CJC H1 CHEM P2 QP

[Turn over CATHOLIC JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS Higher 1 CANDIDATE NAME CLASS 2T CHEMISTRY 8872/02 Paper 2 Thursday 27 August 2015 2 hours Candidates answer Section A on the Question Paper Additional Materials: Answer Paper Data Booklet Graph Paper (2 sheets) READ THESE INSTRUCTIONS FIRST Write your name and HT group on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all the questions. Section B Answer two questions on separate answer paper. You are advised to spend not more than 1 hour for Section B. You are advised to show all working in calculations. You may use a calculator. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 15 printed pages and 1 blank page. For Examiner’s Use Section A A1 /7 A2 /14 A3 /7 A4 /3 A5 /9 Section A 40 Section B B6 /20 B7 /20 B8 /20 Section B 40 P2 Total 80 P1 Total 30 Overall % Grade

2 8872/02/CJC JC2 Preliminary Exam 2015 Section A Answer all questions in this section in the spaces provided. 1 (a) Potassium manganate (VII), KMnO 4, can be reduced by iron(II) sulfate, FeSO 4. The relevant half-equations for the reaction are given below: MnO4 – + 8H+ + 5e– ⇌ Mn2+ + 4H2O Fe3+ + e– ⇌ Fe2+ Write the balanced equation for the redox reaction which can occur. [1] ……………………………………………………………………………………..…………….... ………………………………………………………………………………………………….... (b) Ketones can be reduced by lithium aluminium hydride, LiA lH4, in dry ether to form secondary alcohols. State another set of reagents and conditions that can also be used for the reduction of ketones. [1] ………………………………………………………………………………………………..….... (c) Ketones are not easily oxidised . However, methyl ketones are a specific class of ketones with the acetyl functional group, RCOCH 3, and these can be easily oxidised in the triiodomethane test. State the conditions and reagents necessary for this test and write an equation for the reaction, using RCOCH3. [2] …………………………………………………………………………………………………….. ………………………………………………………………………………………………..….... ………………………………………………………………………………………………..….... (d) Many organic compounds undergo oxidation, albeit to varying degrees. Compare the relative ease of oxidation of benzene and methylbenzene. Write appropriate equations and state reagents and conditions to illustrate your answer. [3] ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ [Total: 7]

3 8872/02/CJC JC2 Preliminary Exam 2015 [Turn over 2 (a) Define the term relative atomic mass of chlorine. [1] ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ (b) Write the spdf electronic configuration of a chloride ion, Cl–. [1] ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ (c) (i) Draw a dot-and-cross diagram to show the bonding in calcium chloride. (ii) Explain how and why the lattice energ ies of calcium chloride , CaC l2, and potassium chloride, KCl, have different numerical values. [4] ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ ……………………………………………………………………………………………............ ……………………………………………………………………………………………............

4 8872/02/CJC JC2 Preliminary Exam 2015 The first ionisation energies of the elements lithium to fluorine is shown below. (d) (i) Describe and explain the general trend in first ionisation energies for the elements lithium to fluorine. …………………………………………………………………………………….... …………………………………………………………………………………….... …………………………………………………………………………………….... …………………………………………………………………………………….... …………………………………………………………………………………….... (ii) Describe and explain how the first ionisation energy for chlorine compares to that of fluorine. [4] …………………………………………………………………………………….... …………………………………………………………………………………….... …………………………………………………………………………………….... ……………………………………………………………………………………....

5 8872/02/CJC JC2 Preliminary Exam 2015 [Turn over (e) (i) Solid iodine burns in fluorine gas to produce iodine pe ntafluoride which has the chemical formula of IF5. Draw and state the shape of the IF5 molecule. Shape: ................................................. When liquid IF5 reacts with fluorine gas, a compound known as iodine ( VII) fluoride is formed. This has the formula of IF7 where all the fluorine atoms are evenly distributed around the central iodine atom as shown in the diagram below: IF7 IF5 and IF7 differ in their boiling points as shown in this table: Compound Boiling point /oC IF5 97.9 IF7 4.8 (ii) With reference to bonding, suggest an explanation for the difference in boiling points. [4] …………………………………………………………………………………………….... …………………………………………………………………………………………….... …………………………………………………………………………………………….... …………………………………………………………………………………………….... [Total: 14]

6 8872/02/CJC JC2 Preliminary Exam 2015 3 The hydrolysis of the ester , propyl ethanoate , gives ethanoic acid and propan -1-ol as the products. This hydrolysis is a reversible reaction which , given time, is able to achieve dynamic equilibrium. CH3CO2CH2CH2CH3(l) + H2O(l) ⇌ CH3CO2H(l) + CH3CH2CH2OH(l) propyl ethanoate (a) (i) Write an expression for the equilibrium constant, Kc of the above reaction. (ii) State one factor which affects the value of equilibrium constant of the hydrolysis reaction. …………………………………………………………………………………….... (iii) Calculate the concentration of H 2O(l) at equilibrium when the concentrations of CH3CO2CH2CH2CH3(l), CH 3CO2H(l) and CH 3CH2CH2OH(l) are 1.357 mol dm-3, 1.505 mol dm-3 and 2.353 mol dm-3respectively. Kc for this reaction is 2.535. [3] (b) (i) State the catalyst and the conditions that are used for the acidic hydrolysis of the ester. …………………………………………………………………………………......... ……………………………………………………………………………………….. (ii) Suggest why the bas e hydrolysis of esters might give a higher yield of the products compared to the acid hydrolysis of esters. [3] ……………………………………………………………………………………….. ……………………………………………………………………………………….. ………………………………………………………………………………………..

7 8872/02/CJC JC2 Preliminary Exam 2015 [Turn over (c) Draw another ester that is a structural isomer of the ester, propyl ethanoate. [1] [Total: 7] 4 Ethene, H2C=CH2, is able to undergo electrophilic addition with chlorine to form 1,2-dichloroethane. Ethyne, HC≡CH, is also able to undergo electrophilic addition with chlorine in the same way as eth ene does, but the products are a mixture of 1,2-dichloroethene and 1, 1,2,2- tetrachloroethane. (a) State the reagent and conditions necessary to have a good yield of 1,2-dichloroethene, CHCl=CHCl from ethyne. …………………………………………………………………………………………….…….... ……………………………………………………………………………………………….….... (b) 1,2-dichloroethene can exhibit geometric isomerism. Draw and label the two geometric isomers of 1,2-dichloroethene. [3] [Total: 3]

8 8872/02/CJC JC2 Preliminary Exam 2015 5 Honey does not spoil over time, unlike most types of food. In fact, the oldest known sample of honey was found in an Ancient Egyptian tomb and it was still perfectly edible. A key factor