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GCE JUN 2007 : (AS 2) Organic, Physical and Inorganic Chemistry

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2007 Chemistry assessing Module 2: Organic, Physical and Inorganic Chemistry ASC21 Assessment Unit AS 2 [ASC21] MONDAY 18 JUNE, AFTERNOON TIME 1 hour 30 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Answer all sixteen questions. Answer all ten questions in Section A. Record your answers by marking the appropriate letter on the answer sheet provided. Use only the spaces numbered 1 to 10. Keep in sequence when answering. Answer all six questions in Section B. Write your answers in the spaces provided in this question paper. For Examiner s use only Question Number Section A 1 10 Section B 11 INFORMATION FOR CANDIDATES The total mark for this paper is 100. Quality of written communication will be assessed in question 14(c). In Section A all questions carry equal marks, i.e. two marks for each question. In Section B the figures in brackets printed down the right-hand side of the pages indicate the marks awarded to each question or part question. A Periodic Table of Elements (including some data) is provided. ASC2S7 3150 Marks 12 13 14 15 16 Total Marks Section A For each of the questions only one of the lettered responses (A D) is correct. Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet. 1 Which one of the following hydrocarbons exhibits cis-trans isomerism? A B C D 2 Which one of the following statements about ethene is correct? A B C D 3 The (pi) bond contains two shared electron pairs. The (pi) bond is readily attacked by nucleophiles. Rotation of the double bond requires breaking a (sigma) bond. The carbon to hydrogen (sigma) bond can rotate freely. Which one of the following increases on descending Group II from calcium to barium? A B C D 4 CH3CH2CH=CH2 (CH3)2C=CHCH3 CH3CH=CHCH2CH3 CH2=C(CH3)2 first ionisation energy melting point solubility of the sulphates thermal stability of the hydroxides 14.8 g of butan-1-ol (RMM 74) were refluxed with sodium bromide and sulphuric acid, after which 17.8 g of 1-bromobutane (RMM 137) were collected. What is the percentage yield of this conversion? A B C D ASC2S7 54% 65% 78% 83% 3150 2 [Turn over 5 Which one of the following reactions is not found in the mechanism for the photochlorination of methane? A B C D 6 Cl2 2Cl 2Cl Cl2 CH4 + Cl CH3Cl + H CH3 + Cl CH3Cl Which one of the following reaction profiles represents a reaction in which the reactants are kinetically and thermodynamically unstable compared to the products? A enthalpy B enthalpy C enthalpy 7 D enthalpy Which one of the following alcohols will give a positive result in the iodoform test? A B C D ASC2S7 CH3C(CH3)(OH)CH3 CH3CH2CH2CH2OH CH3CH(OH)CH2CH3 CH3CH(CH3)CH2OH 3150 3 [Turn over 8 0.8 mole of a liquid X was found to contain 19.2 g carbon, 3.2 g hydrogen and 56.8 g chlorine. What is the molecular formula of X? A B C D 9 CH2Cl C2H2Cl C2H4Cl C2H4Cl2 Which one of the following alcohols is not oxidised by acidified potassium dichromate solution? A B C D Propan-1-ol Propan-2-ol 2-methylpropan-1-ol 2-methylpropan-2-ol 10 The molecular structure and flexibility of HD polythene is best described as A B C D ASC2S7 branched and rigid. branched and flexible. unbranched and rigid. unbranched and flexible. 3150 4 [Turn over Section B Examiner Only Marks Remark Answer all six questions in the spaces provided. 11 Rennin, from calves stomachs, is an enzyme used in the hydrolysis of protein during cheese manufacture. (a) Explain the term hydrolysis. _________________________________________________________ ______________________________________________________ [2] (b) Protein hydrolysis in cheese manufacture is an exothermic process. Draw a labelled reaction profile to show both the catalysed and uncatalysed reaction pathways for this hydrolysis. enthalpy extent of reaction ASC2S7 3150 5 [2] [Turn over 12 Long chain hydrocarbons may be converted into shorter more useful ones, by catalytic cracking. Examiner Only Marks Remark (a) (i) Write an equation for the cracking of C20H42 in which pentane is one of the products. __________________________________________________ [2] (ii) Draw the structure of a branched isomer of pentane. [2] (b) A mixture of pentane and excess oxygen was ignited. The resultant gases were bubbled through concentrated sodium hydroxide solution which absorbed 115 cm3. Calculate the volume of pentane in the original mixture. _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] ASC2S7 