2022 LVSS Chem Prelims P2

LOYANG VIEW SECONDARY SCHOOL Preliminary Examination 2022 Secondary Four Express CANDIDATE NAME : ……………………………………………………………….......... CLASS : …………………. INDEX NUMBER : ……………. CHEMISTRY 6092/02 Paper 2 Theory 29 August 2022 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer all three questions. The last question is in the form either/or. Answer all questions in the spaces provided. 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 21. The use of an approved scientific calculator is expected, where appropriate. Setter: Mrs Lam-Tan Siok Hiang For Examiner’s Use Section A / 50 Section B / 30 Total / 80 This paper consists of 21 printed pages.

2 Section A Answer all questions in this section in the spaces provided. The total mark for this section is 50. 1 Iron is extracted from iron ore in the blast furnace. The equations A, B, C, D and E show some reactions that happen in the blast furnace. A C + O2 → CO2 B CO2 + C → 2CO C Fe2O3 + 3CO → 2Fe + 3CO2 D CaCO3 → CaO + CO2 E SiO2 + CaO → CaSiO3 (a) Use the letters A, B, C, D and E to answer the following questions. Each letter can be used once, more than once or not at all. (i) Which equation shows neutralisation? ………………………………………………………………………….……….. [1] (ii) Which equation shows an element that undergoes both oxidation and reduction at the same time? ………………………………………………………………………….……….. [1] (iii) Which equation shows no change in the oxidation state of any element in the reactants? ………………………………………………………………………….……….. [1] (b) Blast furnace slag may contain impurities of Group IV and Group V oxides. These impurities cause the slag to be less effective in removing acidity from the soil. Explain why Group IV and Group V oxides are less effective in removing acidity. …………………………………………………………………………………………... …………………………………………………………………………………………... [1] [Total: 4]

3 2 Two students want to distinguish between two unlabelled test tubes each containing either aqueous sodium hydroxide or aqueous ammonia. Student A suggests adding aqueous zinc nitrate while student B suggests adding aqueous lead(II) nitrate into both test tubes. (a) Which student would be able to distinguish between the two unlabelled test tubes? Use the observations obtained by both students to support your answer. ………………………………………………………………………………...………… …………………………………………………………………...……………………… …………………………………………………………………...……………………… ………………………………………………………...………………………………… …………………………………………………………...……………………………… ………………………………………………………...………………………………… …………………………………………………...……………………………………… [2] (b) Aqueous ammonia can be used to make fertilisers such as ammonium nitrate. Ammonium nitrate is slightly acidic. Calcium carbonate can be added to the fertiliser so that soil does not become acidic, but calcium hydroxide should not be used. Explain why calcium hydroxide should not be added to ammonium nitrate fertiliser. ………………………………………………………………………………………….. ………………………………………………………………………………………….. ………………………………………………………………………………………….. ………………………………………………………………………………………. [2] [Total: 4]

4 3 Some elements have many isotopes. Table 3.1 shows information about three atoms of element X. Table 3.1 atom 1 2 3 number of protons 7 7 7 number of electrons 7 7 7 number of neutrons 7 8 9 number of electrons in outer shell 5 5 5 (a) Use data from Table 3.1 to show that atoms 1, 2 and 3 are isotopes of the same element. ………………………………………………………………………………...………… ……………………………………………………………………………...…………… …………………………………………………………………………...……………… [1] (b) Explain how the data suggests that the three isotopes undergo the same types of chemical reactions. …………………………………………………………………………………….…….. ……………………………………………………………………………...…………… [1] (c) Elements Y and Z also have isotopes. Table 3.2 shows information about the isotopes of elements Y and Z. Table 3.2 isotope of element Y isotope of element Z number of protons 53 38 number of electrons 53 38 number of neutrons 66 50 number of electrons in outer shell 7 2 (i) Use the information in Table 3.1, Table 3.2 and the Periodic Table to identify the elements X, Y and Z. X ……………………………….………….. Y ……………………………….………….. Z ………………………………………….. [1]

5 (ii) Suggest the trend in the melting points of elements X, Y and Z. lowest melting point …………… …………… highest melting point …………… [1] Explain your reasoning. …………………………………………………………………………………. ……………………………………………………………………………......... …………………………………………………………………………………. …………………………………………………………………………………. …………………………………………………………………………………. …………………………………………………………………………………. …………………………………………………………………………………. [3] (iii) Which of the elements, X, Y or Z, reacts with acids to form a salt? Explain your reasoning. …………………………………………………………………………………. ……………………………………………………………………………......... [1] [Total: 8] 4 The reaction between dilute hydrochloric acid and aqueous sodium hydroxide releases 57.3 kJ of energy when one mole of water is formed. (a) Write the ionic equation of the reaction. ………………………………………………………………………………………… [1] (b) (i) 200 cm3 of 0.200 mol/dm3 dilute hydrochloric acid reacts with 100 cm3 of 0.150 mol/dm3 aqueous sodium hydroxide. Calculate the overall enthalpy change of this reaction overall enthalpy change = ……………kJ [2]

6 (ii) In a separate reaction, the same volume and concentration of dilute sulfuric acid is used instead of dilute hydrochloric acid. State and explain whether this affects the overall enthalpy change of the reaction. …………………………………………………………………………………. …………………………………………………………………………………. …………………………………………………………………………………. [2] (c) Draw a labelled energy profile diagram for the reaction between dilute hydrochloric acid and aqueous sodium hydroxide. Your diagram should include: • the formulae of the reactants and products • the enthalpy change • the activation energy [3] [Total: 8] 5 Bromomethane, CH3Br, is a poisonous organic compound. It is used to kill pests such as rats and bugs. (a) Draw a ‘dot and cross’ diagram to show the bonding in bromomethane. Show the outer shell electrons only. [2]

7 (b) Determine if the following statements about bromomethane are true or false. Put a tick (ü) in one box for each statement. true false Bromomethane has a low boiling point. Bromomethane has good electrical conductivity when molten. Bromomethane could be obtained through the substitution reaction of methane and bromine. [3] (c) Bromine reacts with sodium to form sodium bromide. Draw a ‘dot and cross’ diagrams to show the arrangement of outer shell electrons in sodium bromide. [2]