Pure Chem CHS Sec 3 Section C

1 [Turn Over Name: Index Number: Class: CATHOLIC HIGH SCHOOL End-of-Year Examination Secondary 3 (O-Level Programme) CHEMISTRY 2 October 2024 2 hours 15 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. Section C Answer one question. Write your answers in the spaces provided. For examiner’s use only: Total / 10 working / units / significant figures −1 if checked 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 8. The use of an approved scientific calculator is expected, where appropriate. A maximum of 1 mark will be deducted from your total mark for failure to show your working in calculations and misuse of units and/or significant figures, i.e. failure to quote units where necessary, the inclusion of units in quantities defined as ratios o r quoting answers to an inappropriate number of significant figures. This document consists of 7 printed pages and 1 blank page. C

2 Section C Answer one question from this section. 10 This question is about distillation. (a) Desalination is the process of converting sea water into drinking water. Older processes used a distillation method to desalinate the water, as shown in Fig. 10.1. The removal of salt is only one stage of the process of producing drinking water from sea water. Other stages are: stage 1 removing solid particles of suspended substances such as fine sand stage 2 adding chlorine to kill bacteria that may enter the water during its distribution Explain how distillation produces ‘salt-free’ water, and suggest whether each of the stages mentioned above, stage 1 and stage 2, should happen before or after the distillation. ………………………………………………………………………...…………………………… …………………………………………………………………………...………………………… ……………………………………………………………………………...……………………… ………………………………………………………………………………...…………………… …………………………………………………………………………………...………………… ………………………………………………………………………………...…………………… …………………………………………………………………………………...………………… ……………………………………………………………………………………...………..… [4] Fig. 10.1 cold water sea water ‘salt-free’ water out HEAT

3 [Turn Over (b) Table 10.1 shows the boiling points of four different alcohols, A, B, C and D. Table 10.1 alcohol A B C D boiling point / °C 56 78 122 160 A student suggested that the set-up shown in Fig. 10.2 could be used to separate the mixture of alcohols. (i) Name apparatus X. …………………………………………..………………………………………………. [1] (ii) Apparatus X needs to have cold water flowing through it. Draw an arrow on Fig. 10.2 to show where the cold water enters apparatus X. [1] (iii) A piece of apparatus is missing from the set-up in Fig. 10.2. This means that the separation will not work. Draw on Fig. 10.2 the piece of apparatus which is missing. Explain why the separation will not work without this piece of apparatus. ………………………………………………………………...…………………………….. ………………………………………………………………...…………………………….. ……………………………………………………………..……………………………. [2] Fig. 10.2 hot water bath electric heater fractionating column mixture of alcohols A, B, C and D X

4 (iv) A hot water bath cannot be used to separate alcohols C and D. Explain why. ………………………………………………………………………………………...…….. …………………………………………………………………………………………...….. …………………………………………………………………………………………... [2] [Total: 10]

5 [Turn Over 11 This question is about experiments involving the collection of gases. (a) Fig. 11.1 shows the apparatus a student used to prepare a dry sample of chlorine gas. Chlorine is denser than air. (i) Fill in the boxes in Fig. 11.1 by naming the apparatus. [1] (ii) Use Fig. 11.1 to identify two mistakes the student made. 1 ….………………………….……………………………………..………………………. ….………………………….………..………………………………..…………………….. 2 …………………….……………………………………….………..……………………. …...………………….……………………………………….…………..…………………. ……………………………………………………………………………………………[1] (iii) Explain why the gas produced in flask 1 is passed through concentrated sulfuric acid. ………………………………………………………………………..…………………. [1] (iv) Is the reaction between hydrochloric acid and manganese(IV) oxide neutralisation? Explain your answer. …………………………………...………………………………………………………….. ……………………………………..……………………………………………………. [1] Fig. 11.1 hydrochloric acid manganese(IV) oxide concentrated sulfuric acid flask 1

6 (b) In another experiment, dilute hydrochloric acid was added to magnesium metal to produce a gas. (i) Complete the diagram in Fig. 11.2 to show how the gas produced could be collected and the volume measured. A gas syringe is not provided. [2] (ii) At the end of the experiment, there were unreacted magnesium metal and aqueous magnesium chloride solution left in apparatus A. Describe an experimental procedure to find the mass of unreacted magnesium metal and the mass of dissolved magnesium chloride in the solution in apparatus A. You may assume that magnesium chloride is stable to heat. ………………………………………………………………………...…………………….. ………………………………………………………………………...…………………….. ………………………………………………………………………...…………………….. ……………………………………………………………………………...……………….. ……………………………………………………………………………...……………….. ……………………………………………………………………………...……………….. ……………………………………………………………………………...……………….. ………………………………………………………………………………..…………. [4] [Total: 10] Fig. 11.2 apparatus A dilute hydrochloric acid magnesium

7 [Turn Over BLANK PAGE

8 [Turn Over 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 – 86 Rn radon – 87 Fr francium – 88 Ra radium – 89–103 actinoids 104 Rf rutherfordium – 105 Db dubnium – 106 Sg