ADSS Prelim P2

This question paper consists of 22 printed pages including this cover page. ADMIRALTY SECONDARY SCHOOL SUBJECT : Chemistry CODE/PAPER : 6092/2 LEVEL/STREAM : Secondary 4 Express DATE : 21 August 2024 TIME : 0800h – 0945h DURATION : 1 hour 45 minutes READ THESE INSTRUCTIONS FIRST Write your name, class and register 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. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. A copy of the Periodic Table is printed on page 22. The number of marks is given in brackets [ ] at the end of each question or part question. The use of an approved scientific calculator is expected, where appropriate. DO NOT TURN OVER THIS PAPER UNTIL YOU ARE TOLD TO DO SO. PRELIMINARY EXAMINATION 2024 For Examiner’s Use Section A / 70 Section B / 10 Total / 80 NAME: NO: CLASS:

2 Section A Answer all questions. 1 Table 1.1 shows the structures of substances A, B and C. A B C Table 1.1 Use the letters A, B and C to answer the following. Each compound may be used once, more than once or not at all. Answer the following questions using the structure and bonding of the identified substance. (a) State the substance that can be used as an electrode in electrolysis. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. [3] (b) State the substance that is a liquid at room temperature. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. [3]

3 (c) State which substance can be used as a lubricant. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. [3]

4 2 The Haber process is the main industrial procedure for the production of ammonia today. In this process, ammonia is made by reacting nitrogen and hydrogen. N2(g) + 3H2(g) 2NH3(g) A smaller scale of this reaction can be performed in the laboratory using the set-up shown in Fig. 2.1. Fig. 2.1. Nitrogen and hydrogen gas are passed forward and backward over the iron wool until no further reaction is observed. (a) Suggest a reason why air must not be present in the reaction mixture. ……………………………………………………………………………………………. ……………………………………………………………………………………………. [1] (b) Explain the role of the iron wool in this reaction. ……………………………………………………………………………………………. ……………………………………………………………………………………………. [1] (c) Using the information in the set-up shown in Fig. 2.1, suggest the volume of ammonia gas produced. Explain your answer. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. [3] 75 cm3 of hydrogen iron wool 25 cm3 of nitrogen gas syringe gas syringestrong heat

5 (d) In the industry, the standard conditions for the Haber process is a temperature of 450 oC and a pressure of 200 atm. Certain companies run the Haber process at a higher pressure of 300 atm. Suggest one advantage and one disadvantage of performing the Haber process at a higher pressure. advantage…………………………………………………………………………….…. ……………………………………………………………………………………………. disadvantage...…………………………………………………………………………. ……………………………………………………………………………………………. [2] 3 Zinc sulfite, ZnSO3, is an ionic salt which is insoluble in water. (a) Given that zinc sulfite can be prepared from sulfurous acid, H2SO3. State the chemical that can be reacted with sulfurous acid to prepare zinc sulfite. ………………………………………………………………………………………….…. [1] (b) Write a balanced equation based on (a), showing state symbols. ………………………………………………………………………………………….…. [2] (c) Suggest the experimental steps required to produce a dry sample of zinc sulfite from sulfurous acid and the chemical mentioned in (a). …………….………………………………………………………………………..….………… ……………….……………………………………………………………………..….………… ………………….………………………………………………………………..…….………… ……………………………………………………………………………………………….…… [2] (d) State whether zinc sulfate, ZnSO4 be prepared using the same method as zinc sulfite, ZnSO3. Explain your answer. ………………………………………………………………………………………….…. ………………………………………………………………………………………….…. [1]

6 4 The Andrussow process is an industrial process for the production of hydrogen cyanide in the presence of platinum as a catalyst. The structural formulae of all chemicals are shown in the chemical equation below: Table 4.1 shows some information about the bonds present in the chemicals. Table 4.1 (a) Using the information in Table 4.1, calculate the enthalpy change of the chemical equation for Andrussow process. [3] (b)Using the ideas about breaking and forming bonds, explain why the enthalpy change for the Andrussow process is negative. ………………………………………………………………………………..…..… ……………………………………………………………………………………… ……………………………………………………………..…………………..…… ……………………………………………………………………………………… [2]

7 (c) Draw the energy profile diagram for the Andrussow process. Your diagram should show and label  reactants and products  the enthalpy change, ΔH and activation energy, Ea [3] (d)To speed up the Andrussow process, a small amount of powdered platinum is added. Use ideas about energy and collisions to explain how powdered platinum speeds up the process. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… [3] Progress of reaction Energy / kJ

8 5 The body obtains iodine from certain food to make thyroid hormones. When iodine is added to starch solution, a dark blue colour is observed. Aqueous iodine reacts with sodium thiosulfate. The chemical equation of the reaction is shown below. I2 (aq) + 2Na2S2O3 (aq) → 2NaI (aq) + Na2S4O6 (aq) The concentration of iodine in an unknown sample can be determined using a known concentration of sodium thiosulfate using titration method. (a) Explain why starch is added to the analyte containing unknown concentration of iodine during the titration. …………………………………………………………………………………………….. …………………………………………………………………………………………….. [1] (b) Calculate the concentration of iodine in a 25.0 cm3 of sample given that 11.0 cm3 of 0.12 mol/dm³ of sodium thiosulfate solution is needed to reach the end point in the titration. [3] (c) Draw a ‘dot-and-cross’ diagram to show the bonding in NaI. Show only the valence electrons. [2]

9 6 Fig. 6.1 shows various reactions involving organic compounds, with ethene as the starting materials. Fig. 6.1 (a) (i) Identify W, X and Y. W: …………………………………… X: …………………………………….... Y: ……………………………………… [3] (ii) Draw the full structural formula of Z. [1] (b) Name the following processes. (i) Ethene is converted to ethanol: ……………………………………..……………… [1] (ii) Ethanol is converted to ethanoic acid: ……………………………………….….. [1] ethene ethanol X W ethanoic acid Z water Y combustion hydrogen gas