2025 DHS H2 Chem Prelim P4_QP

This question paper consists of 20 printed pages. © DHS 2025 9729/04 [Turn over Name: Centre/Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination Year 6 H2 CHEMISTRY Paper 4 Practical Candidates answer on the Question Paper. 9729/04 25 August 2025 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your centre number, index number, name and class at the top of this page. Give details of the practical shift and laboratory where appropriate, in the boxes provided. Write in dark 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 sci entific 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. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 26 2 18 3 11 Total 55

2 © DHS 2025 9729/04 Answer all questions in the spaces provided. 1 Determination of the concentrations of two solutions by graphical analysis Sulfuric acid is a strong acid which neutralises sodium hydroxide in an exothermic reaction as shown in equation 1. equation 1 H2SO4 + 2NaOH → Na2SO4 + 2H2O In this question, you will prepare six mixtures, each containing the same total volume of solution but with different volumes of sulfuric acid and sodium hydroxide added. For each mixture, you will measure the temperature change. Graphical analysis of your results will enable you to determine the concentration s of the sulfuric acid and of the sodium hydroxide used. FA 1 is aqueous sodium hydroxide, NaOH. FA 2 is aqueous sulfuric acid, H2SO4. (a) Prepare a table in the space provided on page 4 in which to record, to an appropriate degree of precision: • the volumes of FA 1 (VFA 1) and FA 2 (VFA 2) used • all values of temperature TFA 1, TFA 2, Tave, Tmax and Tmax Experiment 1 1. Using a measuring cylinder, transfer 10.0 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. 2. Place the thermometer into the FA 1 in the cup. Tilt the cup if necessary to ensure the bulb of the thermometer is fully covered. Record the temperature of FA 1, TFA 1. 3. Using another measuring cylinder, measure 60.0 cm3 of FA 2. 4. Rinse and dry the thermometer. Measure and record the temperature of FA 2, TFA 2. 5. Add the FA 2 from the measuring cylinder to the FA 1 in the Styrofoam cup. 6. Using the thermometer, stir the mixture continuously until it reaches its maximum temperatur