catholic high school chemistry paper 2 sect a prelim 2023

[Turn over Name: Index Number: Class: CATHOLIC HIGH SCHOOL Preliminary Examination Secondary 4 (O-Level Programme) CHEMISTRY 6092/02 Paper 2 22 August 2023 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. Section A Answer all questions in the spaces provided. 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. For examiner’s use only: Section A / 50 This document consists of 12 printed pages. A

2 Section A Answer all questions in this section in the spaces provided. The total mark for this section is 50. A1 The table consists of four different experimental procedures. (a) Put a tick (✓) if a redox reaction had occurred. Put a tick (✓) if a redox reaction had occurred. (i) a copper strip added to lead(II) nitrate solution (ii) aqueous chlorine added to potassium iodide solution (iii) hydrogen gas passed over heated copper(II) oxide (iv) potassium nitrate solution warmed with sodium hydroxide solution [3] (b) A student repeated (a)(ii) by replacing aqueous chlorine with aqueous bromine. Describe a difference in the rates of the two reactions and explain your answer. ……………………………………………………………………..……………………………………. ……………………………………………………………………..……………………………………. ……………………………………………………………………..……………………………………. ……………………………………………………………………………………………………..… [2] [Total: 5]

3 [Turn over A2 The boiling points of ethane and some chlorine-containing organic compounds are given in Table 2.1. Table 2.1 formula of compound C2H6 C2H5Cl C2H4Cl2 C2H3Cl3 C2H2Cl4 boiling point / °C −89 12 84 114 147 (a) Describe the general trend shown by the data in Table 2.1. ……………………………………………………………………..……………………………………. ……………………………………………………………………………………………………..… [1] (b) Use the formulae of the compounds to answer the following questions. Each formula may be used once, more than once, or not at all. (i) Which compound is a hydrocarbon? ………………..……………………………………….……………………………………… [1] (ii) Which compound belongs to the same homologous series as C4H8Cl2? ………………..……………………………………….……………………………………… [1] (c) State the total number of compounds in Table 2.1 which are soluble in organic solvents. ……………………………………………………………………………………………………..… [1] (d) Draw the displayed formulae of two isomers of C2H4Cl2. [2] [Total: 6]

4 A3 Some physical properties of five different substances are given in Table 3.1. Table 3.1 substance melting point / °C conducts electricity in the solid state? A 1410 no B 340 no C –56 no D 70 – 80 no E 2595 yes Figs. 3.1 and 3.2 show the structure of a molecule of carbon dioxide and phosphorus pentoxide respectively. Fig. 3.1 Fig. 3.2 (a) Which substance (A to E) would be carbon dioxide and phosphorus pentoxide respectively? Use ideas about structure and bonding to explain your choice. carbon dioxide ………………………… phosphorus pentoxide ………………………… ……………………………………………………………………..……………………………………. ……………………………………………………………………..……………………………………. ……………………………………………………………………..……………………………………. ……………………………………………………………………..……………………………………. ……………………………………………………………………………………………………..… [5]

5 [Turn over (b) Silicon is a semiconductor. When adequately heated, silicon can conduct electricity. Figs. 3.3 and 3.4 show the structure of silicon and graphite. Fig. 3.3 Structure of silicon Fig. 3.4 Structure of graphite (i) Compare the structure and bonding of silicon and graphite. ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………………... ………………..……………………………………………………………………….……… [2] (ii) Explain if Fig. 3.3 shows that silicon can act as a semiconductor. ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………………... ………………..……………………………………………………………………….……… [2] [Total: 9]

6 A4 (a) Photosynthesis is part of the carbon cycle. (i) Explain why photosynthesis is important in the carbon cycle. ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………….… [1] (ii) Catalytic converters do not solve all environmental problems caused by car exhausts. Explain why this is so. You should include a chemical equation in your answer. ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………….… [2] Fig. 4.1 shows the apparatus set up by a student to conduct a photosynthesis experiment in the school laboratory. Fig. 4.1 He repeated his experiment by removing the table lamp and placing the rest of the apparatus in a dark room. (b) (i) Describe a difference in the results of the two experiments. ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………….… [1] (ii) The student made a conclusion from his results: ‘Since light energy is taken in for photosynthesis to occur, it is an endothermic reaction.’ Explain why the student’s conclusion is incorrect. ………………..…………………………………………………………………………………... ………………..…………………………………………………………………………….… [1] [Total: 5] table lamp test-tube water inverted filter funnel green water plant gas X

7 [Turn over A5 Fig. 5.1 shows some reactions starting with propanol. Fig. 5.1 (a) Write a balanced chemical equation for the reaction that occurs when propanol is heated under reflux with acidified KMnO4 to form organic compound P. ……………………………………………………………………………………………………..… [1] (b) Compound R contains 64.6% carbon, 10.8% hydrogen and 24.6% oxygen by mass. (i) Determine the empirical formula of R. [2] (ii) Name compound R. ………………..…………………………………………………………………………….… [1] (c) (i) Suggest an identity for substance A. ………………..…………………………………………………………………………….… [1] (ii) Hence, give the chemical formula of ionic compound Q. ………………..…………………………………………………………………………….… [1] [Total: 6] organic compound R warm with substance B and a few drops of concentrated sulfuric acid add substance A heat under reflux with acidified KMnO4 propanol organic compound P ionic compound Q + carbon dioxide gas

8 A6 The substitution reaction of methane by chlorine is an exothermic process. (a) In terms of bond breaking and bond forming, explain why the reaction is exothermic. ……………………………………………………………………..……………………………………. ……………………………………………………………………..……………………………………. ……………………………………………………………………………………………………..… [2] (b) Chloromethane undergoes a similar substitution reaction as methane. (i) Write the chemical equation for this reaction, showing the displayed formula e of all organic compounds. [1] (ii) Suggest a value for the enthalpy change of the reaction between chlorom