Cambridge A Level Chemistry 9701 — 2004 May/June Paper 3 · Variant 1

This document consists of 7 printed pages and 1 blank page. MML 5664 4/03 S65492/2 © UCLES 2004 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level CHEMISTRY 9701/03 Paper 3 Practical Test May/June 2004 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Instructions to Supervisors. READ THESE INSTRUCTIONS FIRST Write your details, including examination session and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen in the spaces provided on the Question Paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. 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. You are advised to show all working in calculations. Use of a Data Booklet is unnecessary. Qualitative Analysis notes are provided on pages 6 and 7. Centre Number Candidate Number Name For Examiner’s Use LABORATORY SESSION 1 2 TOTAL If you have been given a label, look at the details. If any details are incorrect or missing, please fill in your correct details in the space given at the top of this page. Stick your personal label here, if provided.

© UCLES 2004 2 9701/03/M/J/04 For Examiner's Use 1 FA 1 is anhydrous sodium carbonate, Na2CO3, provided in a stoppered tube. FA 2 is an aqueous solution of hydrochloric acid, HCl. Acids and carbonates in solution react as shown in the equation. 2H+(aq) + CO3 2–(aq) →H2O(l) + CO2(g) You are to determine the concentration, in mol dm–3, of the hydrochloric acid solution FA 2. (a) Weigh the stoppered tube labelled FA 1 and record the mass in Table 1.1. Table 1.1 Weighing of sodium carbonate [1] Transfer the contents of the weighed tube into a 250 cm3 beaker and dissolve the solid in about 100 cm3 of distilled water. Reweigh the tube and stopper and any residual sodium carbonate and record the mass in Table 1.1. Calculate the mass of sodium carbonate dissolved in the water. (b) Transfer the sodium carbonate solution to the graduated flask labelled FA 3. Rinse the beaker with distilled water several times, adding each rinsing to the graduated flask. This ensures that all of the sodium carbonate has been transferred to the flask. Make up the solution to 250 cm3 with distilled water and mix thoroughly. Pipette 25.0 cm3 of FA 3, the sodium carbonate, into a conical flask and place the flask on a white tile. Add a few drops of the indicator provided and titrate with FA 2, the hydrochloric acid. Repeat the titration as many times as you think necessary to obtain accurate results. Make certain that the recorded results show the precision of your practical work. Table 1.2 Titration of FA 3 with FA 2 Indicator used: … [2] + [6] Summary 25.0 cm3 of FA 3 reacted with … cm3 of FA 2. Show which results you used to obtain this volume of FA 2 by placing a tick () under the readings in Table 1.2. Mass of tube + FA 1 / g Final burette reading / cm3 Initial burette reading / cm3 Volume of FA 2 used / cm3 Mass of tube + residual FA 1 / g Mass of FA 1 used / g

You are advised to show full working in all parts of the calculations. (c) Calculate the concentration in mol dm–3 of the sodium carbonate, Na2CO3, in FA 3. [Ar: Na, 23.0; C, 12.0; O, 16.0.] [2] (d) Calculate how many moles of sodium carbonate, Na2CO3, were pipetted into the conical flask. [1] (e) Calculate how many moles of hydrochloric acid, HCl, have been run from the burette. 2H+(aq) + CO3 2–(aq) →H2O(l) + CO2(g) [1] (f) Calculate the concentration, in mol dm–3, of HCl in FA 2. [2] [Total: 15] 3 9701/03/M/J/04 [Turn over For Examiner's Use © UCLES 2004

2 FA 4, which is provided in a stoppered boiling-tube, is a mixture of two solids: FA 5, which is soluble in water and FA 6, which is insoluble in water. Add 20 cm3 of distilled water to the boiling-tube and carefully warm the mixture to dissolve FA 5. Filter the mixture and retain both the filtrate and the residue. Carry out the following tests and identify any gases given off. Tests on the Filtrate (FA 5) Use the information in the Qualitative Analysis Table on page 7 to identify the anion present in FA 5. The anion present in FA 5 is … Which observations support your choice of this anion? … … … [1] 4 9701/03/M/J/04 For Examiner's Use © UCLES 2004 Test Observations [4] (a) To 1 cm depth of the filtrate in a test-tube, add 1 cm depth of aqueous barium chloride; followed by 2 cm depth of dilute hydrochloric acid. (b) To 1 cm depth of the filtrate in a test-tube, add 1 cm depth of acidified aqueous potassium dichromate(VI). Leave to stand for 1 minute. (c) To 1 cm depth of the filtrate in a boiling-tube, add 2 cm depth of dilute hydrochloric acid. Warm the solution and identify the gas given off. Empty and wash away the contents of the tube at the end of this test. (d) To 1 cm depth of the filtrate in a test-tube, add 2 cm depth of aqueous iodine.

