GESS 3EXP CHEM EYE P2 2023

This paper consists of 19 pages including the cover page GAN ENG SENG SCHOOL End-of-Year Examination 2023 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Sec 3 Express 6092/02 6 October 2023 1 hour 45 minutes Candidates answer on the Question Paper. Calculators are allowed in the examination. READ THESE INSTRUCTIONS FIRST Write your class, index number and name 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/tape. Section A Answer all questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers 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 19. The use of an approved scientific calculator is expected, where appropriate. For Examiner’s Use Section A Section B Total 80

2 GESS 3EXP CHEM P2 EYE 2023 TKG SECTION A [70 marks] Answer ALL the questions in the spaces provided. A1 Fig. 1.1 shows part of the Periodic Table. Fig. 1.1 Select elements from Fig. 1.1 to answer the following questions. You may use each element once, more than once or not at all. Write down the atomic symbol for an element which (a) has three electrons in its valence shell, …………………………………………………………………………………….. [1] (b) is metallic and forms coloured compounds, …………………………………………………………………………………….. [1] (c) forms a basic oxide, …………………………………………………………………………………….. [1] (d) has less than 20 protons and has four electron shells, …………………………………………………………………………………….. [1] (e) is an inert gas, …………………………………………………………………………………….. [1] (f) has a giant covalent structure, …………………………………………………………………………………….. [1] (g) is a liquid at room temperature, …………………………………………………………………………………….. [1] [Total: 7]

3 GESS 3EXP CHEM P2 EYE 2023 TKG A2 Table 2.1 shows the distribution of some elements in three substances. Table 2.1 element substance oxygen iron carbon A 0% 90.4 – 95.6% 4.4 – 9.6% B 52% 48% 0% C 66.7% 0% 33.3% Identify and explain, using data from Table 2.1, which substance is a mixture. …………………………………………………………………………………………… …………………………………………………………………………………………… [2] [Total: 2] A3 Haematite, iron(III) oxide, is an iron ore that can be commonly found around the world. (a) Haematite can be reduced with carbon to form two products. Write the balanced chemical equation, with state symbols, for this reaction. …………………………………………………………………………………….. [2] (b) The reaction in (a) is said to be non -environmentally friendly. Suggest a reason why. …………………………………………………………………………………….. [1] (c) A student, Harini, commented, “Iron(III) oxide can also be obtained in the laboratory via the fast reaction between iron metal and water at 5 ºC.” Explain whether she is correct and write the chemical equation for the reaction that occurred, if any. …………………………………………………………………………………….. …………………………………………………………………………………….. [1] [Total: 4]

4 GESS 3EXP CHEM P2 EYE 2023 TKG A4 A student conducted an experiment with the apparatus set-up below. Three unknown gases, X, Y, Z and chlorine gas are compared to oxygen gas. All the porous containers are filled with oxygen gas. (a) Explain why bubbles are observed in the water for the set -ups containing gases X and Y. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. [3] (b) No bubbles were observed in the set-up containing gas Z. A small amount of water was seen to rise up the tube. Suggest a possible identity of gas Z. …………………………………………………………………………………….. [1] (c) Suggest why the gas jar containing chlorine was arranged the opposite way from the other gas jars containing gases X, Y and Z. …………………………………………………………………………………….. …………………………………………………………………………………….. [1] (d) The experiment was conducted at 25 ºC. State and explain what would be observed if the experiment was conducted at 50 ºC instead. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. [3] [Total: 8]

5 GESS 3EXP CHEM P2 EYE 2023 TKG A5 (a) Table 4.1 describes the properties of some sub-atomic particles. Complete Table 4.1. Table 4.1 relative mass relative charge proton neutron electron [2] (b) The symbol of an atom of aluminium is shown below. A𝑙13 27 (i) State the number of neutrons it has. …………………………………………………………………………….. [1] (ii) Write the electronic configuration for this atom of aluminium. …………………………………………………………………………….. [1] (iii) The symbol for another atom of aluminium is A𝑙13 26 . State and explain the relationship between these two atoms of aluminium. …………………………………………………………………………….. …………………………………………………………………………….. [1] [Total: 5]

6 GESS 3EXP CHEM P2 EYE 2023 TKG A6 A student, Yu Kai, was conducting an experiment to determine the physical properties of some substances. He recorded his results in Table 5.1 but accidentally spilled some water on a portion of his table. Table 5.1 substance melting point/ ºC boiling point/ ºC electrical conductivity solubility in water potassium chloride 770 1420 yes calcium chloride 772 1935 yes carbon 3550 4830 no no (a) Draw the ‘dot-and-cross’ diagram to show the bonding in calcium chloride. Show outer electrons only. [2] (b) Calcium chloride has a melting point of 772 ºC. (i) Explain calcium chloride’s high melting point in terms of its structure and bonding. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. [3]

7 GESS 3EXP CHEM P2 EYE 2023 TKG (ii) Suggest and explain why calcium chloride has a higher melting point than potassium chloride. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. [3] (c) Carbon can exist in different forms with different structural arrangements of its atoms. (i) State the term used to describe such different forms of carbon. …………………………………………………………………………….. [1] (ii) By referring to Table 5.1, suggest and explain which form of carbon Yu Kai likely experimented on. …………………………………………………………………………….. …………………………………………………………………………….. [2] (iii) Compare the electrical conductivity between potassium chloride and this form of carbon. Explain your answer. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. …………………………………………………………………………….. [4] [Total: 15]

8 GESS 3EXP CHEM P2 EYE 2023 TKG A7 The following reaction scheme describes some of the reaction carried out on an unknown mixture. This mixture contains three different salts.