2022 HCI Prelim P3 Question Paper

This document consists of 30 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 21S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 3 Free Response Candidates answer on the Question Paper. Additional Materials: Data Booklet 9729/03 14 September 2022 2 hours READ THESE INSTRUCTIONS FIRST Write your Centre number, index number, name and CT group in the spaces at the top of this page. 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. 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. No. of sheets of writing paper submitted (write 0 if none) For Examiner’s Use 1 / 16 2 / 23 3 / 21 Circle your option below 4 / 5 / 20 Deductions Total / 80

2 © Hwa Chong Institution 2022 9729/03/C2 Preliminary Exam [Turn over Section A Answer all the questions in this section. 1 (a) Shakudo is a Japanese alloy of copper and gold (typically 4–10% gold; the gold content is varied to control the colour of the alloy). Historically, Shakudo was used to construct or decorate Japanese sword fittings and small ornaments. DO NOT WRITE IN THIS MARGIN (i) A sample of Shakudo was analysed and found to contain two stable isotopes of copper. Table 1.1 isotope % abundance 63Cu 74.1% nCu 25.9% Using information from Table 1.1 and the relative atomic mass, Ar, of copper from the Periodic Table, calculate the value of n. Give your answer to the nearest integer. [1] (ii) Isotopes differ in their nucleon number. What do you understand by the term nucleon number? [1] (iii) Copper has electrons in the d orbitals. The d orbitals have two kinds of shapes. Draw diagrams to illustrate the two kinds of shapes for the d orbitals. Include x, y and z axes and label the d orbitals that you have drawn. [2] ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….…………………………………………

3 © Hwa Chong Institution 2022 9729/03/C2 Preliminary Exam [Turn over (b) A piece of Shakudo was suspected to contain small amounts of zinc. In an electrolysis experiment, this piece of Shakudo was made the anode and a thin piece of pure copper was made the cathode. An aqueous solution of copper(II) sulfate was used as the electrolyte. DO NOT WRITE IN THIS MARGIN (i) Using the Eo data given below and relevant Eo data from the Data Booklet, explain what happens to the zinc and gold during the electrolysis. Au3+ + 3e− ⇌ Au Eo = +1.52 V [2] (ii) The electrolysis experiment was carried out for 12.0 minutes using a current of 1.10 A. The copper cathode increased in mass by 0.26 g. What value of Avogadro constant, L, do these figures give? [2] ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….…………………………………………

4 © Hwa Chong Institution 2022 9729/03/C2 Preliminary Exam [Turn over (c) Ethers have general formula R–O–R′, where R and R′ represent the alkyl or aryl groups. Propoxybenzene is an example of an ether. propoxybenzene DO NOT WRITE IN THIS MARGIN (i) The –CH2CH2CH3 chain behaves like an alkane. Explain why alkanes are unreactive. [1] (ii) Propoxybenzene reacts similarly to phenol, such as in the nitration reaction shown below. The nitration of benzene differs from that of propoxybenzene in two ways. Describe and explain these two differences in terms of the reaction conditions and organic products. [2] ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….…………………………………………

5 © Hwa Chong Institution 2022 9729/03/C2 Preliminary Exam [Turn over (d) Epoxyethane is a cyclic ether and the simplest epoxide: a three-membered ring consisting of one oxygen atom and two carbon atoms. A reaction scheme involving epoxyethane is shown in Fig. 1.1. Fig. 1.1 DO NOT WRITE IN THIS MARGIN Compounds P and Q give effervescence with sodium metal. Both compounds do not exhibit enantiomerism. P also gives a brick-red precipitate when warmed with Fehling’s solution. Q also gives effervescence with aqueous sodium carbonate. Suggest the structures for P, Q and R. [3] ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….………………………………………………

6 © Hwa Chong Institution 2022 9729/03/C2 Preliminary Exam [Turn over (e) Detergents can be made from epoxyethane. epoxyethane The initiation step involves homolytic fission of a C–O bond in epoxyethane, giving rise to a ‘double-ended’ free radical. A chain reaction then occurs. The reaction eventually produces a molecule that contains the following structure. ––––CH2CH2–O–CH2CH2–O–CH2CH2–O–CH2CH2–O–CH2CH2–O–CH2CH2–O–––– Suggest equations for the initiation step and the first propagation step. Include curly half-arrows for the initiation step. [2] DO NOT WRITE IN THIS MARGIN ..………………………..……………….…………………………………………………………… ..………………………..……