SNGS 2024 Sec 4 Prelim P2 QP

1 Name: _________________________ ( ) Class: ___________ PRELIMINARY EXAMINATION GENERAL CERTIFICATION OF EDUCATION ORDINARY LEVEL CHEMISTRY 6092/02 Paper 2 19 August 2024 1 hour 45 minutes ____________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Write your name, register number, and class clearly in the spaces provided at the top of this page. Write in dark blue or black pen only. You may use a soft pencil for any diagrams or graphs. Do not use highlighters, glue, and correction fluid or correction tape. Section A Answer all questions in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. A copy of Periodic Table is provided on page 22. The number of marks is given in brackets [ ] at the end of each question or part question. The use of a scientific calculator is expected, where appropriate. For Examiner’s Use Section A (70) Section B (10) Total (80) ____________________________________________________________________________ This document consists of 22 printed pages and 1 blank page. [Turn over

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3 Section A Answer all questions. 1 Use the list of substances to answer the questions. SO2 CO NH3 ZnO NO2 K2O Each substance can be used once, more than once or not at all. (a) Which covalent substance has a boiling point lower than poly(ethene) but higher than oxygen? Explain your answer in terms of bonding and structure. …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... [3] (b) Which substance can be used to make fertilizers? …………………………………………………………………………………... [1] (c) Which substance can react with both aqueous sodium hydroxide and hydrochloric acid to form salts? …………………………………………………………………………………... [1] (d) Which substance can reduce copper(II) oxide to copper? ………………………………………………………………………………….. [1] (e) Which substance consists an element with an oxidation state of -3? …………………………………………………………………………………... [1] (f) Which substance, in aqueous solution, has the highest pH? …………………………………………………………………………………... [1] [Total: 8 marks]

4 2 The following information was found on a 100PLUS can: (a) Suggest the formula of a positive ion which is found in 100PLUS, but not listed in the table above. Describe a simple test to confirm the presence of this ion. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. [2] (b) A student wanted to prepare a sample of potassium phosphate. Suggest the reagents and method used to prepare aqueous potassium phosphate. ………………………………………………………………………………………. ………………………………………………………………………………………. [2]

5 (c) Describe a test that can be carried out to show the presence of chloride ions in 100PLUS. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ………………………………………………………………………………………… [2] (d) Besides sodium chloride, there are other sodium compounds present in 100PLUS. Using the information given in the table, show by calculation that this is true. [2] (e) The energy which a can (serving) of 100PLUS provides comes from the breaking down of the carbohydrates (sucrose and glucose) in our bodies. This can be represented by the unbalanced equation: CxHyOz + O2 → CO2 + H2O Draw an energy profile diagram of the above reaction. Label clearly the reactants and products, enthalpy change and activation energy of the reaction. [3]

6 (f) Ethanol can be produced using 100PLUS as the starting reagent. This reaction is like the process of obtaining bioethanol from glucose in sugarcane. (i) List the conditions and state what must be added for this reaction to occur. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] (ii) Write three chemical equations to explain why bioethanol is considered environmentally sustainable. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] [Total: 15 marks]

7 3 Sulfuric acid, which is used in the manufacture of detergents and fertilisers, is a strong dibasic acid that can be manufactured industrially through the Contact Process. The steps below show the reactions taking place during the Contact Process. Stage I : S (s) + O2 (g) SO2 (g) Stage II : 2SO2 (g) + O2 (g) ⇌ 2SO3 (g) Stage III: SO3 (g) + H2SO4 (l) H2S2O7 (l) Stage IV: H2S2O7 (l) + H2O (l) 2H2SO4 (aq) (a) Which stage of the process is the pressure least likely to affect the rate of reaction? ……………………………………………………………………………………. [1] (b) Stage II occurs in the presence of the catalyst vanadium (V) oxide. A student thinks that the catalyst reduces the activation energy for the reaction and therefore the enthalpy change of the reaction is lower. Do you agree? Explain your answer. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… [2] (c) Which of the reactions above are redox reactions? Explain your answer in in terms of oxidation state. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… [2] (d) The percentage yield for the production of sulfuric acid from sulfur is only 30 %. Based on the information above, explain why. …………………………………………………………………………………… ……………………………………………………………………………………. [1]

8 (e) Write the overall chemical equation for Stage I to Stage IV. …………………………………………………………………………………… [1] (f) The emissions from a power station contain a significant amount of sulfur dioxide. It is produced due to the combustion of coal that contains sulfur. This reaction is the same as Stage I in the Contact Process. Sulfur dioxide can cause acid rain. (i) State another pollutant that cause s acid rain and describe how this pollutant is formed. ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… [2] (ii) Using a suitable ionic equation, explain the effect of acid rain on buildings containing zinc structures or limestone. ……………………………………………………………………………… [1] (iii) Suggest one substance which can be used to reduce the effects of acid rain on water bodies without leaving behind an alkaline solution. ……………………………………………………………………………… [1] (iv) State one harmful effect of sulfur dioxide on humans. ………………………………………………………………………………. [1] [Total: 12 marks] [Total: 7 marks]

9 4 1,2-dichloropentanol can be synthesized from pent-1-ene using suitable reagents and conditions. The structures of these organic compounds are given below. Cl Cl H H H H H H H H I I I I I