NJC_2022_H2_Chemistry_Prelim_P4_Ans

1 NJC SH2 Prelim Exam 9729 / 04/ 22 [Turn over NATIONAL JUNIOR COLLEGE SH2 Year-End Practical Examination Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 4 Practical Candidates answer on the Question paper Additional Materials: As listed in the Confidential Instructions 9729/04 16 August 2022 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 22 and 23. At the end of the examination, fasten all your work se curely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 23 printed pages including this cover page. Shift Laboratory For Examiner’s use 1 / 9 2 / 21 3 / 17 4 / 8 Total / 55

2 NJC SH2 Prelim Exam 9729 / 04/ 22 [Turn over Answer all the questions in the spaces provided. 1 Determination of the enthalpy change of a reaction, Hr FA 1 is 1.00 mol dm–3 sodium hydrogen carbonate, NaHCO3 (to be used for Q3 as well) FA 2 is 2.00 mol dm–3 sodium hydroxide, NaOH FA 3 is 2.00 mol dm–3 sulfuric acid, H2SO4 An acid -base neutralisation reaction involves reacting the two solutions, to produce water molecules. The equation for this neutralisation reaction is given below. H+(aq) + OH–(aq) → H2O(l) You will follow the instructions to perform two experiments, Experiment A and Experiment B. Record your results in Tables 1.1 and 1.2. Experiment A Reaction between FA 1, NaHCO3, and FA 2, NaOH. Reaction 1 NaHCO3(aq) + NaOH(aq) → Na2CO3(aq) + H2O(l) ΔHreaction1 The molar enthalpy change for reaction 1 , Δ Hreaction1, is the enthalpy change when 1.00 mol of NaHCO3 reacts completely with NaOH. 1 Using a 50 cm3 measuring cylinder, transfer 30.0 cm3 of FA 1 into a Styrofoam cup. Place this cup inside a second Styrofoam cup, which is placed in a 250 cm3 glass beaker. Place the lid on the cup. 2 Stir and measure the temperature of this FA 1, TFA1. 3 Using another 50 cm3 measuring cylinder, measure 20.0 cm3 of FA 2. 4 Stir and measure the temperature of this FA 2, TFA2. 5 Add FA 2 from the measuring cylinder to the FA 1 in the Styrofoam cup. Immediately replace the lid. 6 Using the thermometer, stir the mixture continuously until a maximum temperature is