SJI 2024 Y4 Prelim Chemistry Paper 2

ST. JOSEPH’S INSTITUTION PRELIMINARY EXAMINATION 2024 (YEAR 4) CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Candidates answer on the Question Paper. No Additional Materials are required. 6092/02 14 August 2024 1 hour 45 minutes (11:50 – 13:35) READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Write in dark blue or black fluid ink pen. You may use a soft pencil for any diagrams, graphs or rough working. 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. The use of an approved scientific calculator is expected, where appropriate. A copy of the Periodic Table is printed on page 2. For Examiner’s Use Section A / 70 Section B / 10 Total / 80 This document consists of 26 printed pages.

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3 Section A Answer all questions. 1 Select elements from the list to answer the following questions. You may use each element once, more than once or not at all. argon iodine neon chlorine iron sodium hydrogen lithium zinc (a) Which element shows both metallic and non-metallic character? ……………….…………………………………………………………………………..[ 1] (b) Which element, other than iron, is used in the manufacture of steel? ……………….…………………………………………………………………………..[1] (c) Which element gives a reddish-brown solution when added to aqueous potassium bromide? ……………….…………………………………………………………………………..[1] (d) Which two elements react together most vigorously? ……………….…………………………………………………………………………..[1] (e) (i) Which elements, when separately added to aqueous copper( II) nitrate, will cause a gas to be formed? ………………..……………………................................................................[ 1] (ii) For one of the elements in (e)(i), write a chemical equation for the formation of the gas. ………………..……………………................................................................[ 1] [Total: 6]

4 2 (a) A reaction in which the same element is both oxidised and reduced is called a disproportionation reaction. The reaction between chlorine and hydroxide ions is shown below. 3Cl2 + 6OH- → 5Cl- + ClO3- + 3H2O Use oxidation states to explain why this reaction is a disproportionation reaction. ..………………..…………………………………………………………………………… ..………………..…………………………………………………………………………… ..………………..…………………………………………………………………………… ……………….…………………………………………………………………………..[2] (b) 1.0 g samples of two oxochlorides, Si2OCl6 and Si3O2Cl8, are separately reacted with excess water, during which all the chlorine atoms are converted into chloride ions. The chloride ions are precipitated out using excess aqueous silver nitrate, and the precipitates are dried and weighed. By calculating the amount , in moles, of chloride ions formed when each oxochloride is reacted with excess water, deduce which of the two oxochlorides would form the larger mass of precipitate. [3] [Total: 5]

5 3 Table 3.1 shows vehicle emissions from cars with different types of engines. Table 3.1 engine type carbon dioxide / arbitrary units carbon monoxide / arbitrary units electric 10 22 hybrid (electric and petrol) 50 176 diesel 160 408 petrol 120 221 (a) Using the information provided, determine which engine type causes most harm to the environment. ..………………..…………………………………………………………………………… ………………….………………………………………………………………………..[ 1] (b) (i) Describe how carbon monoxide is formed in car engines. ……………..………………………………………………………………………… ………………..……………………................................................................[ 1] (ii) Cars are fitted with catalytic convertors. Explain how catalytic convertors remove harmful pollutants like carbon monoxide. Include relevant equations to support your answer. ……………..………………………………………………………………………… ……………..………………………………………………………………………… ……………..………………………………………………………………………… ……………..………………………………………………………………………… ………………..……………………................................................................[ 3]

6 (c) Governments are increasingly encouraging the use of electric vehicles to reduce carbon dioxide emissions. Explain why reducing carbon dioxide emissions is of global importance. ..………………..…………………………………………………………………………… ..………………..…………………………………………………………………………… ..………………..…………………………………………………………………………… ………………….………………………………………………………………………..[2] [Total: 7]

7 4 The alcohols are a homologous series. Table 4.1 shows some data about the enthalpy change when 1 mol of each alcohol is completely combusted. Table 4.1 name of alcohol formula enthalpy change of combustion / kJ/mol methanol CH3OH -715 ethanol CH3CH2OH -1371 propan-1-ol CH3CH2CH2OH butan-1-ol CH3CH2CH2CH2OH -2673 (a) Ethanol can be made from either ethene or glucose. (i) The reaction for the formation of ethanol from ethene is shown below. C2H4 + H2O → CH3CH2OH State the conditions under which this reaction takes place. ………………..……………………................................................................[ 1] (ii) Explain why ethanol made from ethene is a non -renewable fuel but that made from glucose is a renewable fuel. ……………..………………………………………………………………………… ……………..………………………………………………………………………… ………………..……………………................................................................[ 1] (b) The enthalpy change when 4.0 g of propan-1-ol is burnt is -134 kJ. Calculate the enthalpy change of combustion of propan-1-ol in kJ/mol. Show your working. [1]

8 (c) The enthalpy change of combustion becomes more negative from methanol to butan-1-ol. Use ideas about breaking and forming bonds to explain why. ..………………..…………………………………………………………………………… ..………………..…………………………………………………………………………… ..………………..…………………………………………………………………………… ..………………..…………………………………………………………………………… ……………….…………………………………………………………………………..[2] Table 4.2 shows some information about three isomers , butan-1-ol, butan -2-ol and diethylether. Table 4.2 butan-1-ol butan-2-ol diethylether structural formula enthalpy change of combustion / kJ/mol -2673 -2732 (d) (i) State the molecular formula of diethylether. ………………..……………………................................................................[1] (ii) Molecules of diethylether are symmetrical and contain a C –O–C functional group. Draw the full structural formula of diethylether. [1]

9 (e) The same products are formed when each of the three isomers in Table 4.2 are completely combusted. However, the enthalpy change of combustion of butan -1-ol (-2673 kJ/mol) is less negative than that of diethylether (-2732 kJ/mol). (i) Suggest a reason why the enthalpy changes of combustion for butan -1-ol and diethylether are different. ……………..………………………………………………………………………… ………………..……………………................................................................[ 1] (ii) Hence, suggest a value for the enthalpy change of combustion of butan-2-ol. ………………..……………………................................................................[ 1] [Total: 9]

10 5 A student carried out some experiments using the metals iron, manganese and chromium. He added the metals into dilute sulfuric acid. He also heated the metals in air. Table 5.1 shows his observ