2021 NJC Prelims Paper 4_Answers Final

1 NJC SH2 Preliminary Examination 9729/04/21 NATIONAL JUNIOR COLLEGE SH 2 Year − End Practical Examination Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 4 Practical Candidate answer on the Question paper. 9729/04 Tuesday 17 August 2021 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your identification number and name. Give details of the practical shift and laboratory where appropriate, in the boxes provided. Write in blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. Qualitative Analysis Notes are printed on pages 19 and 20. The number of marks is given in brackets [ ] at the end of each question or part question. This paper consists of 20 printed pages including this cover page. Shift Laboratory For Examiner’s use 1 / 15 2 / 15 3 / 14 4 / 10 Presentation /1 Total / 55 Presentation [1] shows appropriate units and 3 or 4 sf in all final ans in Q1 & 2. Any calculations not attempted loses this mark.

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3 NJC SH2 Preliminary Examination 9729/04/21 [Turn over 1 Determination of the concentration of a solution of sodium hydroxide and the enthalpy change of neutralisation, 'Hn FA 1 is 1.0 mol dm−3 sulfuric acid, H2SO4. FA 2 is a solution of sodium hydroxide, NaOH, of unknown concentration. According to the Arrhenius theory of acids and bases, an acid produces H+(aq) ions and a base produces OH–(aq) ions, in aqueous solution. Using the Arrhenius theory, an acid-base neutralisation reaction involves reacting these two ions together to produce water molecules. The equation for this neutralisation reaction is given below. H+(aq) + OH(aq) → H2O(l) 'Hn In this question, you will carry out a series of experiments where different volumes of FA 1 and FA 2 are mixed together. You will determine the temperature change of the mixture, 'T of each experiment and then analyse your results graphically in order to determine the x concentration of NaOH in FA 2 x maximum temperature change, 'Tmax x value for the enthalpy change of neutralisation, 'Hn

4 NJC SH2 Preliminary Examination 9729/04/21 (a) M