Dunman (2024) 4E 6092 Prelim P2

This document consists of 28 printed pages with 1 blank page. DUNMAN SECONDARY SCHOOL CANDIDATE NAME CLASS INDEX NUMBER PRELIMINARY EXAMINATION 2024 SECONDARY 4 EXPRESS CHEMISTRY 6092/02 Paper 2 22 August 2024 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 28. The use of an approved scientific calculator is expected, where appropriate.

2 6092/02/Prelim/4Exp/2024 Section A Answer all questions. 1 These diagrams show the electron arrangement in the outer shells of five elements, A to E. All elements are from Period 2 of the Periodic Table. A B C D E Use the letters A to E to answer the following questions. You may use each letter once, more than once or not at all. (a) Which elements are most likely to be non-metals? …………….………………………………………………………………………….………...... [1] (b) Which element has an atomic number of 5? …………….………………………………………………………………………….………...... [1] (c) What element forms an ion with a charge of 2+? …………….………………………………………………………………………….………...... [1] (d) Which element will form three covalent bonds when it forms a compound? …………….………………………………………………………………………….………...... [1] (e) Which two elements will form a compound with the formula of the type YZ2? …………….………………………………………………………………………….………...... [1] [Total: 5]

3 6092/02/Prelim/4Exp/2024 2 Table 2.1 shows the formulae of some oxides of elements from period 3 of the Periodic Table. Table 2.1 Group 1 2 13 14 15 16 17 Na2O MgO Al2O3 SiO2 P2O5 SO2 Cl2O (a) From the table give one formula each for acidic oxide, basic oxide and amphoteric oxide. acidic oxide ………………………. basic oxide ………………………. amphoteric oxide ………………........... [2] (b) Draw a ‘dot-and-cross’ diagram to show the bonding in sulfur dioxide. Show outer electrons only. [2]

4 6092/02/Prelim/4Exp/2024 (c) Explain, in terms of structure and bonding, why the melting point of silicon dioxide is very much higher than that of sulfur dioxide. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ...……………………………………………………………………………………………….… [3] (d) Dichlorine monoxide melts at - 120˚C and boils at 2˚C. Describe the changes in the movement and arrangement of the particles as it is heated from 0˚C to 20˚C. movement …………………………………………………………………………………………. ………………………………………………………………………………………………………. arrangement ………………………………………………………………………………………. ...……………………………………………………………………………………………….… [2] (e) Dichlorine monoxide dissolves in water to produce hypochlorous acid. Cl2O (g) + H2O (l) ⇌ 2HOCl (aq) Explain why dichlorine monoxide is a poor conductor of electricity, while hypochlorous acid is a good conductor of electricity. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ...……………………………………………………………………………………………….… [2] [Total: 11]

5 6092/02/Prelim/4Exp/2024 3 The table shows information about the preparation of pure samples of solid salts. Complete the table by filling in the missing information, including state symbols with any formulae. formula of salt formulae of reagents used method used MgCl2 (aq) ……………………….. HCl (aq) addition of excess solid to acid filtration evaporation and crystallisation ………………….. NH3 (aq) H2SO4 (aq) ………………………………………………. evaporation and crystallisation BaCO3 (s) ………………………… ………………………… ……………………………………………..… ……………………………………………….. [5] [Total: 5]

6 6092/02/Prelim/4Exp/2024 4 Rocket belts can be used to lift people into the air and transport them over short distances. The picture below shows a rocket belt, usually strapped onto a person’s back. Rocket belts contain concentrated hydrogen peroxide solution as a fuel. An exothermic change occurs when the hydrogen peroxide decomposes rapidly to form oxygen and water. The reaction is shown below: 2H2O2 → 2H2O + O2 The rapid releases of oxygen from the jetpack lifts the person off the ground. (a) Explain, in terms of bond breaking and bond making, why the reaction is exothermic. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ...……………………………………………………………………………………………….… [2] (b) The decomposition of hydrogen peroxide is very slow at room temperature. In a rocket belt, silver powder is present to make the decomposition reaction much faster. The silver powder remains unchanged at the end of the reaction. (i) State the role of silver powder in the decomposition of hydrogen peroxide. ……………………………………………………………………………………………. [1]

7 6092/02/Prelim/4Exp/2024 (ii) Complete the energy profile diagram to show the effect of silver powder on the decomposition of hydrogen peroxide. Your diagram should include: • reactants and products, • the activation energy for the reactions with and without silver powder, • the enthalpy change of the reaction. [3] [Total: 6] Energy (kJ) Progress of reaction

8 6092/02/Prelim/4Exp/2024 5 Sodium sulfite (Na2SO3) is often added to preserve food. The amount of sodium sulfite in a piece of meat can be determined through a series of tests shown below. Step 1: Boil the meat with hydrochloric acid to form sodium chloride, water and sulfur dioxide. Step 2: Collect gas produced and bubble it through 100 cm3 of water to dissolve sulfur dioxide. Step 3: Titrate the solution obtained against iodine according to the following reaction. SO2 (g) + 2H2O (l) + I2 (aq) → 4H+ (aq) + SO42- (aq) + 2I- (aq) (a) Describe a chemical test to determine if there is any sulfur dioxide remaining after the gas has been bubbled through water in step 2. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ...……………………………………………………………………………………………….… [2] (b) It was noted that 12.00 cm3 of 0.025 mol/dm3 of iodine was required for complete reaction in the titration. Assume all the gas has dissolved in water. (i) Calculate the volume of SO2 produced in step 2. Show your working. [2]

9 6092/02/Prelim/4Exp/2024 (ii) Explain, in terms of oxidation states, why the titration in s tep 3 involves a redox reaction. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………. [2] [Total: 6]

10 6092/02/Prelim/4Exp/2024 6 ‘Lean burn’ engines are a type of car engine. Table 6.1 shows some information about learn burn engines compared to normal car engines. Table 6.1 type of engine amount of air mixed with petrol operating temperature normal less air higher lean more air lower The amount of air that is mixed with p etrol and t