dm–3 of sodium ethanoate solution. [Ka, of ethanoic acid = 1.80 x 10–5 mol dm–3 ] [3] ( iii ) Calculate the change in the pH value recorded when 0.050 mol of sodium hydroxide is added to 1.0 dm3 of distilled water. [3] 6. ( a ) State Hess’ Law. [2] ( b ) ( i ) Define standard enthalpy of combustion for carbon monoxide and write the equation for the reaction involved. (ii) By using the data below, calculate the standard enthalpy of combustion for carbon monoxide. 2 Fe (s) + 3/2 O2 (g) Fe2O3(s) ∆H Θ = -822kJ Fe2O3(s) + 3 CO (g) 2 Fe(s) + 3 CO2 (g) ∆H Θ = -27kJ [6] (iii) Based on the data below, explain why sodium metal reacts vigorously and exothermically with chlorine gas. Na(s) Na+ (g) ∆H Θ = +604kJmol-1 ½ Cl2 (g) Cl- (g) ∆H Θ = -260kJmol-1 [7] Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL 7. (a) What do you understand by the term complex ion ? [3] (b) (i) Name and state the shape of [Cu(NH3)4 ] 2+ ? (ii) Name the complex ion [Cr(NH3)4Cl2] 2+ . This complex ion exhibit isomerism. Identify the type of isomerism involved and draw its isomers. [6] (c) Transition metals or its compounds are widely used in heterogenous catalytic activity.. Give a brief description of the use of a heterogeneous catalyst in the Contact Process. [6] 8. (a) Aluminium is the most abundant metal on earth.It is commonly found as a component in the structure of silicate clays containing aluminium oxide layers. Aluminium ions might be present within the silicate layers. (i) Describe how the aluminium oxide layers is involved in the structure of 2:1 clay such as montmorillonite. [2] (ii) Why is soil containing montmorillonite are not suitable for agriculture. [2] (b) (i) Explain why an aqueous solution of aluminium salts is acidic. Write an equation to show the reaction involved. [4] (ii) Explain the effect of the charge density of Al3+ ions on bonding. Describe why aluminium chloride sublimes. [7] 9. (a) The structural formula of 2-phenylmethyl-butan-2-ol is shown below. (i) Identify two possible pairs of Grignard reagent and another respondent chemical substance that can be used to prepare 2-phenylmethyl-butan-2-ol. [4] (ii) Write an equation for the reaction above. [1] Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL (b) When chlorine gas is bubbled through methylbenzene, a compound Q is produced. It can be prepared by using Grignard reagents.Compound Q has the molecular formula, C7H7CI. It forms a white precipitate on warming with ethanolic silver nitrate. (i) Write all the structural formulae of isomers with the molecular formula C7H7C1. [4] (ii) Which of the compounds in b(i) is produced in the above reaction? State the conditions for the reaction. [2] (iii) Write the chemical equation for the reaction between Q and ethanolic silver nitrate. [2] (iv) Explain why ethanolic silver nitrate and not aqueous silver nitrate is used for the reaction. [2] 10. (a) An organic compound P with relative molecular mass of 126.5 has the following composition by mass: carbon, 66.4%; chlorine, 28.1%; and hydrogen, 5.5%. (i) Determine the molecular formula of P. (ii) When P is refluxed with aqueous potassium hydroxide, Q is formed. Controlled oxidation of Q produces R that gives an orange precipitate S with 2,4-dinitrophenyhydrazine. Continued oxidation of R produces T, a white solid. Determine the structural formulae of P, Q, R, S and T. [8] (b) 2-bromo-2-methylpropane undergoes hydrolysis when boiled with aqueous potassium hydroxide. (i) Describe the mechanism of the hydrolysis. (ii) State the effect of the concentration of aqueous potassium hydroxide on the rate of hydrolysis. [7] Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
