2022 QSS Chem Prelims P2

NAME: CLASS: INDEX NO: QUEENSWAY SECONDARY SCHOOL PRELIMINARY EXAMINATION 2022 SECONDARY 4 EXPRESS CHEMISTRY 6092/02 Paper 2 13 September 2022 1 hour 45 minutes No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name and index number 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 A: Answer all questions in the spaces provided. Section B: Answer all three questions, the last question is in the form either/or. Answer all questions in the spaces 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. A copy of the Periodic Table is printed on page 25. The use of an approved scientific calculator is expected, where appropriate. This document consists of 25 printed pages. Setters: Ms Tong and Ms How [Turn over For Examiner's Use Section A /50 Q9 /12 Q10 / 8 E / O Q11 /10 TOTAL /80 Parent’s Signature:

2 SECTION A Answer all the questions in this section in the spaces provided. The total mark for this section is 50. A1 Atoms or ions that contain the: • same number of electrons are isoelectronic particles; • same number of neutrons are isotonic particles; and • same number of protons are isoprotic particles. The nuclide notations of five ions are given below. (a) Which of the five ions are (i) isoelectronic; ………………………………………………………………………………….… [1] (ii) isotonic; and ………………………………………………………………………………….… [1] (iii) isoprotic? ………………………………………………………………………………….… [1] (b) A beam of charged particles is deflected when they passed through an electric field. Particles with higher charge and lower mass are deflected more. When passed through an electric field, which of the five ions would be deflected the (i) most? ………………………………………………………………………………….… [1] (ii) least? ………………………………………………………………………………….… [1] [Total: 5]

3 A2 The table below shows the melting points of some aluminium compounds. aluminium compound melting point / oC Al2O3 2072 AlF3 1291 AlCl3 180 (a) With reference to the melting points given, suggest the structure and bonding of aluminium chloride. structure ……………………………...……………………………………………………. bonding ………………………………………………………………..……………….. [1] (b) (i) Draw the ‘dot-and-cross’ diagram for aluminium oxide. Show outer electrons only. [2] (ii) Explain why the melting point of aluminium oxide is higher than that of aluminium fluoride. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ………………………………………………………………………………….… [1] (iii) Describe and explain one other physical property of aluminium oxide. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ………………………………………………………………………………….… [2] [Total: 6]

4 A3 Carbon monoxide is used to make phosgene, COCl2, which is an important reactant in industries to make polymers, dyes, and pharmaceuticals. Phosgene was first made in 1812 by using a photochemical reaction in which a mixture of carbon monoxide and chlorine was exposed to bright sunlight. CO + Cl2 ⇌ COCl2 It has been determined that phosgene melts at –118oC and boils at 8oC. (a) Explain, using bonding and structure, why phosgene has low melting and boiling points. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ..…………………………………………………………………….…………………… [2] (b) Describe the change in arrangement and movement of the particles of phosgene when the temperature decreases from –110 oC to –130 oC. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ..…………………………………………………………………….…………………… [2] (c) Draw a ‘dot-and-cross’ diagram for phosgene, COCl2. Show outer shell electrons only. [2] [Total: 6]

5 A4 Hydrogen peroxide, H2O2, is both an oxidising agent and a reducing agent. Reactions 1 and 2 below illustrate this property of hydrogen peroxide. Reaction 1 2KI(aq) + H2O2(aq) + H2SO4(aq) → I2(aq) + K2SO4(aq) + 2H2O(l) Reaction 2 2KMnO4(aq) + 5H2O2(aq) + 3H2SO4(aq) → K2SO4(aq) + 5O2(g) + 2MnSO4(aq) + 8H2O(l) (a) In which reaction is hydrogen peroxide acting as an oxidising agent? Explain your answer. ………………………………………………………………………………………………. ………………………………………………………………………………………………. …………………………………………………………………………………………... [1] (b) State the oxidation states of manganese in: KMnO4: ………………. MnSO4: ………………. [1] (c) Describe two observations from Reaction 2. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ..…………………………………………………………………….…………………… [2] [Total: 4]

6 A5 The following set-up can be used for the electrolysis of solution Q and dilute magnesium sulfate solution using graphite electrodes. (a) (i) Write the half-equations with state symbols to show the reactions taking place at electrodes A and B. electrode A: ……………….………………….………..…………………………… electrode B: …………………………………………………………………...… [2] (ii) State and explain the change in observation for electrode A when the electrolyte is changed to aqueous silver sulfate. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ………………………………………………………………………………….… [2] (b) In the electrolysis of solution Q, a reddish-brown deposit is observed at electrode C while a yellowish-green gas is observed at electrode D. The yellowish-green gas turns moist blue litmus paper red then bleaches it. (i) Identify solution Q. ………………………………………………………………………………….… [1]

7 (ii) Calculate the volume of gas formed at electrode D if the volume of gas produced at electrode B is 30 cm3. [2] [Total: 7]

8 A6 A student places a few drops of aqueous potassium iodide on a white tile and adds a few drops of chlorine water. The student observes that the solution darkens in colour. (a) Explain the student’s observation. ………………………………………………………………………………………………. ………………………………………………………………………………………………. …………………………………………………………………………………………... [2] (b) Describe how the student could extend this experiment and use his observations to show that the reactivity of bromine is placed between that of chlorine and iodine. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. …………………………………………………………………………………………... [2] [Total: 4]

9 A7 The Haber process, which converts hydrogen and nitrogen to ammonia, is one of the most important industrial chemical reactions to be developed. The process made ammonium-based fertilisers widely available, causing a world population boom as food production increased rapidly in a short period. The diagram shows a simplified flowchart of the Haber Process in a reactor. (a) State the source of each raw material in the Haber Process. hydrogen: ……………………………………………………..…………………………… nitrogen: ………………………………………………………………..………………. [1] (b) When the mixture of gases is cooled, only ammonia changes into a liquid. Explain this observation with reference to its boiling point. ………………………………………………………………………………………………. …………………………………………………………………………………………... [1] (c) Explain why the volume ratio of nitrogen to hydrogen in the reactor is maintained at 1 : 3. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ……………………………………………………………………………………………[2]

10 (d) The ammonia produced from the Haber process is used to make fertilisers.