Copy of ACSBR 6092 Sec 4 Prelims 2024 P2

Name Class Index Number Anglo-Chinese School (Barker Road) PRELIMINARY EXAMINATION 2024 SECONDARY FOUR EXPRESS CHEMISTRY 6092/2 TIME: 1 HOUR 45 MINUTES INSTRUCTIONS TO CANDIDATES: Do not open this booklet until you are told to do so. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Sections A Answer all questions. Write your answers in the spaces provided. Sections 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. The use of an approved scientific calculator is expected, where appropriate. A copy of the Periodic Table is printed on the last page. FOR EXAMINER’S USE ONLY Section A / 70 Section B / 10 Total Score / 80

Anglo-Chinese School (Barker Road) Preliminary Examination 2024 Secondary 4 Express Chemistry 6092/2 2 This paper consists of 23 printed pages including the cover page and a blank page. Section A (70 marks) Answer all questions. A1 The formulae of some ions are given in the following list. Ca2+ Cl− Li+ Na+ O2− (a) Choose ions from the list to answer the questions. You may use each ion once, more than once, or not at all. (i) Which ion has only two electrons? ……….……………………………………………………………………………………... [1] (ii) Which ions have the same arrangement of electrons as argon? ……….……………………………………………………………………………………... [1] (iii) Which two ions bond to form a compound which has the highest melting point? ……….……………………………………………………………………………………... [1] (b) What do you observe when aqueous bromine is added to aqueous Cl− ions? Explain your reasoning. …...……….……………………………………………………………………………………….. …...……….……………………………………………………………………………………….. …...……….……………………………………………………………………………………….. …...……….……………………………………………………………………………………….. [2] [Total: 5]

Anglo-Chinese School (Barker Road) Preliminary Examination 2024 Secondary 4 Express Chemistry 6092/2 3 A2 The structures of ethanoic acid and ethanoyl chloride are shown below. ethanoic acid ethanoyl chloride Both compounds react with methanol to make the same ester. (a) Name and draw the full structural formula of the ester. name of ester: ………………………………………………………………………………….. [2] (b) Complete Table 2.1 to show the formula of the other product of each reaction. Table 2.1 formula product formed from the reaction with ethanoic acid product formed from the reaction with ethanoyl chloride [2] [Total: 4]

Anglo-Chinese School (Barker Road) Preliminary Examination 2024 Secondary 4 Express Chemistry 6092/2 4 A3 Hydrogen peroxide, H2O2, is often used as a bleach and antiseptic, usually as a dilute solution for consumer use and in higher concentrations for industrial use. (a) Hydrogen peroxide solution has to be freshly prepared as it decomposes to form water and oxygen gas under normal room conditions. The equation shows the decomposition of hydrogen peroxide. 2H2O2 ⟶ 2H2O + O2 (i) Why is hydrogen peroxide solution usually put into the refrigerator after preparation? ……….……………………………………………………………………………………... ……….……………………………………………………………………………………... [1] (ii) The peroxide ion has the formula O22-. It has a single bond between the two oxygen atoms. Draw a ‘dot-and-cross’ diagram to show the arrangement of electrons in a peroxide ion. Show outer electrons only. [2] (b) Hydrogen peroxide can be prepared by various methods. Hydrogen peroxide was once prepared using ammonium persulfate, (NH4)2S2O8. Deduce the formula of the persulfate ion. …………...…………………………………………………………………………………..…… [1]

Anglo-Chinese School (Barker Road) Preliminary Examination 2024 Secondary 4 Express Chemistry 6092/2 5 (c) Another method of prepar ing hydrogen peroxide bleach involves Group 1 metal peroxides reacting with water to form Group 1 metal hydroxides and hydrogen peroxide. (i) Write a chemical equation for the reaction of sodium peroxide, Na2O2, with water. State symbols are not required. ……….……………………………………………………………………………………... [1] (ii) When a solution of red litmus indicator is added to the reaction mixture in (c)(i), the solution turns colourless. One student makes this statement about the observation. Paul: “The solution should have turned blue.” Does the information support the statement made by Paul? Explain your reasoning. ……….……………………………………………………………………………………... ……….……………………………………………………………………………………... ……….……………………………………………………………………………………... ……….……………………………………………………………………………………... [2] (d) Hydrogen peroxide can react with sulfuric acid to form highly reactive oxygen atoms as shown. H2SO4 + H2O2 ⟶ HSO4 − + H3O+ + O These oxygen atoms can then react with the carbon impurity, which is usually unreactive to most aqueous solutions at room temperature. The final product of the reaction between carbon and oxygen atoms is a greenhouse gas. (i) Write the chemical equation for the reaction between carbon and oxygen atoms. State symbols are not required. ……….……………………………………………………………………………………... [1] (ii) Describe the potential environmental effects of increased levels of greenhouse gases. ……….……………………………………………………………………………………... ……….……………………………………………………………………………………... ……….……………………………………………………………………………………... [1] [Total: 9]

Anglo-Chinese School (Barker Road) Preliminary Examination 2024 Secondary 4 Express Chemistry 6092/2 6 A4 Butane is a gaseous fuel commonly used in aerosol cans and for domestic cooking. (a) Draw the energy profile diagram for the combustion of butane. Your diagram should show: • the balanced chemical equation, • the enthalpy change of reaction, ΔH, and • the activation energy, Ea, of the reaction. [4] (b) When burnt, it releases 120 kJ for every 1 dm3 of butane used at room temperature and pressure. Calculate the energy released when 1 mole of butane is allowed to undergo complete combustion. [1] (c) Butane gas is made from crude oil and burning it produces air pollutants. State another disadvantage of using butane as a fuel. …………….………………………………………………………………………………………. ...…….…….………………………………………………………………………………………. [1]

Anglo-Chinese School (Barker Road) Preliminary Examination 2024 Secondary 4 Express Chemistry 6092/2 7 (d) Explain, in terms of collisions, why a lower pressure decreases the rate of combustion of butane. ...…….…….………………………………………………………………………………………. ...…….…….………………………………………………………………………………………. ...…….…….………………………………………………………………………………………. ...…….…….………………………………………………………………………………………. [2] (e) Propane is a more popular choice of fuel than butane for portable stoves used during barbecues because of its lower boiling point than butane . This makes propane able to retain its ability to vaporise even in cold weather. Use ideas about structure and bonding to explain why the boiling point of propane is lower than the boiling point of butane. ...…….…….………………………………………………………………………………………. ...…….…….………………………………………………………………………………………. ...…….…….………………………………………………………………………………………. ...…….…….………………………………………………………………………………………. [2] [Total: 10]

Anglo-Chinese School (Barker Road) Preliminary Examination 2024 Secondary 4 Express Che