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CIE Mar 2016 v3 Paper 3 Q2
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![You will determine the concentration of the hydrochloric acid used in Question 1 by titration of a diluted solution of FA 1 with aqueous sodium hydroxide of known concentration. PMT NaOH(aq) + HCl (aq)NaCl (aq) + H2O(l) FA 3 is a diluted solution of FA 1, hydrochloric acid, HCl. FA 3 was prepared by running 25.00 cm3 of FA 1 into a volumetric flask and adding distilled water until the total volume was 250.0 cm3. FA 4 is 0.100 mol dm3 sodium hydroxide, NaOH. bromophenol blue indicator (a) MethodFill the burette with FA 4. Pipette 25.0 cm3 of FA 3 into a conical flask. Add about 10 drops of bromophenol blue. Perform a rough titration and record your burette readings in the space below. The end point is reached when the solution becomes a permanent blue-violet colour. The rough titre iscm3.Carry out as many accurate titrations as you think necessary to obtain consistent results. Make certain any recorded results show the precision of your practical work. Record, in a suitable form below, all of your burette readings and the volume of FA 4 added in each accurate titration. II III IV VI VII [7] (b) From your accurate titration results, obtain a suitable value to be used in your calculations. Show clearly how you obtained this value. 25.0 cm3 of FA 3 requiredcm3 of FA 4. [1]UCLES 2016 9701/33/F/M/16 [Turn over<br />
PMT (c) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (i) Calculate the number of moles of sodium hydroxide present in the volume of FA 4 recorded in (b). (ii) Use your answer to (i) and the equation on page 5 to determine the number of moles of hydrochloric acid present in 25.0 cm3 of FA 3. moles of NaOH =mol (iii) Use your answer to (ii), and any relevant information given on page 5, to calculate the concentration, in mol dm3, of hydrochloric acid in FA 1. moles of HCl =mol (iv) Show, by calculation, that the hydrochloric acid in Question 1 was in excess. concentration of HCl in FA 1 =mol dm3 (d) The error in the volume reading of a pipette is 0.06 cm3 which gives a maximum percentage error of 0.24% for 25.0 cm3 of FA 3. The error in a single burette reading is 0.05 cm3. Calculate the maximum percentage error in the volume of FA 4 used in (b) and deduce which solution, FA 3 or FA 4, was measured more accurately. [5] maximum percentage error for volume of FA 4 in (b) =%was measured more accurately. [1] [Total: 14]UCLES 2016 9701/33/F/M/16<br />](https://learnah.org/wp-content/uploads/2018/08/March_2016_v3_QP_-_Paper_3_CIE_Chemistry_A-level_2-0.jpg)
![Page 3 question Cambridge International AS/A LevelMarch 2016 Mark Scheme Syllabus Paper 9701 33 indicative material mark total (a) I Initial and final burette readings and volume added recorded for rough titre and accurate titre details tabulated. II Initial and final burette readings recorded and volume of FA 4 added recorded for each accurate titration. All headings and units correct for accurate titrations: initial / final (burette) reading / volume or reading / volume at start / finishvolume / FA 4 added / used or titre(cm3) or / cm3 or in cm3 or cm3 by every entry. III All accurate burette readings are recorded to the nearest 0.05 cm3. IV Has two uncorrected, accurate titres within 0.1 cm3. V, VI and VII Award V, VI and VII for0.20 cm3 Award V and VI for 0.20 cm3 <0.30 cm3 Award V for 0.30 cm3 <0.50 cm3 [7] (b) Mean titre correctly calculated from clearly selected values. [1]Candidates must average two (or more) titres where the total spread is0.20 cm3.Working must be shown or ticks must be put next to the two (or more) accurate readings selected.The mean should normally be quoted to 2 d.p. rounded to the nearest 0.01. Note: the candidates mean will sometimes be marked as correct even if it is different from the mean calculated by the examiner for the purpose of assessing accuracy. (c)(i)(ii) Correctly calculates 0.100 (b) 1000 and (ii) = (i) (iii) Correct expression (c)(ii) 1000 10 25 (iv) mol Mg = mass in 1(a) / 24.3 and mol HCl = (c)(iii)25 / 1000 mol HCl > 2mol Mg (owtte) so the statement is correct. Allow ecf from incorrect (iii). Final answers (i), (ii) and (iii) to 3 or 4 sig. fig. and no rounding errors. [5] 1 1 1 1Cambridge International Examinations 2016<br />
Cambridge International AS/A LevelMarch 2016 Mark Scheme Syllabus Paper 9701 33 indicative material (d) Correct expression 0.1 100 (b) and answer to minimum 2 sig. fig. / correct answer to minimum 2 sig.fig. and FA 3 (is measured more accurately). Allow ecf from (b) > 41.67 cm3 then FA 4 (is measured more accurately). mark total [1] Page 4 question NaOH NH3 HCl (warm) H+ / MnO4 Ba2+ / HCl question test observations FA 5 FA 6 no reaction / no change / no ppt white ppt, soluble in excess no reaction / no change / no ppt white ppt, insoluble in excess blue solution brown gas / gas turning brown / gas turns blue litmus red / bleaches no reaction / no change decolourises / purple to colourless or (solution) stays colourless stays purple / pink or changes to purple / pink no reaction / no change / no ppt white ppt, insoluble in HCl indicative material mark total FA 5 is NaNO2; FA 6 is Al2(SO4)3; FA 7 is Na2SO3 (Na2S2O5) (a) Observations fully correct for both FA 5 and FA6 for NaOH. Observations fully correct for both FA 5 and FA6 for NH3. Observation of blue solution or brown gas with FA 5 and no reaction with FA 6 for HCl. Observations fully correct for both FA 5 and FA6 for H+ / MnO4 . Observations fully correct for both FA 5 and FA6 for Ba2+ / HCl. Cations: FA 5 unknown and FA 6 Al Anions: FA 5 NO2 FA 6 SO4 / nitrite / sulfate 3+ / aluminium [8] 1 1 1Cambridge International Examinations 2016<br />](https://learnah.org/wp-content/uploads/2018/08/March_2016_v3_MS_-_Paper_3_CIE_Chemistry_A-level_2-0.jpg)