3150 6 [Turn over 13 The synthesis stage in the manufacture of methanol involves the reaction of carbon dioxide with hydrogen as shown below. CO2(g) + 3H2(g) CH3OH(g) + H2O(g) Examiner Only Marks Remark H = 49 kJ The original process used a chromium oxide/zinc oxide catalyst. (a) Complete the table below indicating if the condition chosen increases, decreases or has no effect on the rate and yield of methanol. Condition catalyst Rate Yield increase no effect high pressure high temperature [4] (b) The distribution of molecular energies in the reaction mixture at 350 C is shown below. number of particles energy (i) Sketch, on the axes above, the distribution of molecular energies at 340 C. [1] (ii) On the axis above, draw the relative positions of the activation energy without a catalyst (EA) and the activation energy with a catalyst (EA ). [1] ASC2S7 3150 7 [Turn over (iii) Explain whether the manufacture of methanol is an example of homogeneous or heterogeneous catalysis. Examiner Only Marks Remark _____________________________________________________ __________________________________________________ [1] (iv) Use the graph on page 7 to explain the effect of decreasing the temperature on the rate of formation of methanol. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (c) Name the reagents (A C) used in the following reactions of methanol. CH3Cl B HCOOH A CH3OH C CH3ONa A _______________________________________________________ B _______________________________________________________ C ____________________________________________________ [3] (d) Methylated spirits contains ethanol (b.p. 78 C), methanol (b.p. 64 C) and water as well as other additives. (i) Explain why ethanol, methanol and water are miscible. _____________________________________________________ __________________________________________________ [2] (ii) Suggest how these three components of methylated spirits could be separated. __________________________________________________ [2] ASC2S7 3150 8 [Turn over (iii) Methylated spirits is used as a fuel for some camping stoves. Explain why the pots heated by a methylated spirits burner are often covered in a layer of black powder on the outside during use. Write an equation to support your answer. Examiner Only Marks Remark _____________________________________________________ _____________________________________________________ __________________________________________________ [3] (e) Methanol undergoes an esterification reaction when refluxed with ethanoic acid in the presence of concentrated sulphuric acid. (i) State two roles of the concentrated sulphuric acid in this reaction. _____________________________________________________ __________________________________________________ [2] (ii) Draw the structural formula of the ester formed. [2] (iii) Name the ester formed in this reaction. __________________________________________________ [1] (iv) Ethanoyl chloride can be used in place of ethanoic acid for this conversion. State two advantages of using ethanoyl chloride. _____________________________________________________ __________________________________________________ [2] ASC2S7 3150 9 [Turn over 14 Magnesium is found in minerals such as dolomite, magnesite and kieserite. Examiner Only Marks Remark (a) Dolomite has the formula CaCO3.MgCO3. (i) State one observation when dolomite is treated with dilute hydrochloric acid. __________________________________________________ [1] (ii) Write an equation for the reaction of dolomite with dilute hydrochloric acid. __________________________________________________ [2] (iii) State the colour expected when a sample of dolomite is used in a flame test. __________________________________________________ [1] (iv) Explain why calcium carbonate is more stable to heat than magnesium carbonate. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] ASC2S7 3150 10 [Turn over (b) Kieserite is hydrated magnesium sulphate. Explain how an aqueous solution of magnesium sulphate may be used to distinguish between powdered samples of sodium carbonate and sodium hydrogencarbonate. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] (c) Pure magnesite has the formula MgCO3 but is often contaminated with other minerals. Describe, without details of rinsings or calculations, the practical steps required to determine the percentage purity of a sample of magnesite using a back titration method. