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CIE Jun 2016 v3 Paper 3 Q1
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![You will determine the concentration of a solution of hydrochloric acid by diluting it and then titrating the diluted solution against an alkali. PMT HCl (aq) + NaOH(aq)NaCl (aq) + H2O(l) FA 1 was made by dissolving 1.06 g of sodium hydroxide, NaOH, in distilled water to make 250 cm3 of solution. FA 2 is hydrochloric acid, HCl. bromophenol blue indicator (a) MethodPipette 25.0 cm3 of FA 2 into the 250 cm3 volumetric flask. Keep remaining FA 2 for use in Question 2. Add distilled water to make 250 cm3 of solution and shake the flask thoroughly. Label this solution FA 3. Fill the burette with FA 3. Use the second pipette to transfer 25.0 cm3 of FA 1 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 yellow colour.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 3 added in each accurate titration. The rough titre iscm3. II III IV VI VII [7] (b) From your accurate titration results, obtain a suitable value for the volume of FA 3 to be used in your calculations. Show clearly how you obtained this value.UCLES 2016 9701/33/M/J/16 25.0 cm3 of FA 1 requiredcm3 of FA 3. [1]<br />
PMT (c) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (i) Calculate the concentration, in mol dm3, of sodium hydroxide in FA 1. Use the data in the Periodic Table on page 12. (ii) Calculate the number of moles of sodium hydroxide present in 25.0 cm3 of FA 1. concentration of NaOH in FA 1 =mol dm3 (iii) Deduce the number of moles of hydrochloric acid present in the volume of FA 3 you have calculated in (b). moles of NaOH =mol (iv) Calculate the concentration, in mol dm3, of hydrochloric acid in FA 2. moles of HCl =mol concentration of HCl in FA 2 =mol dm3 [5] [Total: 13]UCLES 2016 9701/33/M/J/16 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/June_2016_v3_QP_-_Paper_3_CIE_Chemistry_A-level_1-0.jpg)
![Page 2 Question Cambridge International AS/A LevelMay/June 2016 9701 33 Mark Scheme Syllabus Paper Indicative material Mark Total (a) I Two burette readings and titre value given for the rough titre and initial and final burette readings for two (or more) accurate titrations II Titre values recorded for accurate titrations and Appropriate headings for the accurate titration table and cm3 units.initial / start burette reading / volume / value final / end burette reading / volume / value titre or volume / FA 3 and used / added unit: / cm3 or (cm3 ) or in cm3 (for each heading) III All accurate burette readings are to the nearest 0.05 cm3. Do not award this mark if: 50(.00) is used as an initial burette readingmore than one final burette reading is 50.(00)any burette reading is greater than 50.(00) there is only one accurate titration. IV There are two uncorrected accurate titres within 0.10 cm3Do not award this mark if, having performed two titres within 0.10 cm3, a further titration is performed which is more than 0.10 cm3 from the closer of the initial two titres, unless a further titration, within 0.10 cm3 of any other, has also been carried out.Do not award the mark if any accurate burette readings (apart from initial 0 cm3) are given to zero dp. V, VI and VII Examiner rounds any burette readings to the nearest 0.05 cm3, checks subtractions and then select the best titres using the hierarchy:two (or more) accurate identical titres, then two (or more) accurate titres within 0.05 cm3, then two (or more) accurate titres within 0.10 cm3, etc. These best titres should be used to calculate the mean titre, expressed to nearest 0.01 cm3. Examiner calculates the difference ( ) between the mean titres obtained by the candidate and the Supervisor. Accuracy marks are awarded as shown. Award V,VI and VII for0.20 (cm3) Award V and VI for 0.20 <0.40 (cm3) Award V, only, for 0.40 <0.80 (cm3)Cambridge International Examinations 2016 [7]<br />
Page 3 Question (b) Cambridge International AS/A LevelMay/June 2016 9701 33 Mark Scheme Syllabus Paper Indicative material Candidate must take the average of two (or more) titres that are within a total spread of not more than 0.20 cm3. Working / explanation must be shown or ticks must be put next to the two (or more) accurate readings selected. The mean should be quoted to 2 dp, and be rounded to nearest 0.01 cm3. Two special cases, where the mean need not be to 2 dp:Allow mean expressed to 3 dp only for 0.025 or 0.075 (e.g. 26.325 cm3)Allow mean expressed to 1 dp, if all accurate burette readings were given to 1 dp and the mean is exactly correct. (e.g. 26.0 and 26.2 = 26.1 is allowed) (e.g. 26.0 and 26.1 = 26.1 is wrongshould be 26.05) Note: the candidates mean will sometimes be marked correct even if it was different from the mean calculated by the Examiner for the purpose of assessing accuracy. Mark Total [1] [5] [13] [2] (c) (i) (1.06/40)4 = 0.106 (ii) (iii) (iv) Correctly calculates n(NaOH) = 0.106(25/1000) = 0.00265 and n(HCl) = 0.00265 concentration FA 3 = 0.002651000/(b) concentration FA 2 = concentration FA 310 All answers correct to 3 or 4 sf (minimum of 3 parts attempted) Question 1 (a) Table for results withUnambiguous headings and correctly displayed unitsBalance readings recorded to same no of dpOne or two measuring cylinder readings recorded (does not have to include volume collected)Unit: / g or (g) or in g (for each heading), allow grams / grammes for g) and / cm3 or (cm3 ) or in cm3 (for each heading)Calculates volume of gas/mass FA 4 to 3 sf. Calculated value within 20% of supervisor value (b) (i) Correctly calculatesn(gas) = correct vol gas24 000 to minimum 2 sf and (ii)same number of moles of M2CO3 (iii) Mr = correct mass from (a)(ii)Cambridge International Examinations 2016<br />](https://learnah.org/wp-content/uploads/2018/08/June_2016_v3_MS_-_Paper_3_CIE_Chemistry_A-level_1-0.jpg)
