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CIE Nov 2013 v3 Paper 3 Q2
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![Examiners For Use In this experiment you are to determine the formula of hydrated barium chloride, FA 5, by heating to remove the water of crystallisation. You will heat two separate samples. The anhydrous barium chloride does not decompose when heated. FA 5 is hydrated barium chloride, BaCl 2.xH2O (a) Method Record all weighings, in an appropriate form, in the space below.Record the mass of the empty crucible without its lid. Add between 2.0 and 2.4 g of FA 5 into the crucible. Record the mass of the crucible and its contents. Use a pipe-clay triangle to support the crucible and contents on a tripod. Heat the crucible and its contents gently for about one minute with the lid off. Then heat strongly for a further four minutes. Put the lid on the crucible and leave to cool for approximately 10 minutes. While you are waiting for the crucible to cool, start work on Question 3.When the crucible is cool, remove the lid, and weigh the crucible with the residue. Record the mass of anhydrous barium chloride remaining in the crucible after heating and the mass of water lost. To prepare for the second experiment, use a spatula to remove the residue from the crucible into the beaker labelled waste. Reweigh the empty crucible without its lid. Carry out the experiment again. This time use between 1.5 and 1.9 g of FA 5. II III IV VI [6]UCLES 2013 9701/33/O/N/13<br />
Examiners For Use (b) Calculation Show your working in each step. (i) Calculate the mean number of moles of water removed from the hydrated salt in the experiments. (Ar : H, 1.0; O, 16.0) (ii) Calculate the mean number of moles of anhydrous barium chloride produced in the experiments. (Ar : Ba, 137; Cl, 35.5) moles of H2O =mol (iii) Calculate the value of x in the formula of hydrated barium chloride, BaCl 2.xH2O. moles of BaCl 2 =mol x =[3] (c) (i) Suggest how the experimental procedure could be modi ed to ensure that all of the water of crystallisation had been removed by heating hydrated FA 5.(ii) Do you think that the results from your two experiments are consistent with each other? Justify your answer by carrying out appropriate calculations.UCLES 2013 9701/33/O/N/13 [3] [Total: 12] [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/November_2013_v3_QP_-_Paper_3_CIE_Chemistry_A-level_2-0.jpg)
![PMT Page 4 Mark Scheme Syllabus Paper GCE A LEVELOctober/November 2013 9701 33 Question Sections Indicative material Mark Total (v) PDO V All answers are quoted to 3 or 4 significant (cont) Display figures. A minimum of three answers is needed to qualify. (d) (i) ACE % error for pipette = /25100 = 0.24% (or 0.06 Interpretation 0.240%) (ii) ACE + (iii) Interpretation If balance displays to 1 decimal place: error in balance reading is 0.05 g or 0.1(0) g. If balance displays to 2 decimal places: error in balance reading is 0.005 g or 0.01 g. If balance displays to 3 decimal places: error in balance reading is 0.0005 g or 0.001 g. % error = 2 balance error (above) /mass of FA 1 used100 Correct answer is not required, but if the100 [5] factor was omitted, a correctly calculated % error [2] answer scores the mark. [Total: 15] (a) MMO Collection The masses of FA 5 used by the candidate were between 2.02.4 g (expt 1) and 1.51.9 g (expt 2). PDO II Suitable headings for a table or list, shown Display completely for at least one experiment carried out. If 2 experiments, all headings must be correct. (mass of) empty crucible (mass of) crucible + FA 5 (mass of) crucible + residue / FA 5 after heating (mass of) residue (owtte) mass lost or (mass of) water lost. and unit was given covering every weighing; Unit: /g or (g) or in grams or g following each weighing PDO III Records all weighings consistently to at least Recording 1 dp. A minimum of three weighings are needed. Accuracy (Q) marks for gravimetric experiment3 marks available Examiner checks working for mass of residue and mass of water and expresses the mass of hydrated solid ratio /mass of water to 2 dp for each experiment. The expected ratio = /36 = 6.78. 244Cambridge International Examinations 2013<br />
(ii) ACE Correct expression for the number of moles of Interpretation residue with correct masses of anhydrous salt and 208 and answer expressed to 24 sf or correct answer and 24 sf If only one expt carried out then correct calculation for number of moles of residue expressed to 24 sig fig. (iii) ACE Correct calculation of (i)(ii) to give answer as an Interpretation integer. (should be x = 2) (c) (i) ACE Heat to constant mass (owtte) Improvements [3] Page 5 Mark Scheme Syllabus Paper GCE A LEVELOctober/November 2013 9701 33 Question Sections Indicative material Mark Total PMT (a) MMO Award IV if the ratio in expt 1 is between 6.30 and (cont) Quality 7.25. Award V If the ratio in expt 2 is between 6.30 and 7.25. Award VI If the ratio in both of experiments 1 and 2 is between 5.90 and 7.65, inclusive. [6] (b) (i) MMO Correct expression for the number of moles of water Display lost (from mass as recorded) or correct answer. (ii) ACE An attempt to scale mass loss to the mass of FA 5 Interpretation used or to calculate x separately for the two experiments. ACE Uses calculated values to comment sensibly on the Conclusion consistency the results. [3] [Total: 12] FA 6 is (NH4)2Fe(SO4)2(s); FA 7 is Na2CO3(aq); FA 8 is Pb(NO3)2(aq); FA 9 is K2CrO4(aq) (a) (i) MMO Green precipitate and ppt insoluble in excess Collection NaOH/ppt turning brown (in air / on standing). MMO (When heated with NaOH) gas / NH3 turns red litmus Decision to blue. MMO (With BaCl 2), white precipitate forms and insoluble in Collection HCl. (ii) ACE FA 6 contains ammonium ions and sulfate ions. Conclusion (correct evidence needed for each ion in the observations table). (iii) ACE 2+ Fe + 2OH Fe(OH)2 conclusionCambridge International Examinations 2013<br />](https://learnah.org/wp-content/uploads/2018/08/November_2013_v3_MS_-_Paper_3_CIE_Chemistry_A-level_2-0.jpg)
