GESS 4Exp Pure Chem Prelim 2024_P2

This document consists of 23 printed pages. GAN ENG SENG SCHOOL Preliminary Examination 2024 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Candidates answer on the Question Paper. No Additional Materials are required. 6092/02 21 August 2024 1 hour 45 minutes READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. 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. Section A Answer all questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 23. The use of an approved scientific calculator is expected, where appropriate. For Examiner‘s Use Section A 70 Section B 10 Q9 Q10 Total 80 *Circle where appropriate

GESS 4EXP Chemistry 6092/02 PRELIM 2024_JAN 2 Section A Answer all questions. 1 The equations below show reactions involving elements A to E. Element A: 2 A + 2 H2O → 2 AOH + H2 Element B: BO2 + 2 NaOH → Na2BO3 + H2O Element C: C2 + 2 Br– → 2 C– + Br2 Element D: D + Cu2+ → D2+ + Cu Element E: E2O3 + 6 H+ → 2 E3+ + 3 H2O Each letter represents an element found in Period 3 of the Periodic Table (sodium to argon). The letters do not represent the actual symbols of the elements. (a) Identify elements A to E. A …………………… B …………………… C …………………… D …………………… E …………………… [5] (b) Classify each element as having undergone oxidation, reduction or neither. Put a tick (ü) in each row. element undergone oxidation undergone reduction neither oxidised nor reduced A B C D E [3] [Total: 8]

GESS 4EXP Chemistry 6092/02 PRELIM 2024_JAN 3 2 Gas chromatography can be used to separate a mixture of gases as shown below. The retention time is the time it takes each component to travel through the column. (a) The gases entering the column must be dry to avoid interference from water molecules. Suggest how the gases may be dried. …………………………………………………………………………………………….. [1] (b) Vegetable oils can be changed into bio-diesel for use in diesel engines. Gas chromatography is used to identify the methyl esters in a sample of bio-diesel. The table shows the retention time for three methyl esters. methyl ester Mr retention time / min lauric 214 1.6 palmitic 270 3.1 stearic 298 3.9 One factor affecting retention time is the rate of diffusion. (i) The data in the table suggests a correlation between the relative molecular mass and the retention time. Describe this correlation. ……………………………………………………………………………………. ……………………………………………………………………………………. [1]

GESS 4EXP Chemistry 6092/02 PRELIM 2024_JAN 4 (ii) The experiment is repeated with the column at a