Copy of CHIJ 2024 Sec 4E Chemistry Prelim P3

CHIJSec/2024/OLevelPrelim/6092/03 CONVENT OF THE HOLY INFANT JESUS SECONDARY Preliminary Examination in preparation for the General Certificate of Education Ordinary Level 2024 CANDIDATE NAME CLASS REGISTER NUMBER CHEMISTRY Paper 3 Practical Candidates answer on the question Paper. Additional Materials: As listed in the confidential instructions 6092/03 15 August 2024 1 hour 50 minutes READ THESE INSTRUCTIONS FIRST Write your class, register number and name in the spaces on top of this page. Write in dark blue or black pen on both sides of the paper. You may use an HB pencil for any diagrams or graphs. Do not use paper clips, glue or correction fluid. Answer all questions in the spaces provided. The use of an approved scientific calculator is expected, where appropriate. You should show the essential steps in any calculations and record experimental results. Qualitative analysis notes are printed on page 10. 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. Shift Laboratory For Examiner’s Use 1 2 3 Total This document consists of 10 printed pages and 2 blank pages. O

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3 [Turn over CHIJSec/2024/OLevelPrelim/6092/03 1 Hydrated potassium carbonate forms crystals of formula K2CO3•xH2O. You are going to determine the value of x in the formula K 2CO3•xH2O by titration with dilute hydrochloric acid. K2CO3•xH2O + 2HCl → 2KCl + (x+1)H2O + CO2 Read all the instructions below carefully before starting the experiment in Question 1. Instructions P is a solution containing 8.00 g of K2CO3•xH2O in 1.00 dm3 of solution. Q is 0.100 mol/dm3 hydrochloric acid. (a) (i) Put Q into the burette. Pipette 25.0 cm3 of P into a conical flask. Add a few drops of methyl orange indicator to the solution in the conical flask. Add Q from the burette, swirling the flask constantly, until the end-point is reached. Record your titration results in the space provided. Repeat the titration as many times as you consider necessary to achieve consistent results. Results [5] (ii) From your titration results, obtain an average volume of Q used. Show clearly how you obtained this volume. average volume of Q ………………………. cm3 [1]

4 CHIJSec/2024/OLevelPrelim/6092/03 (b) Q is 0.100 mol/dm3 hydrochloric acid. Using your results from (a), calculate the amount, in mol, of potassium carbonate in 25.0 cm3 of P. amount of potassium carbonate in 25.0 cm3 of P ………………………. mol [2] (c) Using your answer from (b), calculate the amount , in mol, of potassium carbonate in 1.00 dm3 of P. amount of potassium carbonate in 1.00 dm3 of P ………………………. mol [1] (d) (i) Using your answer from (c), calculate the concentration, in g /dm3, of potassium carbonate in P. [Mr: K2CO3, 138] concentration of potassium carbonate ………………………. g/dm3 [1] (ii) Hence, calculate the mass of water in 8.00 g of hydrated potassium carbonate. mass of water ………………………. g [1]

5 [Turn over CHIJSec/2024/OLevelPrelim/6092/03 (iii) Hence, calculate the amount , in mol, of water in 8.00 g of hydrated potassium carbonate. [Mr: H2O, 18] amount of water = ………………………. mol [1] (iv) Calculate the value of x in the formula K2CO3•xH2O. x = ………………………. [1] (e) Describe another method by which the value of x in the formula K 2CO3•xH2O can be determined. Your method should include the apparatus you would use , and the measurements you would take in order to carry out the calculations required. You may use the space below to present your answers. You can assume the apparatus and reagents normally found in a school laboratory are available. [Mr: K2CO3, 138; Mr: H2O, 18] ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... …………………………………………………………………………………………………….. ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... …………………………………………………………………………………………………….. ……………………………………………………………………………………………………... …………………………………………………………………………………………………. [5] [Total: 18]

6 CHIJSec/2024/OLevelPrelim/6092/03 2 E924 is a compound commonly used as a flour improver to strengthen dough in baking. E924 contains the elements potassium, bromine and oxygen. You are provided with a solid sample of E924, labelled X. Read all the instructions below carefully before starting the experiment in Question 2. Instructions (a) Adjust the Bunsen burner to give a non -luminous flame. Moisten the end of a wooden splint with deionised water, and dip the moist end of the splint into the sample of solid X. Place this end of the splint in the Bunsen burner flame. Record your observation. …………………………………………………………………………………………………….. …………………………………………………………………………………………………. [1] (b) Heat sample X in the test-tube gently for about 2 minutes. Record all your observations, including testing the gas produced with a glowing splint. ……………………………………………………………………………………………………... ……………………………………………………………………………………………………... …………………………………………………………………………………………………….. …………………………………………………………………………………………………. [2]

7 [Turn over CHIJSec/2024/OLevelPrelim/6092/03 (c) The residue from (b) is dissolved in deionised water. This resulting solution is solution Y. Carry out the following tests on solution Y. Record your observations in the table. test observations Test 1 Place about 2 cm depth of solution Y into a clean test-tube. Add, with shaking, an equal volume of potassium iodide solution. Then add a few drops of starch solution and shake the test-tube. Test 2 Place about 2 cm depth of solution Y into a clean test-tube. Add an equal portion of dilute nitric acid. Then add a few drops of aqueous silver nitrate. Test 3 Place about 1 cm depth of solution Y into a clean test-tube. Add aqueous sodium hydroxide slowly with shaking until no further change is seen. [4] (d) State whether solution Y is an oxidising or reducing agent, explain your reasoning. nature of solution Y …………………………………………………………………………… reasoning ……………………………………………………………………………………….. …………………………………………………………………………………………………….. …………………………………………………………………………………………………. [2] [Total: 9]

8 CHIJSec/2024/OLevelPrelim/6092/03 3 You will determine the enthalpy change for a metal displacement reaction using a known volume and concentration of aqueous copper(II) sulfate and excess zinc powder. The equation for this reaction is shown. Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s) Read all the instructions below carefully before starting the experiment. Instructions S is approximately 3 g of zinc powder. T is 0.800 mol/dm3 copper(II) sulfate. (a) Place a Styrofoam cup into a beaker. Use a measuring cylinder to measure 25 cm3 of T into the Styrofoam cup. Measure the initial temperature of T at time = 0 minute and record the value in the table. Start the stopwatch, and do not stop the stopwatch until the whole experiment has been completed. Record the temperature of T at time = 0.5 minutes and time = 1 minute, and record the values in the table. At time = 1 .5 minutes, carefully add the zinc powder to the Styrofoam cup. Using the thermometer, continually stir the mixture. Record the temperature every half a minute in the table until time = 5 minutes. Stir the mixture between thermometer readings. time / min temperature / °C 0 0.5 1 1.5 – 2 – 2.5 3 3.5 4 4.5 5 5.5 [3]

9 [Turn over CHIJSec/2024/OLevelPrelim/6092/03 (b) Plot a graph of temperature against time on the grid belo