2024 H1 Prelim Paper 2 HCI

This document consists of 20 printed pages and 0 blank page. © Hwa Chong Institution 8873/02/Prelim 2024 [Turn over HWA CHONG INSTITUTION C2 Preliminary Examination Higher 1 CANDIDATE NAME CT GROUP 23S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 2 Structured Questions Candidates answer on the Question Paper Additional Materials: Data Booklet 8873/02 11 September 2024 2 hours READ THESE INSTRUCTIONS FIRST Write in dark blue or black pen. You may use a 2B pencil for any diagrams or graphs. Do not use staples, paper clips, glue, correction fluid or tapes. Section A Answer all the questions. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. FOR EXAMINERS’ USE ONLY Number of additional writing paper(s) submitted Paper 2 Section A 1 / 14 2 / 17 3 / 10 4 / 19 Paper 2 Section B 5 or 6 / 20 Paper 2 / 80 Paper 1 / 30 Total / 100

2 © Hwa Chong Institution 8873/02/Prelim 2024 [Turn over Section A Answer all the questions in this section in the spaces provided. 1 Use of Data Booklet is relevant to this question. Tellurium is an element with an electronic configuration of [Kr] 4d10 5s2 5p4. The most common isotope of tellurium is 130Te. (a) Complete Table 1.1. Table 1.1 number of neutrons number of electrons 130Te [1] (b) Describe how the behaviour of beams of 130Te+ ion, 130Te atom and the electron, e−, differ in an electric field. ………………………………………………………………………………………………..…..... ………………………………………………………………………………………………..…..... ………………………………………………………………………………………………..…..... ………………………………………………………………………………………………..…..... ………………………………………………………………………………………………..…..... ……………………………………………………………………….………………............… [2] (c) (i) Write an equation to represent the first ionisation energy of Te. ……………………………………………………………………….………………...… [1] (ii) State and explain the general trend in first ionisation energy across period 3. …………………………………………………………………………..…………………... ………………………………………………………………………..……………………... ………………………………………………………………………..……………………... ……………………………………………………………………….………………...… [2] (iii) Suggest why tellurium may not follow the general trend in (c)(ii). ………………………………………………………………………..……………………... ……………………………………………………………………….………………...… [1]

3 © Hwa Chong Institution 8873/02/Prelim 2024 [Turn over (d) (i) Sketch a graph in Fig. 1.1 to show the trend in the first seven ionisation energies of Te. Fig. 1.1 [2] (ii) Explain why the radius of Te ions decreases after each successive ionisation. ………………………………………………………………………..……………………... ……………………………………………………………………….………………...… [1] (e) Te reacts with F2 at 150 °C to form TeF6. Molecules of TeF6 are octahedral. Using the Valence Shell Electron Pair Repulsion theory, explain why TeF6 is octahedral. ………………………………………………………………………………………………..…..... ………………………………………………………………………………………………..…..... ……………………………………………………………………….………………............… [2] (f) TeF6 reacts with water to form tellurium hydroxide and HF. The oxidation number of tellurium does not change during this reaction. (i) Construct an equation for the reaction of TeF6 with water. ……………………………………………………………………….………………...… [1] (ii) Name the type of reaction that occurs when TeF6 reacts with water. ……………………………………………………………………….………………...… [1] [Total: 14]

4 © Hwa Chong Institution 8873/02/Prelim 2024 [Turn over 2 Some common chlorides of Period 3 elements are shown in the list. NaCl MgCl2 AlCl3 SiCl4 PCl5 (a) From this list, identify all the chlorides that: (i) have giant ionic structures in the solid state. ……………………………………………………………………….………………...… [1] (ii) cause vigorous effervescence when added to aqueous sodium carbonate. ……………………………………………………………………….………………...… [1] (b) Sulfur, S8, reacts with chlorine to form several different chlorides. The most common are S2Cl2 and SCl2. SCl2 forms when sulfur reacts with excess chlorine. reaction 1 S8(s) + 4Cl2(g) → 4S2Cl2(l) ΔHr = −58.2 kJ mol−1 reaction 2 S2Cl2(l) + Cl2(g) 2SCl2(l) ΔHr = −40.6 kJ mol−1 (i) Fig. 2.1 shows the structures of S8 and S2Cl2 in reaction 1. Fig. 2.1 Using relevant values in the Data Booklet, the enthalpy change of reaction for reaction 1 and the structures in Fig 2.1, calculate the bond energy of S−Cl. [3] (ii) Define the standard enthalpy change of formation, ΔHf. ………………………………………………………………………..……………………... ……………………………………………………………………….………………...… [1]

5 © Hwa Chong Institution 8873/02/Prelim 2024 [Turn over (iii) Calculate the standard enthalpy change of formation of SCl2(l), ΔHf, using the enthalpy changes of reactions 1 and 2 and the energy cycle in Fig. 2.2. S8(s) + 4Cl2(g) 4S2Cl2 (l) +4Cl2(g) +4Cl2(g) 8SCl2(l) Fig. 2.2 enthalpy change of formation of of SCl2(l), ΔHf = ……………………………kJ mol−1 [3] (c) (i) Explain why reaction 2 is a redox reaction. Include oxidation numbers in your answer. ………………………………………………………………………..……………………... ………………………………………………………………………..……………………... ……………………………………………………………………….………………...… [2] (ii) When oxidation and reduction occur, there is a movement of electrons. The unit of charge is the coulomb, C. The charge on an electron is −1.60 x 10−19 coulombs. Calculate the charge transferred, in coulombs, when 1.5 moles of chlorine molecules react with S2Cl2 in reaction 2. charge transferred = …………………………… coulombs [2]

6 © Hwa Chong Institution 8873/02/Prelim 2024 [Turn over (iii) State the effect of increasin g pressure on the position of equilibrium and the equilibrium constant of reaction 2. Explain your answer. ………………………………………………………………………..……………………... ………………………………………………………………………..……………………... ……………………………………………………………………….………………...… [2] (iv) Deduce whether SCl2 is a polar molecule. Explain your answer. ………………………………………………………………………..……………………... ……………………………………………………………………….………………...… [2] [Total: 17] 3 In industry, different processes are used to manufacture several types of polyethene, each with a different structure. The polymer chains shown in Fig. 3.1 are simplified representations of the actual structures. low-density polyethene (LDPE) linear low-density polyethene (LLDPE) Fig. 3.1 LLDPE is made by mixing other alkenes with ethene before polymerisation. This introduces short side chains into the main polymer chain. (a) LDPE and LLDPE are used in building materials, packaging and hot drinks containers. Explain why the tensile strength of LDPE is lower than LLDPE. ………………………………………………………………………………………………..…..... ………………………………………………………………………………………………..…..... ………………………………………………………………………………………………..…..... ………………………………………………………………………………………………..…..... ………………………………………………………………………………………………..…..... ……………………………………………………………………….………………............… [1]

7 © Hwa Chong Institution 8873/02/Prelim 2024 [Turn over (b) Fig. 3.2 shows the structure of a part of a chain of LLDPE. Fig. 3.2 Complete the table below by drawing and naming the two alkenes that have been mixed with ethene molecules to make the polymer shown in Fig 3.2. Two alkenes other than ethene Alkene 1 Alkene 2 Skeletal formula Name propene [3] (c) Use of the Data Booklet is relevant to this question. Suggest how the infrared (IR) spectrum of polyvinyl chloride (PVC) would differ from polyethene. ……………………………………………………………………….………………............… [1]

8 © Hwa Chong Institution 8873/02/Prelim 2024 [Turn over (d) Polyurethanes are polymers made by the re