2022 EFSS Chem Prelims P2

EDG/PRELIM22/CHEM/6092/02/4EXP/BN [Turn over Class: Candidate Name: Candidate Index Number: EDGEFIELD SECONDARY SCHOOL 2022 PRELIMINARY EXAMINATION Secondary 4 O Syllabus CHEMISTRY Paper 2 Theory Candidates answer on the Question Paper. No Additional Materials are required. 6092/02 August 2022 1 hour 45 minutes READ THESE INSTRUCTIONS FIRST Write your class, name and class register number in the above boxes. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions in the spaces provided. Section B Answer all three questions, the last question is in the form either/or. Answer all questions in the spaces provided. At the end of the examination, fasten all your work securely together. 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 22. The use of an approved scientific calculator is expected, where appropriate. FOR EXAMINER’S USE My target grade/mark: _________ Section A / 50 Section B / 30 TOTAL / 80 Parent’s signature This document consists of 22 printed pages.

EDG/PRELIM22/CHEM/6092/02/4EXP/BN 2 Section A Answer all questions in this section in the spaces provided. The total mark for this section is 50. A1 Choose from the following equations to answer the questions below. A CO32−(aq) + 2H+(aq) → CO2(g) + H2O(l) B Cu(s) → Cu2+(aq) + 2e− C Cu2+(aq) + 2e− → Cu(s) D Cu2+(aq) + 2OH−(aq) → Cu(OH)2(s) E Fe(s) + 2H+(aq) → Fe2+(aq) + H2(g) F H+(aq) + OH−(aq) → H2O(l) G 2I−(aq) + Br2(aq) → I2(aq) + 2Br−(aq) H NH4+(aq) + OH−(aq) → H2O(l) + NH3(g) I 4OH−(aq) → O2(g) + 2H2O(l) + 4e− Each equation can be used once, more than once or not at all. Give the letter of an equation which (a) shows the formation of gas that forms a white precipitate with limewater, ………………………………………………………………………………..… [1] (b) shows a reaction that forms a blue precipitate, ………………………………………………………………………………..… [1] (c) shows only oxidation, ………………………………………………………………………………..… [1] (d) shows the neutralisation of hydrochloric acid by sodium hydroxide, ………………………………………………………………………………..… [1] (e) shows the reaction at an inert positive electrode when copper(II) sulfate is electrolysed. ………………………………………………………………………………..… [1] [Total: 5]

EDG/PRELIM22/CHEM/6092/02/4EXP/BN [Turn over 3 A2 Seawater contains a variety of dissolved salts. (a) The diagram shows a simple distillation apparatus that can be used to produce purified water from seawater. Explain how distillation purifies seawater. ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………….… [3] (b) Magnesium chloride, MgC l 2, is present in seawater at a concentration of 1.26 g/dm3. (i) Write the formulae for the ions present in magnesium chloride. ………………………………………………………………………..... [1] (ii) Calculate the concentration of chloride ions, in mol /dm3, arising from the magnesium chloride in seawater. [1]

EDG/PRELIM22/CHEM/6092/02/4EXP/BN 4 (iii) Aqueous silver nitrate is added to a small sample of seawater. Describe what you would observe. ………………………………………………………………………..... [1] (c) The concentration of sulfate ions in seawater is 1.24 g/dm3. Excess aqueous barium chloride is added to a 50.0 cm 3 sample of seawater. (i) Write the ionic equation for the precipitation reaction ………………………………………………………………………..... [1] (ii) Hence, calculate the mass of barium sulfate precipitated. [3] [Total: 10]

EDG/PRELIM22/CHEM/6092/02/4EXP/BN [Turn over 5 A3 Silicon is an element in Group IV of the Periodic Table. (a) Give the electronic configuration for a silicon atom. ……………………………………………………………………………….… [1] (b) Silicon reacts with chlorine on heating to form silicon(IV) chloride, SiCl4. Construct an equation for this reaction. ……………………………………………………………………………….… [1] (c) Silicon(IV) chloride is a simple molecular compound. (i) Suggest two physical properties of silicon( IV) chloride other than solubility. 1 ………………………………………………………………………...... 2 ……………………………………………………………………..... [2] (ii) Draw a ‘dot-and-cross’ diagram to show the bonding in silicon( IV) chloride. Show the outer electrons only. [2] [Total: 6]

EDG/PRELIM22/CHEM/6092/02/4EXP/BN 6 A4 Analysis of compound Y shows it has the following composition. element percentage by mass hydrogen 3.4 nitrogen 12.0 oxygen 41.0 vanadium 43.6 (a) Determine the empirical formula of Y. [3] (b) Suggest one property of aqueous Y caused by the presence of vanadium. ……………………………………………………………………………….… [1] (c) Aqueous sodium hydroxide is added to solid Y and the mixture is warmed. A colourless gas that turns moist red litmus blue is evolved. Deduce the formula of each of the two ions present in Y. ……………………………………………………………………………………... ……………………………………………………………………………….… [2]

EDG/PRELIM22/CHEM/6092/02/4EXP/BN [Turn over 7 (d) An acidified aqueous solution of Y reacts with aqueous potassium iodide to form iodine. State and explain what you can deduce about the redox nature of Y. ……………………………………………………………………………………... ……………………………………………………………………………….… [2] (e) When solid Y is heated, only V2O5, water and gas Z are formed. (i) Name gas Z. ………………………………………………………………………..... [1] (ii) Write an equation for the reaction. ………………………………………………………………………..... [1] [Total: 10] A5 Sodium can react with compounds called crown ethers. A typical crown ether is shown below. (a) Write the empirical formula for this crown ether. ……………………………………………………………………………….… [1]

EDG/PRELIM22/CHEM/6092/02/4EXP/BN 8 (b) When sodium reacts with crown ethers it forms Na + and Na– ions. Draw the structure of an Na– ion. Show all the electrons. [1] (c) Sodium reacts violently with chlorine gas to form sodium chloride. Write an equation for the reaction of sodium with chlorine. ……………………………………………………………………………….… [1] (d) The melting point of sodium chloride is 801 °C. The melting point of chlorine is –101 °C. Explain, in terms of structure and bonding, the difference between the melting points of these two substances. ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………….… [4]

EDG/PRELIM22/CHEM/6092/02/4EXP/BN [Turn over 9 (e) Sodium chloride can be broken down into its elements by electrolysis. Explain why pure sodium chloride can be electrolysed at 1000 °C but not at 600 °C. ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………….… [2] [Total: 9] A6 Ethanoic acid is manufactured in the factories by a reaction between methanol, CH 3OH, and carbon monoxide. CH3OH + CO → CH3COOH ΔH = –137 kJ/mol (a) Complete the energy profile diagram for the reaction between methanol and carbon monoxide. On your diagram label • the reactants and products, • the enthalpy change for the reaction, • the activation energy. [3]

EDG/PRELIM22/CHEM/6092/02/4EXP/BN 10 (b) As a safety measure, c arbon monoxide detectors are fitted in the factories. The orange spot turns black if there is a high concentration of carbon monoxide in the air. (i) Why is carbon monoxide hazardous? …………………………………………………………………………….. ………………………………………………………………………..... [1] (ii)