PRSS Sc(Chem) Paper 3 QP

/ • Pasir Ris Second�ry School I Name SECONDARY 4 EXPRESS PRELIMINARY EXAMINATION 2025 SCIENCE (PHYSICS, CHEMISTRY) SCIENCE (CHEMISTRY, BIOLOGY) Paper 3 Chemistry Wednesday 0800 - 0915 Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST I Class Write your name, class and register number on all the work you hand in. You may use a soft pencil for any diagrams, graphs, tables or rough working. Write in dark blue or black pen. Do not use staples, paper clips, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. I Register Ne>: 5086/03 5088/03 27 Aug 2025 1 hour 15 minutes You may lose marks if you do not show your working or if you do not use appropriate units. Section A Answer all questions. Write your answers in the spaces provided on the question paper. Section B Answer one question. Write your answers in the spaces provided on the question paper. A copy of the Data Sheet is printed on page 15. A copy of the Periodic Table is printed on page 16. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 16 printed pages, including the cover page. [Turn over PRSS_2025_S4E/SNA_PRELIM_SCI(CHEM)_S086/SOBB_P3 Section A Answer all questions in the spaces provided. Fig. 1.1 shows the electronic structures of five atoms, A, B, C, D and E. @ A B c D Fig. 1. 1 (a) Select the atom based on Fig. 1.1 to answer the following questions. Each letter may be used once, more than once or not at all. (i) The atom that is in Group 17 of the Periodic Table. (ii) The atom that has 13 protons. (iii) The atom that is a noble gas. (iv) The atom that forms a stable ion with a 2- charge. E [1] [1] [1] [1] (b) Complete Table 1.2 to show the number of electrons, neutrons and protons in the sulfur atom and oxide ion. Table 1. 2 number of electrons number of neutrons number of protons ��s 16 1:02- 10 [4] [Total: B] 2

2 PRSS_2025_S4E/SNA_PREUM_SCI(CHEM)_508615088_P3 Table 2.1. gives the boiling points of four alcohols. Table 2.1 alcohol boiling point I •c butanol 117 ethanol 79 pentanol 138 propanol 97 Fig. 2.2 shows the set-up that can be used to obtain propanol from a mixture containing the four alcohols. p ... __ (a) Name this method of separation. (b) State the purpose of the apparatus labelled P and Q. p Q .. 1dd \ . \ alcohol collected [1] [2] (c) Explain why it is safer to heat the mixture of alcohols in the set-up shown in Fig. 2.2 rather than with a Bunsen burner. [1] (d) Explain why the set-up in Fig. 2.2 cannot be used to obtain butanol and pentanol from the mixture. [1] [Total: 5] 3 3 PRSS_2025_54E/SNA_PRELIM_SCI(CHEM)_508615088_P3 A solution of hydrochloric acid has a concentration of 1.5 molidm'- The graph in Fig. 3.1 shows how the temperature of the mixture varies with the volume of aqueous sodium hydroxide