H1 Paper 2 (Student Copy)

Name and Form Class Index Number Subject Tutor ANGLO-CHINESE JUNIOR COLLEGE DEPARTMENT OF CHEMISTRY Preliminary Examination CHEMISTRY 8872/02 Higher 1 Paper 2 22 August 2012 2 hours Candidates answer Section A on the Question Paper. Additional Materials: Writing Paper Data Booklet READ THESE INSTRUCTIONS FIRST Write your index number and name on all the work yo u hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs or ro ugh working. Do not use staples, paper clips, highlighters, glue or correction fluids. Section A Answer all questions Section B Answer two questions on separate answer paper. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A B5 B6 B7 Total This document consists of 16 printed pages. 8872/Prelims/12 ANGLO-CHINESE JUNIOR COLLEGE © ACJC 2012 Department of Chemistry [Turn over

© ACJC 2007 9746/01/Prelim/07 2 Section A Answer all questions in this section in the spaces provided 1 (a) In an attempt to determine the hydroxide concentrat ion in a titration procedure, a student filled up the burette with sod ium chloride instead of hydrochloric acid and starts the titration. He real ised something was amiss when the methyl orange indicator did not show any colour change. If he had correctly filled the burette with hydroch loric acid and carried out the titration, what is the expected colour change at the end point? ……………………………………………………………………………………. [1] For Examiner’s use (b) The student pipetted a 50.0 cm 3 sample containing sodium chloride and sodium hydroxide which he had wrongly prepared in (a) , and titrated it with hydrochloric acid. The end point was reached w hen 13.00 cm 3 of 0.35 mol dm -3 of hydrochloric acid was added. Calculate the concentration of sodium hydroxide present in the 50.0 cm 3 sample. [1] (c) 22.00 cm 3 of 0.45 mol dm -3 of acidified KMnO 4 was added in excess to oxidise the chloride ions present in (b) . The excess KMnO 4 required 14.80 cm 3 of 0.60 mol dm -3 of hydrogen peroxide solution for complete reaction. (i) KMnO 4 undergoes a redox reaction with H 2O2. Define the terms in italics. …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… (ii) Write the half equation for the oxidation of hydrog en peroxide to oxygen, and hence the overall balanced equation for the reaction For Examiner’s

© ACJC 2007 9746/01/Prelim/07 [Turn over 3 between acidified KMnO 4 and hydrogen peroxide. use (iii) Calculate the amount of KMnO 4 used to react with hydrogen peroxide. (iv) Hence calculate the amount of the sodium chloride i n the 50.0 cm 3 sample pipetted in (b). [8] [Total: 10 ]

© ACJC 2007 9746/01/Prelim/07 4 2 The use of the Data Booklet is relevant to this question. An experiment was performed to determine the enthal py change of combustion of cyclohexane, C 6H12 . The following results were obtained. Volume of water used / litre 2.5 Initial temperature of water / oC 26.0 Final temperature of water / oC 96.0 Mass of spirit lamp and cyclohexane before combustion / g 62.8 Mass of spirit lamp and cyclohexane after combustion / g 47.1 For Examiner’s use (a) Define standard enthalpy change of combustion, ∆Hc o. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… [1] (b) Given the above information, calculate the enthalpy change of combustion of cyclohexane, assuming negligible loss of heat to the surrounding. [2] (c) Using your answer in (b) and the data given below, calculate the standard enthalpy change of formation, /uni2206Hf o, of cyclohexane. For Examiner’s use

© ACJC 2007 9746/01/Prelim/07 [Turn over 5 /uni2206H c o(C) = –393.5 kJ mol –1 /uni2206Hf o (H 2O) = –285.9 kJ mol –1 C6H12(l) + 9O 2(g) → 6CO 2(g) + 6H 2O( l) 6C(s) + 6H 2(g) + 9O 2(g) [2] (d) In another experiment, cyclohexane undergoes reacti on with bromine to give a mixture of dibromocyclohexane. (i) State the condition required for the reaction to ta ke place and draw the structural formulae of all possible dibromocyclohexane. (ii) Identify the type of isomerism exhibited by the mix ture of dibromocyclohexane For Examiner’s use

© ACJC 2007 9746/01/Prelim/07 6 …………………………………………………………………………….. (iii) State the hybridisation of all the carbon atoms pre sent in dibromocyclohexane and sketch the shape of the hybr id orbitals around each carbon. [5] [Total: 10] 3 (a) Describe the reactions and write the equations when samples of sodium is For Examiner’s use

© ACJC 2007 9746/01/Prelim/07 [Turn over 7 (i ) added to water, …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… (ii) burned in the air. …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… [3] (b) 2-chloropropane, CH 3CHC lCH 3, can be hydrolysed by NaOH (aq) to form propan-2-ol. Results of an investigation into the k inetics of this reaction are given below. Experiment number [CH 3CHC lCH 3] / mol dm -3 [NaOH] / mol dm-3 Relative initial rate 1 0.10 0.20 1.00 2 0.20 0.10 2.00 3 0.30 0.20 3.00 4 0.60 0.40 6.00 (i) Use the data in the table to deduce the order of re action with respect to CH 3CHC lCH 3 and with respect to NaOH. For Examiner’s use

© ACJC 2007 9746/01/Prelim/07 8 (ii) Hence, write a rate equation for the reaction betwe en CH 3CH 2ClCH 3 and NaOH. …………………………………………………………………………….. (iii) Changing the temperature of the reaction mixture wi ll affect the rate of the reaction. With the aid of a suitable di agram, explain how increasing the temperature of the reaction mixture affects the rate of the reaction. …………………………………………………………………………… …………………………………………………………………………… ……………………………………………………………………… …… …………………………………………………………………………… (i v) Given that the half-life of 2-chloropropane is 50 s econds, how long will it take for a solution of 2-chloropropane in experiment 4 to reach a concentration of 0.15 mol dm -3? For Examiner’s use

© ACJC 2007 9746/01/Prelim/07 [Turn over 9 [7] [Total: 10] 4 Ethylbenzene is an important organic compound in th e petrochemical industry as an intermediate in the production of styrene, which is used for making polystyrene. A synthetic route involving eth ylbenzene is shown below. For Examiner’s use

© ACJC 2007 9746/01/Prelim/07 10 CH2CH3 CH2CH2CN CH2CH3 Cl HC Cl CH2 (a) Draw the structures of Compound A and Compound B in the boxes above, and fill in the table below, stating the rea gents and conditions for Step 1 – 3 in the above synthetic route. Name the type of rea ction for each step. Step Reagents and conditions Type of reaction 1 2 3 [8]