2020 HCI Prelim Paper 3 Question Paper

This document consists of 26 printed pages and 2 blank pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 19S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 3 Free Response Questions Candidates answer on the Question Paper Additional Materials: Data Booklet 9729/03 15 September 2020 2 hours READ THESE INSTRUCTIONS FIRST Write your name, CT group, centre number and index number clearly in the spaces above. Write in dark blue or black pen. You may use a 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 the questions. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. 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 / 25 2 / 16 3 / 19 Circle your option below 4 / 5 / 20 Deductions Total / 80

2 © Hwa Chong Institution 2020 9729/03/C2Prelim 2020 [Turn over Section A Answer all the questions in this section. 1 To date, the COVID-19 pandemic has infected more than 1 8 million people. The disease is caused by the SARS -CoV-2 coronavirus, whose general structure is shown in Fig. 1.1, with some of its parts labelled. Fig. 1.1 For Examiner's use (a) The spike proteins on the surface of the virus’ membrane facilitate the entry of the virus into the host cell. The tripeptide below was obtained from partial hydrolysis of the spike proteins. (i) Draw the structures of the organic products obtained when the tripeptide is hydrolysed completely by heating with H2SO4(aq). [3] (ii) Using one of the products from (i) and the aid of a suitable drawing, explain why it exhibits enantiomerism. [2] (iii) Explain why the virus will no longer be able to enter the host cell if the amino acids in the protein sequence were swapped with their enantiomers. [1] ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… spike protein lipid membrane

3 © Hwa Chong Institution 2020 9729/03/C2Prelim 2020 [Turn over ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… For Examiner's use

4 © Hwa Chong Institution 2020 9729/03/C2Prelim 2020 [Turn over (b) The transmission of COVID-19 may be mitigated by the u se of hand sanitisers, frequent washing of hands with soap and water, or wearing of N95 masks. For Examiner's use (i) The structure of the phospholipid particles that make up the lipid membrane of the virus is shown below in Fig. 1.2. Fig. 1.2 The alcohol content in hand sanitisers destroy the lipid membrane by initially forming hydrogen bonds with it. On Fig. 1.2 above, illustrate a hydrogen bond formed between an ethanol molecule and a phospholipid particle. [2] (ii) The structure of a soap particle is shown below. Describe the chemical interactions between the soap particle and the lipid membrane, and hence suggest how soap and water together break up the membrane of the virus. [2] (iii) Contrary to common belief, N95 masks do not work like filters. Instead the fibers that make up the fabric of the mask are permanently charged on the surface. This allows the fiber to capture dust in the air or droplets that contain the coronavirus. The surface of the fibers may be positively or negatively charged depending on the manufacturing method. An example of a strand of positively charged fiber is shown in Fig. 1.3. Fig. 1.3 Assuming that dust particles behave like non -polar simple molecules, describe the chemical interactions that form between the fiber and dust particles. Explain how these interactions arise. [2]

5 © Hwa Chong Institution 2020 9729/03/C2Prelim 2020 [Turn over ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… For Examiner's use (c) Another area of interest is the study of how long coronaviruses can survive on surfaces. It was found that coronaviruses have a far shorter life span on copper metal than many other surfaces. Describe the structure and bonding present in copper metal. [2] ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….……………………………………………… ……………………………………………………….………………………………………………

6 © Hwa Chong Institution 2020 9729/03/C2Prelim 2020 [Turn over (d) Many falsehoods surfaced during the pandemic, one of which is the claim that malaria drugs chloroquine and hydroxychloroquine are effective against the disease. This claim has not been verified in any controlled studies. A proposed synthesis route for chloroquine is shown below in Fig. 1.4. Fig. 1.4 For Examiner's use (i) Draw the structure of P. [1] (ii) Suggest reagents and conditions for steps 2 to 4, and draw the structures of compounds R and S. [5] (iii) Describe and explain how the basicity of the nitrogen functional group labelled N a would compare to that labelled Nb. [3] (iv) Describe a simple chemical test to distinguish between chloroquine and hydroxychloroquine, giving observations for each compound. [2]