Cambridge A Level Chemistry 9701 — 2002 Oct/Nov Paper 3 · Variant 1

This question paper consists of 7 printed pages and 1 blank page. SP (SM) S25940/2 © CIE 2002 [Turn over CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level CHEMISTRY 9701/3 PAPER 3 Practical Test OCTOBER/NOVEMBER SESSION 2002 1 hour 15 minutes Candidates answer on the question paper. Additional materials: As listed in Instructions to Supervisors Electronic calculator and/or Mathematical tables TIME 1 hour 15 minutes INSTRUCTIONS TO CANDIDATES Write your name, Centre number and candidate number in the spaces at the top of this page. Answer all questions. Write your answers in the spaces provided on the question paper. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. You may use a calculator. You are advised to show all working in calculations. Use of a Data Booklet is unnecessary. Qualitative analysis notes are printed on pages 6 and 7. FOR EXAMINER’S USE 1 2 TOTAL Candidate Centre Number Number Candidate Name

2 9701/3/O/N/02 1 FA 1 is a hydrated metal sulphate, XSO4.7H2O. You are required to determine the mass of water of crystallisation (the 7H2O in the formula above) in a weighed sample of FA 1 and to calculate the relative atomic mass, Ar, of the element X. (a) Accurately weigh the hard glass test-tube provided. Record the mass in Table 1.1 below. Add to the test-tube between 2.00 g and 2.50 g of FA 1 and accurately weigh the test- tube and contents. Record this mass in Table 1.1 below. Table 1.1 Mass of FA 1 (b) Heat the test-tube, gently at first then strongly, to drive off the water of crystallisation. The crystals will ‘crackle’ at first as water is lost and ‘steam’ (condensed water vapour) will be seen coming out of the mouth of the tube. If the crystals are overheated the sulphate can decompose and give off sulphur trioxide which will be seen as white fumes. If you see white fumes, do not confuse this with steam, stop heating. Place the test-tube on a heat proof mat and leave to cool. Do not move about the laboratory with a hot test-tube. (You are advised to continue with the second question while the tube cools.) When cool, reweigh the test-tube and its contents. Record the mass in Table 1.2 below. Table 1.2 Mass of FA 1 after heating (c) By repeating the heating, cooling and reweighing, show clearly by your results in Table 1.2 that all the water of crystallisation has been driven from the crystals, FA 1. [4] Accuracy [6] For Examiner’s Use Mass of test-tube + FA 1 / g Mass of empty test-tube / g Mass of FA 1 / g Mass of test-tube + FA 1 after heating / g Mass of empty test-tube (from Table 1.1) / g Mass of FA 1 after heating / g

3 9701/3/O/N/02 [Turn over (d) Calculate (i) the mass of anhydrous XSO4 present in the crystals. (ii) the mass of water driven from the crystals of FA 1. [1] (e) Calculate how many moles of water are present in the sample of FA 1 used. [Ar; H, 1.0; O, 16.0.] [1] (f) Use your answer to (e) and the formula XSO4.7H2O to calculate how many moles of XSO4 are present in the sample of FA 1 used. [1] (g) Use your answers to (d) and (f) to calculate the relative molecular mass, Mr, of XSO4. [1] (h) Calculate the relative atomic mass, Ar, of the element X. [Ar; O, 16.0; S, 32.0.] [1] [Total : 15] For Examiner’s Use

4 9701/3/O/N/02 2 The solution FA 2 contains two cations and two anions from the following list: (Al 3+, NH4 +, Ba2+, Ca2+, Cr3+, Cu2+, Fe2+, Fe3+, Pb2+, Mg2+, Mn2+, Zn2+; CO3 2–, CrO4 2–, Cl –, Br–, I–, NO3 –, NO2 –, SO4 2–, SO3 2–). In all tests, the reagent should be added gradually until no further change is observed, with shaking after each addition. Record your observations and the deductions you make from them in the spaces provided. Your answers should include • details of colour changes and precipitates formed, • the names of gases evolved and details of the test used to identify each one. You should indicate clearly at what stage in a test a change occurs, writing any deductions you make alongside the observations on which they are based. Marks are not given for chemical equations. No additional or confirmatory tests for ions present should be attempted. Candidates are reminded that definite deductions may be made from tests where there appears to be no reaction. For Examiner’s Use Test Observations [5] Deductions [4] (a) Place 3 cm depth of FA 2 in a boiling-tube, add an equal depth of dilute aqueous sodium hydroxide. Cautiously warm the tube. (b) Filter the mixture from (a) and collect the filtrate. Leave the residue in the filter paper and observe it again after several minutes. (c) Place 2 cm depth of the filtrate from (b) in a test- tube and add dilute nitric acid, drop by drop, until no further change is seen.

5 9701/3/O/N/02 [Turn over Summary The cations present in FA 2 are …………… and …………… The anions in FA 2 are …………… and …………… [1] [Total : 10] For Examiner’s Use Test Observations Deductions (d) Place 2 cm depth of the filtrate from (b) in a boiling-tube. Add a piece of aluminium foil. Cautiously warm the tube. (e) Place 3 cm depth of FA 2 in a test-tube, add an equal depth of dilute aqueous ammonia. Cautiously warm the tube. Filter the mixture. Add dilute nitric acid, drop by drop, to the filtrate until no further change is seen. (f) Place 2 cm depth of FA 2 in a test-tube, add dilute hydrochloric acid, followed by aqueous barium chloride. (g) Place 2 cm depth of FA 2 in a test-tube, add dilute nitric acid, followed by aqueous silver nitrate.

