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 added to a 25.0 cm3 sample of the hydrochloric acid. 0 10 20 30 40 volume of aqueous sodium hydroxide added I cm3 Fig. 3.1 (a) The chemical equation for the reaction between hydrochloric acid and aqueous sodium hydroxide is given below. NaOH(aq) + HCI(aq) - NaCI(aq) + H20(I) (i) Name the type of reaction between hydrochloric acid and aqueous sodium hydroxide. [1) (ii) Deduce the ionic equation, including state symbols, for the reaction between hydrochloric acid and aqueous sodium hydroxide. (b) (i) Using Fig. 3.1, state whether the reaction is endothermic or exothermic and determine the volume of aqueous sodium hydroxide added that gave the highest temperature reading. [2] (ii) Explain why the temperature of the mixture falls when the volume of aqueous sodium hydroxide added is more than the volume identified in (b)(i). [1] 4

PRSS_2025_S4E/5NA_PRELIM_SC/(CHEM)_508615088_P3 (c) (i) Calculate the number of moles of hydrochloric acid in 25.0 cm3 of the given sample. [1] (li) Based on the given equation in (a), what is the number of moles of sodium hydroxide which reacted with the hydrochloric acid in c(i)? [1] (iii) Use the information in (c)(i) and c(ii) to calculate the concentration of aqueous sodium hydroxide used to completely react with the hydrochloric acid added. [1] [Total: 9] 5 4 Fig. 4.1 shows the reactions of some substances. solution u r· excess aqueous ammonia I -I PRSS_2025_S4EISNA_PRELIM_SCI(CHEM)_50861508B_P3 pink-brown I solid P heated in which is a reducing agent R gas that extinguish es a lighted splint p' sound with a 'po blac� solid I add dilute nitric acid solutionS I warm wit aqueous gas that turns damp red litmus blue h aluminium and sodium hydroxide Fig. 4.1 (a) Identify the substances P, Q, R, and S. (i) p (ii) Q (iii) R (iv) S [4] (b) Write a balanced chemical equation, including state symbols, for any one of the reactions in Fig. 4.1. (c) State the colour of solution U. 6 [3] [1] [Total: 8]

5 PRSS_2025_S4E/5NA_PRELIM_SCI(CHEM}_50811/50BB_P3 A student investigates the reaction of small pieces of excess zinc carbonate with dilute sulfuric acid at 20 'C. (a) Fig. 5.1 show the volume of carbon dioxide gas released as the reaction proceeds. Ul 0) C) � 30 :a "C � � 20 0 Q) E :::> g 10 0 0 2 4 6 8 10 12 time/min Fig. 5.1 (i) Suggest why the volume of carbon dioxide gas remains the same after 10 minutes. 14 [1] (ii) Deduce the time taken from the start of the experiment to collect 20 cm3 of carbon dioxide gas. [1] (iii) The student repeats the experiment at 30 'C. All other conditions are kept the same. Draw a line on the grid in Fig. 5.1 to show how the volume of carbon dioxide gas changes with time when the reaction is carried out at 30 'C. [2] 7 PRSS_2025_S4E/5NA_PRELIM_SCI(CHEM}_50811/5088_P3 (b) The student repeats the experiment using zinc carbonate powder instead of small pieces of zinc carbonate. (c) Explain, in terms of collisions of particles, how the rate of reaction differs when zinc carbonate powder is used instead of pieces of zinc carbonate. (i) State the formula of the ion that is present in an aqueous solution of all acids. [2] [1] (ii) A few drops of Universal indicator was added to the reactants at the beginning of the experiment. State the colour change observed in the solution as the reaction proceeded. [1] [Total: B] 8

6 PRSS_2025_S4E/5NA_PRELIM_SCI(CHEM)_5086/50BB_P3 (a) Zinc oxide reacts with carbon monoxide to form zinc and carbon dioxide. ZnO(s) + CO(g)--+ Zn(g) + C02(g) (i) Explain, in terms of oxidation states, why the reaction between zinc oxide and carbon monoxide is a redox reaction. [2] (ii) Explain, in terms of bonding and structure, why zinc oxide exists as a solid while carbon monoxide exists as a gas at room temperature and pressure. (b) Table 6.1 compares the reactivity of zinc with that of three other metals. Table 6.1 metal reactivity with cold water reactivity with steam barium reacts rapidly � cobalt no reaction reacts slowly when heated magnesium reacts very slowly reacts rapidly zinc no reaction reacts easily when heated [3] (i) Use the information in Table 6.1 to arrange the four metals in order of their reactivity, from the least reactive to the most reactive. (ii) Zinc is found in Group 12 while lithium is found in Group 1 of the Periodic Table. [1] Describe one way in which the physical property of zinc differs from that of lithium. [1] [Total 7] 9 7 ) PRSS_2025_S4E/5NA_PRELIM_SCI(CHEM)_5086/50BB_P3 Hydrogen peroxide, H202, is a covalent compound. It decomposes to form water and oxygen. (a) Draw a 'dot-and-cross' diagram for a molecule of hydrogen peroxide. Show only the arrangement of the outer shell electrons. [Proton (atomic) number: H, 1; 0, 16] [2] (b) The decomposition of hydrogen peroxide involves a change from the liquid state to the gaseous state. Describe the difference in both the move