PEPERIKSAAN PERCUBAAN SIJIL TINGGI PERSEKOLAHAN MALAYSIA 2008 CHEMISTRY 1 1 D 11 A 21 A 31 B 41 A 2 A 12 C 22 A 32 C 42 C 3 A 13 D 23 A 33 C 43 B 4 C 14 D 24 B 34 B 44 D 5 B 15 D 25 D 35 B 45 C 6 B 16 C 26 A 36 D 46 C 7 C 17 B 27 B 37 A 47 D 8 C 18 C 28 C 38 D 48 A 9 C 19 C 29 B 39 B 49 C 10 A 20 D 30 A 40 B 50 A Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 1 STPM Trial Examination 2008 Chemistry Paper 2 Marking scheme Section A [40 marks] 1.( a ) Energy released when one mole of lithium chloride is formed from 1 mole of Na+ (g) and 1 mole of Cl– (g) ions under standard conditions. [2M] ( b ) Lattice energy is inversely proportional to size of cation. Size of Li+ smaller than Na+ [2M] ( c ) ∆Hsoln = ∆Hhyd – lattice energy [1M] ( d ) ( i ) Li+ ( g ) + Cl− ( g ) LiCl ( s ) Li+ (aq ) + Cl– ( aq ) [2M] ( ii ) ∆Hsoln = [ (– 499 ) + (– 381) ] – [ – 848 ] = – 32 kJ mol−1 [2M] ( iii ) Temperature increases [1M] Total : 10 M Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 2 2. (a) the rates of the forward and reverse reactions are the same 1M the amount of substances present does not change with time 1M (b) (i) iron 1M (ii) catalyst increases the rate of the forward and reverse reaction by the same amount 1M (c) (i) NH3 + HCl → NH4Cl 1M (ii) sp3 hybrid orbitals, 1M sp 3 hybrid orbitals 1M (iii) N atom has an unbonded pair of electrons to be donated to the central atom 1M (iv) hydrogen and nitrogen gases 1M ammonia has dissociated to the two gases. 1M 3.( a ) Cl [1M] ( b ) Ar [1M] ( c ) ( i ) Si [1M] ( ii ) SiCl4 + 2H2O SiO2 + 4HCl [1M] ( d ) ( i ) Aluminium [1M] ( ii ) Al2O3 + 6HCl 2AlCl3 + 3H2O Al2O3 + 2NaOH + 3H2O 2Na [Al(OH)4]4 [2M] ( e ) ( i ) hot, concentrated NaOH [1M] ( ii ) 3Cl2 + 6NaOH 5NaCl + NaClO3 + 3H2O [1M] ( iii ) weedkiller ( etc...) [1M] Total : 10M 4.( a ) ( i ) Polymers that are stretchable. [1M] ( ii ) natural rubber ( etc....) [1M] to make gloves,...... [1M] Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 3 CH2CH3 H CH3 HO C CH3 CH3CH2 OH H ( b ) ( i ) Q and R [2M] ( ii ) [2M] ( iii ) Cold KMnO4(aq): CH3 H | | H3C ― C ― C ―H | | OH OH [1M] Hot acidified KMnO4(aq): CH3 | C = O | CH3 [1M] HCl(g) : Cl H | | H3C ― C ― C ―H | | CH3 H [1M] Total : 10M C Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 4 H2 CO H2O H2 H2O [ CH3COO− ] [ CH3COOH ] Section B [60 marks] 5.( a ) ( i ) Pressure increased : Position of equilibrium shifts to the left. Backward reaction involves a reduction in volume. Temperature increased: Position of equilibrium shifts to the right. Forward reaction is endothermic. [4M] ( ii ) ( P ) ( P ) Kp = kPa ( P ) P = PCO = 183kPa , P = 90 kPa Kp = 90 x183183 = 3.72 x 103 kPa [4M] ( b ) ( i ) [CH3COO− ][ H+ ] Ka = [1M] [CH3COOH] ( ii ) pH = pKa + lg = −lg ( 1.80 x 10−5 ) + lg( 40.0 20.0 ) = 4.44 [3M] ( iii ) [ H+ ] = 050.0 1000.1 −14 x = 2.00 x 10−13 mol dm−3 pH = −lg [ H+ ] = 12.70 Therefore, change in pH = 12.70 − 7.00 = 5.70 [3M] Total : 15M Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 5 6.(a) It states that the heat evolved or absorbed in a chemical change is the same whether the change is brought about in one stage or through intermediate stages. [1] (b) (i) The enthalpy change when one mole of carbon monoxide is completely burnt in oxygen under the standard conditions of 298K and 1.0 atm. [1] CO (g) + 1/2 O2 (g) CO2 (g) [1] (ii) Equation 1: CO (g) + 1/2 O2 (g) CO2 (g) ∆H Θ c [1] Equation 2: 2 Fe (s) + 3/2 O2 (g ) Fe2O3(s) ∆H Θ = -822kJ Equation 3: Fe2O3(s) + 3 CO (g ) 2 Fe(s) + 3 CO2 (g) ∆H Θ = -27kJ Add equations (2) and (3), [1] 3CO (g) + 3/2 O2 (g) 3 CO2 (g) [1] ∆H Θ = (-822) + (-27) = -849 kJ [1] ∆H Θ c = -283kJmol-1 [1] (b) Na (s) + ½ Cl2(g) NaCl(s) ∆H Θ f [1] Na+ (g) + Cl- (g) NaCl(s) ∆H = lattice energy [1] ∆H Θ f = 604 – 260 + ∆H [1] Since NaCl is ionic , its lattice energy is very negative. [1+1] So, ∆H Θ f is very exothermic [1] The lattice energy is sufficient to overcome the enthalpy of atomisation and ionization energy of sodium [1] Total mark: 15M Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 6 7(a) An ion containing a central metal ion with empty orbitals and ligands with lone pair electrons. Ligand forms dative bond