SJI 2021 Y4 Prelim Chemistry 6092 P2

ST JOSEPH’S INSTITUTION PRELIMINARY EXAMINATION 2021 (YEAR 4) CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Candidates answer on the Question Paper. No Additional Materials are required. 6092/02 20 August 2021 1 hour 45 minutes (11:15 – 13:00) 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 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. Candidates are reminded that all quantitative answers should include appropriate units. Candidates are advised to show all their working in a clear and orderly manner. 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 of this question paper. For Examiner’s Use Section A / 50 B7 / 12 B8 / 8 B9 / 10 Total / 80 This document consists of 22 printed pages including this cover page.

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3 Section A Answer all questions in this section in the spaces provided. The total mark for this section is 50. A1 The chromatogram below shows the results of a paper chromatography experiment. (a) Draw a line, labelled S, on the chromatogram to show the solvent level at the beginning of the experiment. [1] (b) In this experiment, a locating agent i s used on the chromatogram. What is the purpose of a locating agent? ........................................................................................................................[1] (c) Use the chromatogram to answer the following questions. (i) Which substances are impure? ……………………………………...........................................................[1] (ii) Which substances are pure? ………………........................................................................................[1] solvent front start line

4 (d) With the aid of a ruler and indicating the measurements on the chromatogram clearly, calculate the Rf value of the most soluble spot in X. Rf value = .................................................. [2] [Total: 6] A2 This question is about ammonia. (a) Ammonia is manufactured indu strially using the Haber Process and is an important precursor used in the manufacture of ammonium-based fertilisers. (i) State the reaction conditions for the Haber Process. .…………………...………..……………………………………………...…[1] (ii) Explain why it is not advi sable to add ammonium -based fertilisers to soil which has been limed with calcium hydroxide. …….…..……………………………...………………………………………… ………………………..……….…………...…………………………………… ………………………………………………..…………………………...…[2] (b) Aqueous ammonia is commonly used to i dentify cations which are present in salt solutions. (i) Describe how aqueous ammonia can be used to identify iron(II) ions. …………………………………………………..…….………………...……… ………………………………………………………………..…………...…[1] (ii) Write an ionic equation with state symbol s to represent the reaction in (b)(i). [2]

5 (c) Aqueous ammonia reacts with dilute hydrochloric acid to form aqueous ammonium chloride. (i) Explain why evaporation to dryness is not suitable to obtain solid ammonium chloride salt from its salt solution. ……………………….……..………………………………………...………… ……………………………………………………………………..……...…[1] (ii) Hence, suggest a suitable method used to obtain solid ammonium chloride salt. ……………………………………………………………………………..…[1] (d) What is a suitable drying agent that can be used to dry a sample of ammonia gas? ………………………………………..…………..………………………………….[1] [Total : 9] A3 Ethanoic acid is a weak acid and hydrochloric acid is a strong acid. (a) (i) Define the term ‘acid’. …………………………..…………………………..…………………………. …………………………………………………………………………….…[1] (ii) The equation below shows the changes which occur when hydrochloric acid is dissolved in water. HCl(aq) → H+(aq) + Cl-(aq) Write the equation with state symbols to show the changes which occur when ethanoic acid (CH3COOH) is dissolved in water. [2]

6 (b) Jared conducted two experiments as shown below. Experiment 1: He added a portion of copper(II) carbonate to excess dilute hydrochloric acid in a test tube. Experiment 2: He added a portion of copper(II) oxide to excess dilute hydrochloric acid in a test tube. State one similarity and one difference in observations for both experiments. ………………………………………………………………… …….………………… …………………………………………………………………… .…………………… …………………………………………………………………… .…………………… ………………………………………………………………….……………………[2] (c) The salt formed in (b) is aqueous copper(II) chloride. Aqueous potassium iodide reacts with aqueous copper( II) chloride to produce iodine. (i) Balance the chemical equation for this reaction. ……. KI + ……. CuCl2 → ……. CuI + ……. I2 + ……. KCl [1] (ii) Is the reaction in (c)(i) a redox reaction? Explain your answer in terms of oxidation numbers. ……………………………………………………………………………..…… ………………………………………………………………………..………… …………………………………………………………………… .…………[2]

7 (d) Complete the method of preparing pure dry crystals of zinc chloride from dilute hydrochloric acid and a base. step 1: Add …..………………………………………………. to dilute hydrochloric acid. step 2: …………………...…………………………………………………………………….. step 3: Heat the …………………….……….. to ……………………………………, leave the solution to cool. Collect the crystals by filtration. step 4: …………………………………………..…………………..…………………………. .……………………………………………………………………….……………...[4] [Total: 12]

8 A4 Two experiments are carried out to investigate the rate of reaction between excess powdered zinc carbonate and dilute hydrochloric acid. The results are shown in the graph below. In Experiment 1, 30.0 cm3 of 0.500 mol dm-3 hydrochloric acid is used. (a) Below shows the suggestions by two students to modify Experiment 1 to obtain the graph for Experiment 2. Student A: The concentration of the hydrochloric acid should be decreased. Student B: Use granulated zinc carbonate granules. Comment on the suggestions made by the students. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ........................................................................................................................[2] (b) (i) Besides the factors in (a), suggest one other factor that can be changed to produce the graph in Experiment 2. ..…………………………..………………….…………………………...…[1] 0 volume of carbon dioxide / cm3 time / min Experiment 1 Experiment 2

9 (ii) Expl