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [4] Quality of written communication [2] (d) It is estimated that each cubic kilometre in the ocean contains 1.2 million tonnes of magnesium. Calculate the concentration of magnesium in the ocean in mol dm 3. (1 km3 = 1012 dm3 and 1 tonne = 106 g) _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [3] ASC2S7 3150 11 [Turn over 15 The Smoky Mountains in the United States are enveloped by a blue haze which contains simple gaseous hydrocarbons emitted by trees and plants. One such hydrocarbon is isoprene, which has the structure: CH3 Remark H C H Examiner Only Marks C C C H H H Isoprene shows typical reactions of an unsaturated hydrocarbon. (a) Explain the term hydrocarbon. ______________________________________________________ [1] (b) Isoprene reacts with hydrogen bromide. (i) Draw a flow scheme for the mechanism of this reaction showing one hydrogen bromide molecule reacting with one double bond in isoprene. [3] (ii) Name the mechanism for this reaction. __________________________________________________ [2] ASC2S7 3150 12 [Turn over (c) Hydrogenation of isoprene, C5H8, involves the use of heat and a catalyst. Examiner Only Marks Remark (i) Name the catalyst used. __________________________________________________ [1] (ii) Write an equation for the complete hydrogenation of isoprene and name the product. _____________________________________________________ __________________________________________________ [3] (iii) State how you would use a chemical test to show that all of the isoprene has been saturated. _____________________________________________________ _____________________________________________________ __________________________________________________ [2] ASC2S7 3150 13 [Turn over 16 The halogenoalkanes are sweet smelling organic compounds which are used as refrigerants, propellants and in fire extinguishers. Examiner Only Marks Remark (a) Refluxing a tertiary bromoalkane with aqueous sodium hydroxide forms a tertiary alcohol. (i) Write an equation for the reaction of 2-bromo-2-methylpropane, (CH3)3CBr with aqueous sodium hydroxide. __________________________________________________ [1] (ii) 1.25 g of a tertiary bromoalkane were refluxed with 50 cm3 of 0.25 M aqueous sodium hydroxide. On completion, the excess sodium hydroxide required 16.8 cm3 of 0.25 M hydrochloric acid for neutralisation. Using the steps below, determine the mass of one mole of the bromoalkane, assuming it contains only one bromine atom. moles of sodium hydroxide reacting with hydrochloric acid. _____________________________________________________ moles of sodium hydroxide used to hydrolyse the bromoalkane _____________________________________________________ moles of the bromoalkane _____________________________________________________ mass of one mole of the bromoalkane __________________________________________________ [4] (b) Bromoalkanes react with sodium hydroxide in alcohol to give different products than with the aqueous solution. (i) Write the equation for the reaction of 1-bromobutane with sodium hydroxide in alcohol, naming the organic product. _____________________________________________________ __________________________________________________ [3] (ii) Name the type of reaction occurring in part (i). __________________________________________________ [1] ASC2S7 3150 14 [Turn over (c) Ammonia, like halogenoalkanes, is used as a refrigerant. Examiner Only Marks Remark (i) State a chemical test for ammonia. _____________________________________________________ __________________________________________________ [2] (ii) Ammonia reacts with halogenoalkanes to form amines. Write an equation for the reaction of ammonia with chloroethane. __________________________________________________ [1] (d) Bromochlorodifluoromethane, BrClF2C, is used to extinguish fires. (i) Draw a dot and cross diagram, using outer electrons only, to show the bonding in BrClF2C. [2] (ii) Suggest which carbon halogen bond is most readily hydrolysed when BrClF2C is heated with aqueous sodium hydroxide solution. __________________________________________________ [1] THIS IS THE END OF THE QUESTION PAPER ASC2S7 3150 15 [Turn over Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright holders may have been unsuccessful and CCEA will be happy to rectify any omissions of acknowledgement in future if notified. S 10/07 7-135-1

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Additional Info : Gce Chemistry June 2007 Assessment Unit AS 2Module 2: Organic, Physical and Inorganic Chemistry
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