6 9701/3/O/N/02 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.] 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

7 9701/3/O/N/02 2 Reactions of anions 3 Tests for gases 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

CAMBRIDGE INTERNATIONAL EXAMINATIONS NOVEMBER 2002 GCE Advanced Subsidiary Level UNIVERSITY of CAMBRIDGE Local Examinations Syndicate

Page 1 Mark Scheme | Syllabus | Paper AS Level Examinations — November 2002 9701 3 N.B. Boxed references within this marking scheme relate to the accompanying booklet of Standing Instructions Tables 1.1 and 1.2 Give one mark if all weighings are to 2 decimal places or better. Give one mark if the mass of FA 1 recorded in Table 1.1 is between 2.00g and 2.50g inclusive. Give one mark if there is evidence of reheating and reweighing the tube. Give one mark if two masses of tube + FA 1 after heating are within 0.05 g. Withhold one of these marks if there is an error in subtraction the mass of empty tube differs between the two tables the smallest mass of tube + FA 1 after heating was not used in calculating the residual mass of FA 1. Accuracy Supervisor’s Script Check and correct any errors in subtraction mass lost on heating Calculate mass of FA 1 after heating correct to 2 decimal places. Record this as a ringed total on the front of the Supervisor's script. The value of this ratio = 1.05 If there is a significant difference in the value obtained for the Supervisor it may suggest an impure sample of MgSO,.7H20 has been used or the wrong salt distributed. Candidate Scripts Check and correct any errors in subtraction mass lost on heating Calculate mass of FA tafter heating correct to 2 decimal places. Record this ratio, correct to 2 decimal places, below Table 1.2. Compare the ratio obtained from the candidate’s results (corrected where necessary) with the theoretical value of 1.05. Accuracy marks are awarded for differences between the ratios as follows: Mark Difference in Ratio 6 Up to 0.03 5 0.03+ to 0.04 4 0.04+ to 0.05 3 0.05+ to 0.07 2 0.07+ to 0.10 41 0.10+ to 0.15 0 Greater than 0.15

Page 2 Mark Scheme Syllabus | Paper AS Level Examinations — November 2002 9701 3 (a) (e) (f (g) (h) Ignore Give one mark for Give one mark for (i) Calculated mass of anhydrous magnesium sulphate and (ii) Correctly calculated mass of water mass of water moles of water’ = 18 (If an incorrect M, is used this mark is not awarded but subsequent marks may be given) Give one mark for Give one mark for Give one mark for moles of XSO, = Answer tole) Answer to (d)(i) so, = Answer to(d)(i) M, of XSO, Answer to (f) answer to(g) - 96 No Units No Units (Do not penalise twice) Total for Question 1 15

FA 3 contains the cations and the anions Mn2* Page 3 Mark Scheme Syllabus | Paper AS Level Examinations — November 2002 9701 3. FA 2is a solution containing Mn", Zn**, SO,?, NOs" Test Observations Deductions To 3 cm depth of FA 2 in a boiling- Off-white, buff or light brown {a) tube, add an equal depth of dilute precipitate. aqueous sodium hydroxide. (Not dirty brown, brown or any yellow | Manganese or Mn®* (1 or red in the colour) {1} Cautiously warm the tube. No ammonia, no alkaline gas, no gas | No ammonium salt, no NH," turning litmus or UI paper blue… [1] for observation and deduction T i—| (b) Filter the mixture from (a) and Allow precipitate colour here if not collect the filtrate. given in (a). Deduction in (a) can be given from observation here. Leave the residue in the filter paper Manganese or Mn** and observe again after several Precipitate turns brown or darkens: (one mark if not already given in (a)) minutes. (No red or yellow in colour) 1) {c) Place 2 cm depth of the filtrate from | White precipitate forms and Pb**, Al** or Zn?" (any one) (b) in a test-tube and add dilute re-dissolves .. weseee nitric acid, drop by drop, until no [1] for observation and deduction further change is seen. (d) Place the remainder of the filtrate from (b) in a boiling-tube. Add a Gas turns red litmus blue or gives piece of aluminium foil. white smoke with HCI or Nitrate or nitrite Cautiously warm the tube. Ammonia gas 1] NOs’ or NOZ 1) (e) To 3 cm depth of FA 2 in a test- The observation marks from (a) or (b) | Manganese or Mn** tube, add an equal depth of dilute can be given here. (one mark if not already given in (a) aqueous ammonia. or (b)) Filter the mixture and add dilute White precipitate forms and Zn** [4] for observation and nitric acid, drop by drop, until no re-dissolves... deduction further change is seen. Take care that deduction mark is not given for a ppt formed on adding ‘| ammonia (fy To 2 cm depth of FA 2 ina test- No brown gas… No nitrite [1] for observation and tube, add dilute hydrochloric acid deduction followed by aqueous barium chloride. White precipitate. Sulphate [1] for observation and deduction —________—_} (g) To2cm depth of FA 2in a test- No brown gas .. No nitrite [1] for observation and tube, add dilute nitric acid deduction if not already given in () followed by aqueous silver nitrate. No precipitate, no reaction, no change ... 7 No halide or No chloride, bromide, iodide (any one) [1] for observation and deduction | 4 Summary (Only award these marks if there is supporting evidence in the individual tests) and Zn** so,? and NO, Total of 12 scoring points If the mark is in excess of 10 cross through the mark and record 10 max. Total for Question 2 is 10 and for the Paper 25.