DHS Prelim P2 QP

This question paper consists of 21 printed pages and 1 blank page. © DHS 2018 [Turn over Name: Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination 2018 Year 6 H2 CHEMISTRY 9729/02 Paper 2 Structured Questions 13 September 2018 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet INSTRUCTIONS TO CANDIDATES 1 Write your name, index number and class on this cover page. 2 Write in dark blue or black pen. 3 You may use an HB pencil for any diagrams or graphs. 4 Do not use staples, paper clips, glue or correction fluid. 5 Answer all questions in the spaces provided on the Question Paper. The number of marks is given in brackets [ ] at the end of each question or part question. You are advised to show all workings in calculations. You are reminded of the need for good English and clear presentation in your answers. For Examiner’s Use Question No. Marks 1 13 2 12 3 25 4 10 5 15 Total 75

2 © DHS 2018 9729/02 Answer all questions in the spaces provided. 1 Isoprene, E, is an organic compound that could be used to synthesise limonene, which is commonly used in fragrances. (a) E can be synthesised from 3–methylbut–1–ene, A, in a 4–step process as follows. C A E I II III IV HCl (g) B D excess concentrated H2SO4, heat (i) B is a major product of step I. Draw the structures of compounds B, C and D. B C D [3] (ii) Suggest the reagents and conditions for steps II and III. step II : ………………………………………………………….……….………….[1] step III : …………………………………………………………….………………[1] (iii) Predict, with reasoning, whether the mixture of products formed in step I is optically active. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………………………………….……[2]

3 © DHS 2018 9729/02 [Turn Over (b) The following reaction shows an alternative route to form intermediates for the synthesis of isoprene, E. Cl Cl F GA + + other products (i) State the reagents and conditions used to form F and G from A. …………………………………………………………………………………….…[1] (ii) Predict the ratio in which F and G will be formed. …………………………………………………………………………………….…[1] (iii) Z was one of the other products formed in the reaction in (b). It was suggested that the radical, •G, is involved in the formation of Z. The mechanism of •G converting to Z is thought to involve 2 steps. 1. Delocalisation of unpaired electron forming • Z. 2. • Z reacts with Cl2 to form Z and a radical. The structures of Z, •G and •Z are as follows. G Z Z Cl Use the information above to draw out the mechanism for the conversion of •G to Z. You are advised to use skeletal or structural formula for all species, so that it is clear which bonds are broken and which are formed. Indicate any unpaired electrons by a dot (•). Use curly half-arrows to indicate the movement of unpaired electrons. [2]

4 © DHS 2018 9729/02 (iv) Describe a chemical test that could distinguish between A and F. State reagents, conditions and observations clearly in your test. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………………………………….……[2] [Total: 13]

5 © DHS 2018 9729/02 [Turn Over 2 (a) Fig 2.1 shows a bar chart of the third ionisation energy (3 rd IE) of nine consecutive elements (J to R) in Periods 2 and 3 of the Periodic Table. 3rd IE elements Fig 2.1 J K L M N O P Q R (i) Write an equation for the third ionisation energy of element J. …………………………………………………………………………………….…[1] (ii) Identify element N. …………………………………………………………………………………….…[1] (iii) Using your answers in (a)(i), (a)(ii) and the electronic configurations of the species involved, explain the following features of Fig 2.1. 1. The significantly higher 3 rd IE of N compared to O. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………………………………….……[2] 2. The lower 3 rd IE of Q than P. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………………………………….……[2]

6 © DHS 2018 9729/02 (b) Fig 2.2 shows another bar chart of the logarithm of all the ionisation energies, log (IE), of an element S against the number of electrons removed. log(IE) number of electrons removed Fig 2.2 (i) Explain the general trend shown in Fig 2.2. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………………………………….……[2] (ii) On the axes provided, draw and label the orbital which the fifth electron is removed from. x y z [1]

7 © DHS 2018 9729/02 [Turn Over (c) The Periodic Table shows helium placed at the top of Group 18. (i) Suggest why the element helium could be placed at the top of Group 2. …………………………………………………………………………………….…[1] (ii) Suggest why the element helium is not placed at the top of Group 2, by comparing one physical property. Explain your answer. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………………………………….……[2] [Total: 12]

8 © DHS 2018 9729/02 3 The ions of transition elements form complexes by reacting with ligands. (a) (i) State what is meant by the terms: • Complex …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………………………………….……[1] • Ligand …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………………………………….……[1] (ii) Two of the complexes formed by copper are Cu(H 2NCH2CH2NH2)2(OH)2 and CuCl42–. Draw three–dimensional diagrams of their structures in the boxes below and name their shapes. Cu(H 2NCH2CH2NH2)2(OH)2 CuC l42– Shape: Shape: [3] (iii) State the oxidation number of Cu in Cu(H 2NCH2CH2NH2)2(OH)2. ………………………………………………………………………………….……[1]

9 © DHS 2018 9729/02 [Turn Over (iv) Platinum forms square–planar complexes, in which all four ligands lie on the same plane as the Pt atom. There are two isomeric complexes with the formula Pt(NH 3)2Cl2. Suggest the structures of the two isomers. isomer 1 isomer 2 [3] By comparison with a similar type of isomerism in organic chemistry, suggest the type of isomerism shown here and label the isomers above. Type of isomerism: .………………………………………………………….……[1] (b) Copper forms two series of compounds, one containing copper(II) ions and the other containing copper(I) ions. (i) Complete the electronic configuration of these species. Cu: [Ar]……………….……[1] Cu(I): [Ar]………………….…[1] (ii) Explain why the following statements are true. • Copper metal is a better electrical conductor than calcium metal. • Copper( II) salts are generally coloured. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. ………………………………………………………