BMSS Prelim P2

Class Index Number Name BUKIT MERAH SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 SECONDARY 4 EXPRESS CHEMISTRY 6092/02 Paper 2 15 August 2024 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. 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. 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 26. The use of an approved scientific calculator is expected, where appropriate. This document consists of 26 printed pages. Setter: Ms Jacqueline How [Turn over

2 JH/BMSS/2024/4EXP/PRELIM/6092/02 [Turn over Section A Answer all questions. 1 A list of compounds is shown. aluminium oxide calcium bromide calcium oxide ethane ethene hydrogen chloride methane nitrogen dioxide potassium iodide potassium manganate(VII) sodium chloride Answer the following questions using only the compounds in the list. Each compound may be used once, more than once or not at all. Which compound (a) when in acidified solution, is used to test for sulfur dioxide, ……………………………………………………………………………………………………………[1] (b) is the main constituent of natural gas, ……………………………………………………………………………………………………………[1] (c) when dissolved in water, gives a yellow precipitate on addition of acidified aqueous silver nitrate, ……………………………………………………………………………………………………………[1] (d) is used in industries to neutralise acidic gases, ……………………………………………………………………………………………………………[1] (e) is a reactant used in the manufacture of ethanol, ……………………………………………………………………………………………………………[1] (f) reacts with both nitric acid and potassium hydroxide to give salt and water? ……………………………………………………………………………………………………………[1] [Total: 6]

3 JH/BMSS/2024/4EXP/PRELIM/6092/02 [Turn over 2 A sample of ink contains a mixture of red, blue and yellow dyes. The chromatograms are run using a mixture of ethanol and water as solvent. Fig. 2.1 shows the graphical results of the coloured dyes of different Rf values in solvents with different proportions of ethanol. Fig. 2.1 (a) From Fig 2.1, deduce the Rf values of the blue dye on the chromatogram when the solvent is a mixture of 60cm3 of ethanol and 40cm3 of water. ……………………………………………………………………………………………………………[1] (b) The chromatography process is repeated with a filter paper when the solvent is a mixture of 20 cm3 of ethanol and 80 cm3 of water. A sample of ink was added to the middle of the filter paper. On Fig. 2.2, sketch the chromatogram results for the three coloured inks. Label your results clearly. Fig. 2.2 [2] (c) The student carried out chromatography on the ink using a different mixture of ethanol and water as solvent. There is only one spot forming on the chromatogram. Using evidence from the graph, explain why he cannot conclude that the ink is a pure substance. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………[1] [Total: 4]

4 JH/BMSS/2024/4EXP/PRELIM/6092/02 [Turn over 3 Silicon is a semiconductor. (a) Table 3.1 shows data obtained using the mass spectrum of silicon. Table 3.1 isotope relative abundance number of protons number of neutrons 28Si 92.17 29Si 4.71 30Si 3.12 (i) Complete Table 3.1 to show the number of protons and neutrons present in each isotope of silicon. [1] (ii) Calculate the relative atomic mass of silicon to two decimal places. relative atomic mass of silicon = ……………………. [1]

5 JH/BMSS/2024/4EXP/PRELIM/6092/02 [Turn over (b) Silicon dioxide, SiO2, is the main constituent of sand and has a giant lattice structure similar to that of diamond. Fig. 3.1 shows part of the structure of silicon dioxide. Fig. 3.1 Crystalline silicon dioxide is used on the surface of semiconductor devices to provide a heat-resistant, electrically insulating layer. Explain how the structure and bonding of silicon dioxide make it useful for this application. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………[3] [Total: 5]

6 JH/BMSS/2024/4EXP/PRELIM/6092/02 [Turn over 4 Lead forms two chlorides, PbCl2 and PbCl4. When chlorine is passed into a saturated solution of PbCl2 in aqueous NH4Cl, a yellow salt Y, is formed which has the following composition by mass: Cl, 46.7%; H, 1.76%; N, 6.14%; Pb 45.4% Y is ionic with a relative formula mass of 456. (a) Determine the empirical formula of Y. [2] (b) One formula unit of Y contains one type of anion and one type of cation in the ratio of 1:2. Given that Y is commonly known as ammonium hexachloroplumbate(IV), suggest the formula of each of the ions present in Y. anion: ……………………………………………………………………………………………………… cation: …………………………………………………………………………………………………..[2] (c) What is the oxidation state of Pb in Y? ……………………………………………………………………………………………………………[1] [Total: 5]

7 JH/BMSS/2024/4EXP/PRELIM/6092/02 [Turn over 5 Phosphoric acid (H3PO4) is a corrosive acid that can form three different classes of salts, namely primary phosphates, dibasic phosphates and tribasic phosphates. It dissociates in a three-step process: Step 1: 𝐻ଷ𝑃𝑂ସ(𝑎𝑞)⇌ 𝐻ଶ𝑃𝑂ସି(𝑎𝑞)+ 𝐻ା(𝑎𝑞) Step 2: 𝐻ଶ𝑃𝑂ସି (𝑎𝑞)⇌ 𝐻𝑃𝑂ସଶି(𝑎𝑞)+ 𝐻ା(𝑎𝑞) Step 3: 𝐻𝑃𝑂ସଶି(𝑎𝑞)⇌ 𝑃𝑂ସଷି(𝑎𝑞)+ 𝐻ା(𝑎𝑞) Fig. 5.1 shows the pH graph of 0.1 mol/dm3 of dilute phosphoric acid titrated with 0.1 mol/dm3 of sodium hydroxide solution (NaOH). The horizontal axis is not labelled and stage C represents the stage when the dilute phosphoric acid is fully neutralised. Fig. 5.1 (a) The horizontal axis is the percentage of the volume ratio of two reactants used. Complete the following to show how the percentage should be calculated to obtain the horizontal axis of the pH graph in Fig. 5.1. [1] (b) Write the formula of the salt formed at stage A of the titration. ……………………………………………………………………………………………………………[1]

8 JH/BMSS/2024/4EXP/PRELIM/6092/02 [Turn over (c) Table 5.1 shows three indicators and the pH where colour change takes place. Table 5.1 State which indicator can indicate the completion of stage B. Explain your answer. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………[2] [Total: 4]

9 JH/BMSS/2024/4EXP/PRELIM/6092/02 [Turn over 6 The first ionisation energy is defined as the energy required to remove the most loosely held electron in an atom to form an ion. Table 6.1 shows the first ionisation energy for the elements in Group 1. Table 6.1 element ionisation energy (MJ/mol) lithium 0.526 sodium 0.502 potassium 0.425 rubidium 0.409 caesium 0.382 (a) Based on your understanding about the reactivity of Group 1 metals, state and explain the relationship between ionisation energy and reactivity of Group 1 metals with reference to its atomic structure. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………