2019 ASRJC Prelim H2 Chem P2 QP

ASRJC JC2 PRELIMS 2019 9729/02/H2 [Turn over ANDERSON SERANGOON JUNIOR COLLEGE 2019 JC 2 PRELIMINARY EXAMINATIONS NAME:_____________________________________ ( ) CLASS: 19 /____ CHEMISTRY 9729/02 Higher 2 4 September 2019 Paper 2 Structured Questions 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, index number and class on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. 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 Paper 2 1 / 12 2 / 11 3 / 18 4 / 13 5 / 12 6 / 9 Total / 75 This document consists of 26 printed pages and 2 blank pages.

2 ASRJC JC2 PRELIMS 2019 9729/02/H2 1 (a) Use the data from Table 1.1 to state and explain the relative reactivity of Group 2 elements as reducing agents. Table 1.1 Element Eo [M2+(aq)/M(s)] / V Mg –2.38 Ca –2.87 Sr –2.89 Ba –2.90 …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… ……………………………………………………………………………………………………..… [2] (b) Table 1.2 gives data about some physical properties of calcium and copper. Table 1.2 calcium copper relative atomic mass 40.1 63.5 atomic radius (metallic) / nm 0.197 0.128 ionic radius (2+) / nm 0.099 0.069 electrical conductivity / 106 S cm1 0.298 0.596 density / g cm3 1.54 8.92 (i) Explain why the electrical conductivity of copper is higher than that of calcium. …………………………………………………………………………………………………...... …………………………………………………………………………………………………..... …………...……………………………………………………………………………………...... …………..…………………………………………………………………………………..… [2]

3 ASRJC JC2 PRELIMS 2019 9729/02/H2 [Turn over (ii) Using relevant data from T able 1.2, explain why the density of copper is significantly greater than that of calcium (no calculations are required). …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. …………………………………………………………………………………………………….. …………………………………………………………………………………………………. [2] (c) (i) Copper is a typical transition element and is used in alloys for aircraft engine parts. Which of the following “electrons –in–boxes” diagrams best describes the valence ground–state electronic configuration of a Cu+ ion? Explain your answer. 3s2 3p6 3d10 A ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿⇂ 3s2 3p6 3d10 B ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿⇂ ↿↿ …………………………………………………………………………………………………….. ….……………………………………………………………………………………………… [1] (ii) Using the Cartesian axes shown in Fig. 1.1, draw fully–labelled diagrams of any two d–orbitals of different shapes found in a Cu+ ion. Fig. 1.1 [2] x y z x y z

4 ASRJC JC2 PRELIMS 2019 9729/02/H2 (d) Silicon is the eighth most common element in the universe by mass. It very rarely occurs as the pure element in the Earth's crust. Table 1.3 shows the melting points of silica (SiO2) and silicon. Table 1.3 melting point / °C silica 1710 silicon 1414 Silica and silicon each form a solid with the same type of structure. (i) State the type of structure present in solid silica and silicon. ………………………………………………………………………………….……………... [1] (ii) Using relevant data from the Data Booklet, suggest why the melting point of silica is higher than that of silicon. ………………………………………………………………………………….…………………. ………………………………………………………………………………………….…………. ………………………………………………………………………………………………….…. …………………………………………………………………………………………………….. ………………………………………………………………………………………………… [2] [Total: 12]

5 ASRJC JC2 PRELIMS 2019 9729/02/H2 [Turn over Question 2 starts on the next page.

6 ASRJC JC2 PRELIMS 2019 9729/02/H2 2 (a) Alkene C, C7H10, on treatment with hot, concentrated potassium manganate(VII) forms an optically inactive compound D, C5H8O3, and carbon dioxide gas. D reacts with both Na2CO3 and alkaline aqueous iodine. (i) Suggest two structural features that are present in D. ………………………………………………………………………………………………….. ………………………………………………………………………………………………….. …………………………………………………………………………………………….… [2] (ii) Hence, deduce the structures of C and D. C D [2]

7 ASRJC JC2 PRELIMS 2019 9729/02/H2 [Turn over Ozone, O3, is an oxidising agent that causes carbon–to–carbon double bond cleavage. When an alkene is treated with ozone, followed by zinc metal in acetic acid, two carbonyl–containing products are obtained. The following reactions illustrate two oxidations using ozone as the oxidising agent. C CH3 CH3 1. O3 2. Zn, H3O+ + E C3H6O 1. O3 2. Zn, H3O+CHCH2CH3 + F C3H6O O O Both E and F react with 2,4–dinitrophenylhydrazine but only F reacts with Fehling’s solution. E reacts with alkaline aqueous iodine but not F. (iii) Suggest the identities of E and F. E F [2] (iv) Use the above information and your answers to (a)(iii) to suggest the structure for compound G in the following reaction. 1. O3 2. Zn, H3O+ CH3CHO + (CH3)2CHCHO G G [1]

8 ASRJC JC2 PRELIMS 2019 9729/02/H2 (b) (i) Limonene occurs in oil of lemons and is used to flavour some citrus drinks. limonene Draw the structural formula of the product, and describe what you might observe, when limonene reacts with bromine in an inert solvent, until in excess. observation ……………………………………………………………………………………. ……………………………………………………………………………………………..... [2]

9 ASRJC JC2 PRELIMS 2019 9729/02/H2 [Turn over Fig. 2.1 shows a reaction scheme involving an isomer of limonene, H. H step 1 ClCl step 2 excess HBr a mixture of isomeric products Fig. 2.1 (ii) Suggest reagents and conditions for step 1. ………………………………………………………………………………………………. [1] (iii) Draw the structure of the major product for step 2. [1] [Total: 11]

10 ASRJC JC2 PRELIMS 2019 9729/02/H2 3 Transition metals are building blocks for life and they make up the middle block of the Periodic Table. (a) Catalase is an important enzyme that reduces the damaging effects of hydrogen peroxide in the biological system. It contains four iron–containing heme groups that allow the enzyme to react with the hydrogen peroxide. It catalyses the decomposition of hydrogen peroxide into water and molecular oxygen. H2O2 → H2O + ½O2 (i) With the aid of a sketch of the Boltzmann distribution, explain why the addition of catalase speeds up the decomposition of hydrogen peroxide. …………………………………………………………………………………………………..