2023 ACJC H2 Chem Prelim Paper 3 QP

1 © ACJC2023 9729/03/Prelim/2023 [Turn over Anglo-Chinese Junior College JC2 Preliminary Examination Higher 2 CANDIDATE NAME FORM CLASS TUTORIAL CLASS INDEX NUMBER CHEMISTRY Paper 3 Free Response Candidates answer on the Question Paper. Additional Materials: Data Booklet 9729/03 28 August 2023 2 hours READ THESE INSTRUCTIONS FIRST Write your index number and name 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. Answer all questions in the spaces provided on the Question Paper. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all questions. Section B Answer one question. Circle the number of the question you have attempted. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. 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. For Examiners’ use only Section A 1 / 17 2 / 18 3 / 25 Section B 4 / 5 / 20 Total / 80 This document consists of 28 printed pages.

2 © ACJC2023 9729/03/Prelim/2023 [Turn over Section A Answer all the questions in this section. 1 Ibuprofen belongs to a class of drugs called non -steroidal anti-inflammatory drugs (NSAIDs) used to reduce inflammation, pain and fever. Pain, fever, and inflammation are caused by the release in the body of chemicals called prostaglandins. Ibuprofen blocks the enzyme that makes prostaglandins resulting in lower levels of prostaglandins. The following diagram shows the first step in the synthe sis route to form ibuprofen from compound A. (a) A series of experiments were carried out at 25 °C to find the effect of initial concentration of hydrogen cyanide, cyanide ions and A on the initial rate of formation of B. Table 1.1 experiment initial concentration / mol dm−3 initial rate of formation of B / mol dm−3 s−1 [A] [HCN] [CN−] 1 0.020 0.060 0.060 1.00 2 0.020 0.050 0.050 0.833 3 0.020 0.050 0.060 1.00 4 0.025 0.050 0.050 1.042

3 © ACJC2023 9729/03/Prelim/2023 [Turn over (i) Write a balanced equation for the reaction that produces compound B. [1] (ii) Use the data in Table 1.1 to deduce the order of reaction with respect to each of the reactants. [3] (iii) Write the rate equation for this reaction. Hence, calculate the value of the rate constant using the data in experiment 2. Include its units. [2] (iv) Describe a mechanism that is consistent with the rate equation deduced in (a)(iii) and indicate which step in the mechanism is the rate determining step. Explain your reasoning. [3] ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ………………………………………………………………………………………………..

4 © ACJC2023 9729/03/Prelim/2023 [Turn over ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. (b) Explain, with the aid of a labelled Boltzmann distribution diagram, the effect on rate when the temperature is increased. [3] ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………

5 © ACJC2023 9729/03/Prelim/2023 [Turn over (c) Propose a 3 -step synthesis of ibuprofen starting from the compound 1-isobutyl-4-vinylbenzene. Suggest the reagents and conditions, and draw the structure of the organic intermediate product in each step. [5] ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… [Total: 17]

6 © ACJC2023 9729/03/Prelim/2023 [Turn over 2 (a) Describe and explain the general trend in the first ionisation energy across Period 3. [3] ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… (b) (i) Describe and explain the reactions, if any, of the chlorides NaC l, AlCl3 and PCl5 with water. Write equations for all reactions that occur and suggest the pH of the resulting solutions. [4] (ii) At certain temperatures, aluminium chloride exists as A l2Cl6 molecules. Draw the structure of Al2Cl6. Label the co-ordinate bonds on your structure. [1] ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ………………………………………………………………………………………………..

7 © ACJC2023 9729/03/Prelim/2023 [Turn over ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. (c) PCl5 reacts with ketones in a 1 : 1 molar ratio to give gem -dichlorides. A gem-di