YSS 4E Pure Chem Paper 2 Prelim 2024

[Turn over YISHUN SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 SECONDARY 4 EXPRESS CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 6092/02 Paper 2 23 August 2024 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, class and index number on 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. Section A Answer all questions in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. Electronic calculators may be used. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 24. The use of an approved scientific calculator is expected, where appropriate. This document consists of 24 printed pages.

2 Section A Answer all questions. 1 Use the list of substances to answer the following questions. calcium chloride zinc helium sodium chloride graphite copper sodium copper(II) carbonate You may use each substance once, more than once or not at all. (a) Which substance has a giant covalent structure? .........………………………………………………………………………………………………….[1] (b) Which substance only conducts electricity in molten state? .........………………………………………………………………………………………………….[1] (c) Which substance can be decomposed by heat to give a gaseous product at room temperature and pressure? .........………………………………………………………………………………………………….[1] (d) Which two substances form the alloy brass? .........………………………………………………………………………………………………….[1] (e) Which substance is a noble gas? .........………………………………………………………………………………………………….[1] (f) Which substance can be oxidised by oxygen to form an amphoteric oxide? .........………………………………………………………………………………………………….[1] [total: 6]

3 [Turn over 2 Fig. 2.1 shows two different experimental set up for electroplating an object with silver. Fig. 2.1 (a) Write equations, with state symbols, to show the reactions that happen at the anode and cathode during each experiment. experiment 1 anode: .........…………………………………………………………………………………………… cathode: .........………………………………………………………………………………………… experiment 2 anode: .........…………………………………………………………………………………………… cathode: .........………………………………………………………………………………………[3] (b) At the beginning of each experiment, the student removes a sample of the electrolyte, aqueous silver nitrate, and puts it into separate test tubes. The student then adds a few drop of aqueous sodium chloride to each test tube. Describe and explain what the student would see. .........…………………………………………………………………………………………………..... .........………………………………………………………………………………………………….[1] cathode object to be plated aqueous silver nitrate AgNO3(aq) AgNO3 (aq) anode carbon rod oxygen gas experiment 1 experiment 2 silver rod anode cathode object to be plated aqueous silver nitrate AgNO3(aq) AgNO3 (aq)

4 (c) After some time, the student observes that no more silver is being deposited on the object in experiment 1 but more silver is being deposited on the object in experiment 2. Suggest a reason for this observation in both experiments 1 and 2. .........…………………………………………………………………………………………………..... .........…………………………………………………………………………………………………..... .........………………………………………………………………………………………………….[2] (d) In Fig. 2.2, an iron object is placed in a beaker of aqueous silver nitrate, a silver coating forms on the iron. If a gold object is placed in aqueous silver nitrate, no reaction happens. Fig. 2.2 Explain why. .........…………………………………………………………………………………………………..... .........…………………………………………………………………………………………………..... .........………………………………………………………………………………………………….[2] [total: 8] aqueous silver nitrate iron object beaker

5 [Turn over 3 (a) Minerals contain salts which are mainly ionic compounds. Examples include potassium sulfate, which is used as a fertiliser and lead(II) nitrate, which is used in coating photothermographic paper. (i) In Table 3.1, state the reagents which may be used to prepare the salts, potassium sulfate and lead(II) nitrate. Table 3.1 salt reagent 1 reagent 2 potassium sulfate lead(II) nitrate [2] (ii) Aqueous solutions of potassium sulfate and excess lead( II) nitrate were mixed to produce an insoluble salt. With the aid of a balanced chemical equation, calculate the mass of insoluble salt that can be obtained from the reaction when 15 cm3 of 2.0 mol/dm3 potassium sulfate solution is used. mass of salt = ………………………… g [3]

6 (b) More than 90 % of the Earth’s crust is composed of silicate minerals which contain metal ions ionically bonded to silicate ions. Examples of naturally occurring silicates are shown in Table 3.2. Table 3.2 name of silicate compound formula willemite Zn2SiO4 castorite LiAlSi4O10 chrysotile Mg3Si2O5(OH)4 (i) The formulae of silicate compounds are not simple. Some silicate compounds contain one type of metal, others contain more than one. All silicate ions contain silicon and oxygen. Both the numbers of the atoms and the charges on the ions vary. Give the formulae and charges of the silicate ions present in Table 3.2. willemite ................ castorite ................ chrysotile ................ [2] (ii) Albite is a silicon mineral that has the following percentage composition by mass. element percentage by mass sodium 8.7 % aluminium 10.3 % silicon 32.3 % oxygen 48.7 % Use the data to work out the empirical formula of albite. [2] [total: 9]

7 [Turn over 4 Flerovium, Fl (atomic number:114) was first made in research laboratories in 1999. (a) Flerovium was made by bombarding atoms of plutonium, Pu (atomic number: 94), with atoms of element Z. The nucleus of one atom of plutonium combined with the nucleus of one atom of element Z. This formed the nucleus of one atom of Flerovium. Suggest the identity of element Z. .........………………………………………………………………………………………………….[1] (b) With the use of the Periodic Table, complete Table 4.1 to fill in the missing information about an atom of flerovium. Table 4.1 number of electron shells number of valence electrons [1] (c) Two isotopes of Flerovium are 288 Fl and 289 Fl. State a similarity and difference between the two nuclei of the two isotopes. .........…………………………………………………………………………………………………..... .........…………………………………………………………………………………………………..... .........………………………………………………………………………………………………….[2]

8 (d) Only a relatively small number of atoms of flerovium has been made in the laboratory and the properties of flerovium have not yet been investigated. It has been suggested that flerovium behaves like a typical metal. (i) Draw a labelled diagram to show the type of bonding in flerovium. [2] (ii) State a physical property of flerovium. ........………………………………………………………....………………………………....[1] (iii) Suggest a chemical property of flerovium oxide. ........……………………………………………………………………....…………………....[1] [total: 8]

9 [Turn over 5 Chlorophyll, xanthophyll and phaeophytin are green pigments that may be found in leaves. Aged chlorophyll can decompose into phaeophytin, a grey pigment molecule. A student carried out a chromatographic experiment to compare the extracts of spinach leaves obtained from 2 different sourc