NJC 2024 H2_Chem_P4 Solutions

1 NJC SH2 Preliminary Examination 9729/04/24 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 Wednesday 28 August 2024 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 21 and 22. The number of marks is given in brackets [ ] at the end of each question or part question. This paper consists of 22 printed pages including this cover page. Shift Laboratory For Examiner’s use 1 / 14 2 / 20 3 / 12 4 / 9 Total / 55

2 NJC SH2 Preliminary Examination 9729/04/24 1 Determination of a value for an enthalpy change of solution Via Hess’s Law. FA 1 is solid sodium hydrogencarbonate, NaHCO3. FA 2 is 1.00 mol dm–3 sulfuric acid, H2SO4. Sodium hydrogencarbonate dissolves in water according to equation 1. equation 1 NaHCO3(s) + aq → Na+(aq) + HCO3–(aq) H1 Both solid and aqueous sodium hydrogencarbonate react with sulfuric acid. equation 2 2NaHCO3(s) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l) + 2CO2(g) H2 equation 3 2NaHCO3(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l) + 2CO2(g) H3 In this question, you will perform an experiment to determine a value for H2. You will use data provided to calculate H3 and hence a value for H1. (a) Determination of the molar enthalpy change of reaction, H2 In this experiment, you will determine the maximum temperature change when a known mass of solid sodium hydrogencarbonate, FA 1, reacts with excess dilute sulfuric acid, FA 2. In an appropriate format in the space provided on page 3, prepare tables in which to record for your experiment: • all weighings to an appropriate level of precision, • all values of temperature, T, to an appropriate level of precision. Procedure 1. Weigh the capped bottle containing FA 1. Record this mass. 2. Place one polystyrene cup inside another polystyrene cup and place both in a glass beaker. 3. Use a 50 cm3 measuring cylinder to transfer 30.0 cm3 of FA 2 into the polystyrene cup. 4. Stir the FA 2 in the polystyrene cup wi