GESS 4Exp Pure Chem Prelim 2024_P3

This document consists of 13 printed pages. GAN ENG SENG SCHOOL Preliminary Examination 2024 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 3 Candidates answer on the Question Paper. No Additional Materials are required. 6092/03 5 August 2024 1 hour 50 minutes READ THESE INSTRUCTIONS FIRST Write your class, index number and name on all the work you hand in. 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, highlighters, glue or correction fluid/tape. 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 page 12. The Periodic Table is provided on page 13. The number of marks is given in brackets [ ] at the end of each questions or part question. Shift Laboratory For Examiner’s Use Q1 17 Q2 18 Q3 5 Total 40

GESS 4EXP Chemistry 6092/03 PRELIM 2024_JAN 2 1 Sodium carbonate reacts with dilute sulfuric acid. This reaction is exothermic. In this experiment you will determine the percentage purity of a sample of impure anhydrous sodium carbonate. You will measure the enthalpy change of reaction when a sample of impure anhydrous sodium carbonate reacts with excess dilute sulfuric acid. Read all the instructions carefully before starting the experiments in Question 1. Instructions X is a sample of the impure anhydrous sodium carbonate. Y is 1.00 mol/dm3 dilute sulfuric acid, H2SO4 (a) • Weigh the container with X. Record this mass. mass of container with X = .................... g • Support the Styrofoam cup in the 250 cm3 beaker. • Use the measuring cylinder to place 25 cm3 of Y into the cup. • Measure the temperature of Y. Record this temperature at time = 0 in the table below. • Start the stopwatch and leave it running for the whole experiment. • Measure the temperature of Y every minute for 2 minutes. Record the temperatures in the table below. • At 3 minutes transfer X from the container into the cup. Stir the contents and continue to measure, and record, the temperature every minute up to 8 minutes. Results time/min 0 1 2 3 4 5 6 7 8 temperature/ºC • Reweigh the container with any residual solid. Record this mass. mass of container with residual X = .................... g [3]

GESS 4EXP Chemistry 6092/03 PRELIM 2024_JAN 3 (b) (i) Plot your results on the grid with temperature on the y-axis and time on the x-axis. Complete the graph by drawing two straight lines of best fit. One line should be drawn using data from 0 to 2 minutes and the other line should be drawn using data from 4 to 8 minutes. Extend both of these lines to 3 minutes. Draw a vertical line at 3 minut