with the central metal ion. [3M] (b)(i) Tetraamminecopper(II) ion [1M] Square planar [1M] ( ii ) Tetraamminedichlorochromium(III) ion [1M] Geometrical /Cis-trans isomerism [1M] trans cis Cl Cl NH3 H3N H3N NH3 Cr Cr NH3 H3N Cl H3N Cl NH3 [2M] (c) Involves reactants and catalyst in different phases. [1M] Finely-divided platinum metal and vanadium pentoxide used as catalyst [1M] SO2(g) + O2(g) --- > SO3(g) [1M] SO2 and O2 molecules are initially adsorped on the surface of the solid catalyst. [1M] Bonds between atoms in the molecules are weaken. [1M] Ea is lowered. [1M] Total : 15 M Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 7 8. (a) (i) The aluminium oxide ( gibbsite) layer is sandwiched between two silicate layers. 1M Four oxygen atoms are shared between one AlO6 unit and two SiO4 units 1M (ii) No hydrogen bonding in the 2:1 clay arrangement 1M Little attraction between the silicon oxygen of the tetrahedral(Silicon/ oxygen ) sheets in the different layers. 1M (b) (i) The aqueous solution of aluminium salts contains hydrated aluminium ion of [Al(H2O)6 ]3+. 1M The high charge density of the Al3+ ion polarizes the O-H bonds of water 1M of water molecules and this weakens some of the bonds. One or more of the water molecules can donate a proton to produce H3O + 1M [Al(H2O)6] 3+ + H2O [ Al(H2O)5(OH)]2+ + H3O + 1M (ii) Due to high charge density ( charge/radius) ratio of Al3+ ion,the ion 1M is able to polarise the electron cloud of an anion such as O2- or Cl- 1M to give a high degree of covalent character in the ionic bond. 1M At room conditions, aluminium chloride exists in the dimeric form 1M of Al2Cl6 with weak van der waal forces between the discrete Al2Cl6 molecules. 1M Due to the weak forces between molecules ,the solid Al2Cl6 sublime to give Al2Cl6 vapour. [1M] Total: 15M Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 8 9.(a) 2-phenylmethylbutan-2-ol is a tertiary alcohol. Hence, a Grignard reagent and a ketone is required for the reaction. (i) Any two of these pairs. [4M] (ii) [1M] (b) (i) [4M] Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 9 9(a)(ii) Compound (I) , is produced. Compounds (II), (III) and (IV) do not react with AgNO3. Conditions: Pass chlorine into methylbenzene boiling under reflux and in the presence of sunlight. [2M] (iii) [2M] (iv) is insoluble in water, but soluble in ethanol. So ethanolic silver nitrate is used to enable to dissolve in the reaction mixture. [2M] Total : 15 M Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 10 10. (a) (i) Element C Cl H % by mass 66.4 28.1 5.5 Mole ratio 66.4 =5.5 12 28.1 = 0.79 35.5 5.5 = 5.5 1 Simplest ratio 7 1 7 Empirical formula of P is C7H7Cl [2M] (12x7 + 7 + 35.5)n = 126.5 n = 1 Molecular formula is C7H7Cl [1M] (ii) P is an aromatic compound [ ratio C:H is 1:1] Cl atom is on side chain since it can be hydrolysed. P is [1M] Hydrolysis of P produces phenyl methanol, Q + KOH → + KCl [1M] Controlled oxidation of Q produces benzaldehyde, R + (O) → + H2O [1M] Benzaldehyde, R reacts with 2,4-dinitrohydrazine to form a hydrazone,S CH2Cl CH2Cl CH2OH CH2OH CHO Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 11 + + H2O 1M Further oxidation of benzaldehyde, R produces benzoic acid (T) + (O) → 1M (b) (i) Nucleophilic substitution: 1M + KOH → + KBr 1M Mechanism: Dissociation of 2-bromo-2-methylpropane to produce a carbonium ion: 1M Combination of the carbonium ion with OH- from KOH: + OH - 1M CHO COOH C = O H H2N NH NO2 NO2 NH NO2 NO2 C = N H C CH3 CH3 CH3 Br C CH3 CH3 CH3 Br slow C CH3 CH3 CH3 ○+ + Br - C CH3 CH3 CH3 OH C CH3 CH3 CH3 ○+ C CH3 CH3 CH3 OH Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/
CONFIDENTIAL CONFIDENTIAL 12 (ii) The rate equation is rate = k[2-bromo-2-methylpropane] 1M is independent of conc [OH] or [KOH] 1M hence, concentration of KOH has no effect on rate. 1M Total : 15 M Pahang Trial STPM 2008 http://edu.joshuatly.com/ http://www.joshuatly.com/