Temasek 2024 Prelim O Chem P2 SectB QP

Name: Index Number: Class: _______ TEMASEK SECONDARY SCHOOL Preliminary Examination 2024 Secondary 4 Express CHEMISTRY 6092/02 Paper 2 (Section B) Total duration for Sections A and B: 1 hour 45 minutes Candidates answer on the Question Paper. No additional Materials are required. 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 an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer one question from this section. Write your answers in the spaces provided on the question paper. At the end of the examination, submit Section A and B separately. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 7 in Section B. The use of an approved scientific calculator is expected, where appropriate. FOR EXAMINER'S USE Section B /10 This document consists of 7 printed pages and 1 blank page.

2 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School Section B Answer only one question from this section. Write your answers in the spaces provided. B11 Hydrogen peroxide is a colourless liquid. An aqueous solution of hydrogen peroxide reacts with the iodide ions in acidified potassium iodide to form water and iodine. …… H2O2(aq) + ……. H+(aq) + ..….. I ‾(aq) → …… H2O(l) + …… I2(aq) (a) Balance the above ionic equation. [1] (b) Identify the reducing agent in this reaction. Explain your answer using electrons transfer. Reducing agent : …………………………………………………..…… Explanation: …………………………….……………………………………………… …………………………….……………………………………………… [2] (c) Describe the observation seen during the reaction. …………………………….……………………………………………… [1]

3 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School (d) Table 11.1 shows how the speed of this reaction changes when different concentrations of potassium iodide and sulfuric acid are used. The hydrogen peroxide used in the reaction is always in excess and the temperature is kept constant. Table 11.1 experiment concentration of potassium iodide in mol/dm3 concentration of sulfuric acid in mol/dm3 speed of reaction in mol/dm3 per second 1 0.1 0.1 0.00017 2 0.2 0.2 0.00034 3 0.1 0.2 0.00017 4 0.3 0.1 0.00051 5 0.1 0.3 0.00017 Using the information in Table 1 1.1, describe how increasing the concentration of the following reagents affect the speed of reaction. (i) potassium iodide ……………………………………………………………………... ……………………………………………………………………... ……………………………………………………………………... ……………………………………………………………………... [2] (ii) sulfuric acid ……………………………………………………………………... ……………………………………………………………………... ……………………………………………………………………... ……………………………………………………………………... [2]

4 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School (e) Explain, in terms of Collision Theory, the effect of increasing the temperature on the speed of reaction between hydrogen peroxide and acidified potassium iodide. ……………………………………………………………………............ ……………………………………………………………………............ ……………………………………………………………………............ ……………………………………………………………………............ ……………………………………………………………………............ ……………………………………………………………………............ [2] [Total: 10]

5 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School B12 Zinc nitrate is a white crystalline solid which is soluble in water and alcohol. It is used in the synthesis of nanowires and can be used as a component in dyeing. (a) Zinc nitrate decomposes when heated to form zinc oxide, oxygen and nitrogen dioxide. Zinc nitrate can be prepared by the reaction of zinc oxide with dilute nitric acid. (i) Write a balanced chemical equation for the decomposition of zinc nitrate. ……………………………………………………………………. [1] (ii) State the colour change of the solid as zinc nitrate is heated until it has fully decomposed. ……………………………………………………………………. [1] (iii) Describe how pure and dry solid zinc nitrate is prepared and obtained from the starting reagents mentioned above. …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… [3] (b) Table 12.1 shows a series of tests that were carried out on solution X which is a solution of zinc nitrate.

6 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School Table 12.1 test number tests observations 1 An equal portion of aqueous sodium carbonate is added to solution X. 2 Aqueous ammonia is added to solution X. A white ppt is seen. 3 Aqueous sodium hydroxide and aluminium foil are added to solution X and the mixture is warmed. (i) Write the ionic equation for the formation of the white precipitate in test number 2. ……………………………………………………………………. [1] (ii) Describe the observation expected if excess aqueous ammonia was added to the precipitate in Test 2. ……………………………………………………………………. ……………………………………………………………………. [1] (iii) Complete the observations expected for Tests 1 and 3 in the empty spaces provided in Table 1 2.1. Include any test for gas and identify the gas if necessary. [3] [Total: 10] End of Section B

7 The Periodic Table of Elements Group 1 2 13 14 15 16 17 18 Key 1 H hydrogen 1 2 He helium 4 3 Li lithium 7 4 Be beryllium 9 proton (atomic) number atomic symbol name relative atomic mass 5 B boron 11 6 C carbon 12 7 N nitrogen 14 8 O oxygen 16 9 F fluorine 19 10 Ne neon 20 11 Na sodium 23 12 Mg magnesium 24 3 4 5 6 7 8 9 10 11 12 13 Al aluminium 27 14 Si silicon 28 15 P phosphorus 31 16 S sulfur 32 17 Cl chlorine 35.5 18 Ar argon 40 19 K potassium 39 20 Ca calcium 40 21 Sc scandium 45 22 Ti titanium 48 23 V vanadium 51 24 Cr chromium 52 25 Mn manganese 55 26 Fe iron 56 27 Co cobalt 59 28 Ni nickel 59 29 Cu copper 64 30 Zn zinc 65 31 Ga gallium 70 32 Ge germanium 73 33 As arsenic 75 34 Se selenium 79 35 Br bromine 80 36 Kr krypton 84 37 Rb rubidium 85 38 Sr strontium 88 39 Y yttrium 89 40 Zr zirconium 91 41 Nb niobium 93 42 Mo molybdenum 96 43 Tc technetium – 44 Ru ruthenium 101 45 Rh rhodium 103 46 Pd palladium 106 47 Ag silver 108 48 Cd cadmium 112 49 In indium 115 50 Sn tin 119 51 Sb antimony 122 52 Te tellurium 128 53 I iodine 127 54 Xe xenon 131 55 Cs caesium 133 56 Ba barium 137 57–71 lanthanoids 72 Hf hafnium 178 73 Ta tantalum 181 74 W tungsten 184 75 Re rhenium 186 76 Os osmium 190 77 Ir iridium 192 78 Pt platinum 195 79 Au gold 197 80 Hg mercury 201 81 Tl thallium 204 82 Pb lead 207 83 Bi bismuth 209 84 Po polonium – 85 At astatine –