In tests (b) and (d) the anion in FA 5 is behaving as … [1] Tests on the Residue (FA 6) Use a spatula to transfer the residue from the filter paper to a boiling tube. Use the information in the Qualitative Analysis Table on pages 6 and 7 to identify the cation and anion present in FA 6. The cation present in FA 6 is … The anion present in FA 6 is … Which observations support your choice of these ions? cation … … anion … … [1] [Total: 10] 5 9701/03/M/J/04 [Turn over For Examiner's Use © UCLES 2004 Test Observations [3] (e) Add 2 cm depth of hydrochloric acid to the residue (FA 6) in the boiling-tube. Use the solution formed in this test for the following tests, (f) and (g). (f) To 1 cm depth of the solution made in test (e) in a test-tube add aqueous sodium hydroxide. (g) To 1 cm depth of the solution made in test (e) in a test-tube add 1 cm depth of aqueous ammonia.

QUALITATIVE ANALYSIS NOTES [Key: ppt. = precipitate] 1 Reactions of aqueous cations [Lead(II) ions can be distinguished from aluminium ions by the insolubility of lead(II) chloride.] 6 9701/03/M/J/04 © UCLES 2004 aluminium, Al 3+(aq) ammonium, NH4 +(aq) barium, Ba2+(aq) calcium, Ca2+(aq) chromium(III), Cr3+(aq) zinc, Zn2+(aq) copper(II), Cu2+(aq) iron(II), Fe2+(aq) iron(III), Fe3+(aq) lead(II), Pb2+(aq) magnesium, Mg2+(aq) manganese(II), Mn2+(aq) reaction with NaOH(aq) NH3(aq) white ppt. soluble in excess ammonia produced on heating no ppt. (if reagents are pure) green ppt. insoluble in excess green ppt. insoluble in excess white ppt. with high [Ca2+ (aq)] pale blue ppt. insoluble in excess blue ppt. soluble in excess giving dark blue solution white ppt. soluble in excess white ppt. insoluble in excess white ppt. insoluble in excess white ppt. insoluble in excess white ppt. soluble in excess white ppt. soluble in excess grey-green ppt. soluble in excess giving dark green solution red-brown ppt. insoluble in excess off-white ppt. insoluble in excess off-white ppt. insoluble in excess white ppt. insoluble in excess no ppt. no ppt. grey-green ppt. insoluble in excess red-brown ppt. insoluble in excess ion

© UCLES 2004 2 Reactions of anions 3 Tests for gases 7 9701/03/M/J/04 carbonate, CO3 2– chromate(VI), CrO4 2–(aq) chloride, Cl–(aq) bromide, Br–(aq) iodide, I–(aq) nitrate, NO3 –(aq) nitrite, NO2 –(aq) sulphate, SO4 2–(aq) sulphite, SO3 2–(aq) ion reaction CO2 liberated by dilute acids yellow solution turns orange with H+(aq); gives yellow ppt. with Ba2+(aq); gives bright yellow ppt. with Pb2+(aq) gives white ppt. with Ag+(aq) (soluble in NH3(aq)); gives white ppt. with Pb2+(aq) NH3 liberated on heating with OH–(aq) and Al foil, NO liberated by dilute acids (colourless NO →(pale) brown NO2 in air) gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq)); gives white ppt. with Pb2+(aq) NH3 liberated on heating with OH–(aq) and Al foil SO2 liberated with dilute acids; gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid) gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq)); gives yellow ppt. with Pb2+(aq) gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acid) gas test and test result turns damp red litmus paper blue gives a white ppt. with limewater (ppt. dissolves with excess CO2) bleaches damp litmus paper ‘pops’ with a lighted splint relights a glowing splint turns potassium dichromate(VI) (aq) from orange to green ammonia, NH3 carbon dioxide, CO2 chlorine, Cl 2 hydrogen, H2 oxygen, O2 sulphur dioxide, SO2

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