Dunman 2026 S4 Pure Chem 6092 Prelim P2

This document consists of 23 printed pages and 1 blank page. DUNMAN SECONDARY SCHOOL CANDIDATE NAME CLASS INDEX NUMBER PRELIMINARY EXAMINATION 2026 SECONDARY 4 EXPRESS CHEMISTRY 6092/02 Paper 2 26 August 2026 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. 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. 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 23. The use of an approved scientific calculator is expected, where appropriate.

2 6092/02/Prelim/4Exp/2026 Section A Answer all questions. 1 The formulae of some ions are shown below. Al3+ Ag+ Ca2+ Cl- CO3 2- H+ H- I- K+ Li+ OH- O2- Fill in the blanks with the formulae of the correct ion(s). Each formula may be used once, more than once, or not at all. (a) a cation which has the same arrangement of electrons as neon, Formula of ion : ……………………. (b) an anion which has only two electrons, Formula of ion : ……………………. (c) ions which react together to produce a gas which gives a white precipitate in limewater, Formulae of ions: …………………… and ……….………...... (d) ions responsible for the formation of a yellow precipitate when aqueous silver nitrate is added to aqueous solution of a sodium salt, Formulae of ions: …………………… and ……….………...... (e) ions responsible for the formation of a white precipitate which remained unchanged when aqueous sodium hydroxide was added in excess to an aqueous nitrate. Formulae of ions: …………………… and ……….………...... [Total: 5]

3 6092/02/Prelim/4Exp/2026 2 Graphene and diamond are allotropes (different forms) of carbon. Stacked layers of graphene form graphite. Fig. 2.1 shows structures of graphene and diamond. graphene diamond Fig. 2.1 (a) Describe the similarities and differences between the bonding and structure in graphene and diamond. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ………………………….……………………………………………………………………………. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………. [3]

4 6092/02/Prelim/4Exp/2026 (b) When graphene and diamond are heated in air, both allotropes combust to produce carbon dioxide. The solubility of graphene, diamond and carbon dioxide in water are shown in the table. graphene diamond carbon dioxide solubility in water insoluble insoluble soluble to form a weakly acidic solution Use your knowledge of structure and bonding to explain the difference in solubility between graphene, diamond and carbon dioxide. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………….............................................................................................................. ……………………………………………………………………………………………….………. ………………......................................................................................................................... ......................................................................................................................................... [3] [Total: 6]

5 6092/02/Prelim/4Exp/2026 3 Suggest explanations for the following observations: (a) When dilute sulfuric acid is exactly neutralised by aqueous potassium hydroxide, the resulting mixture is a good conductor of electricity but when the same acid is exactly neutralized by aqueous barium hydroxide, the resulting mixture is a very poor conductor of electricity. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ………………......................................................................................................................... ......................................................................................................................................... [2] (b) When dilute hydrochloric acid and dilute sulfuric acid are electrolysed separately using inert electrodes, the ratio of the volume of gases obtained at the cathode and anode is 2:1. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ………………......................................................................................................................... ......................................................................................................................................... [2] [Total: 4]

6 6092/02/Prelim/4Exp/2026 4 Lead(II) iodide salt may be made by the reaction between aqueous potassium iodide and aqueous lead(II) nitrate. A student added 50 cm3 of 1.0 mol/dm3 potassium iodide to 50 cm3 of 1.0 mol/dm3 lead(II) nitrate. 2KI(aq) + Pb(NO3)2(aq) → 2KNO3(aq) + PbI2(s) (a) Name this method of salt preparation. …………………………………………………………………………………………………..…… [1] (b) The experiment yielded x g of lead(II) iodide. The student did another experiment to make lead(II) chloride by adding 50 cm3 of 1.0 mol/dm3 potassium chloride to 50 cm3 of 1.0 mol/dm3 lead(II) nitrate. Compare the amount of lead(II) chloride with the amount of lead(II) iodide. Explain your answer. ………………………………………………………………………………………………………….. …..……………………………………………………………………………………….……..…… [1] (c) Potassium nitrate is also a product of the reaction between aqueous potassium iodide and aqueous lead(II) nitrate. (i) Explain why the student’s method is not suitable for obtaining a pure sample of potassium nitrate. ………………………………………………………………………………………..………… …………………………………………………………………………………….………… [1] (ii) By naming a suitable pair of reagents, suggest how potassium nitrate can be prepared. …………………………………………………………………………………………….… [1] [Total: 4]

7 6092/02/Prelim/4Exp/2026 5 Zinc reacts slowly with dilute sulfuric acid. In order to speed up the reaction, aqueous copper(II) sulfate was added to a mixture of zinc and dilute sulfuric acid. The result is a displacement of copper metal which catalyses the reaction between zinc and dilute sulfuric acid. The graph below shows the volume of hydrogen gas obtained when various volumes of 1.0 mol/dm3 aqueous copper(II) sulfate were added to mixtures of the same mass of zinc and excess dilute sulfuric acid. Fig. 5.1 (a) With reference to the graph, state the volume of hydrogen gas that would have been formed if the following solutions were added: (i) 4 cm3 of 1.0 mol/dm3 copper(II) sulfate …………………………………………….. (ii) 10 cm3 of 1.0 mol/dm3 copper(II) sulfate …………………………………………….. (iii) 2 cm3 of 3.0 mol/dm3 copper(II) sulfate …………………………………………….. [3] 0 2 4 6 8 10 volume of 1.0 mol/dm3 aqueous copper(II) sulfate added/cm3 200 150 100 50 0 total volume of hydrogen gas formed/cm3

8 6092/02/Prelim/4Exp/2026 (b) State and explain the relationship between the volume of hydrogen formed and the volume of copper(II) sulfate added. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………. [2] (c) Suggest two other ways to speed up the reaction between zinc and dilute sulfuric acid which