2023 ACSI Chemistry Y4 Prelim p3

1 Anglo-Chinese School (Independent) 2023 Preliminary Examination Year 4 Express 6092/3 [Turn over Year 4 Express Preliminary Examination 2023 CHEMISTRY PAPER 3 Practical 6092/3 Thursday 31 July 2023 1 hour 50 minutes Candidates are to write their answers on the Question Paper. READ THESE INSTRUCTIONS FIRST Write your Candidate number in the space at the top of this page and on any separate answer paper used. Write in dark blue or black pen on both sides of the paper. You may use a 2B pencil for any diagrams or graphs. Do not use paper clips, glue or correction fluid. Answer all questions in all the spaces provided. The use of an approved scientific calculator is expected, where appropriate. You should show the essential steps in any calculation and record experimental results. Qualitative analysis notes are printed on page 10. 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. This question paper consists of 10 printed pages. Shift Laboratory For Examiner’s Use 1 2 3 Total /40 Candidate Name : Index No. :

2 Anglo-Chinese School (Independent) 2023 Preliminary Examination Year 4 Express 6092/3 [Turn over 1 Acids of general formula HYO3 are known, where Y can be nitrogen, phosphorus, chlorine or bromine. P is a solution of one of these acids containing 3.75 g in 500 cm3. Q is 0.100 mol/dm3 sodium hydroxide. You are to identify Y by titrating Q with P. a Put solution P into the burette. Pipette a 25.0 cm3 (or 20.0 cm3) portion of Q into a flask and titrate with P using the indicator provided. Record your titration results in the space provided, repeating the titration as many times as you consider necessary to achieve consistent results. Results [5] b From your titration results, obtain an average volume of P to be used in your calculations. Show clearly how you obtained this volume. [1] Average volume of P

3 Anglo-Chinese School (Independent) 2023 Preliminary Examination Year 4 Express 6092/3 [Turn over c Q is 0.100 mol/dm3 sodium hydroxide. One mole of the acid HYO3 reacts with one mole of sodium hydroxide. Using the titration results, calculate the concentration, in mol/dm3 of the acid HYO3 present in solution P. [2] Concentration of HYO3 in P = d P is aqueous HYO3 which contains 3.75 g in 500 cm3. Using your answer to (c), calculate the relative molecular mass of HYO3. [2] Relative molecular mass of HYO3 = e Complete the table below. The relative atomic masses of hydrogen and oxygen are 1 and 16 respectively. [1] Element Relative atomic mass Formula of its acid HYO3 Relative molecular mass of its acid Bromine (Br) 80 HBrO3 Chlorine (Cl) 3