TKGS 2024 Chem Prelim P2 QP

TANJONG KATONG GIRLS’ SCHOOL PRELIMINARY EXAMINATION SECONDARY FOUR EXPRESS CANDIDATE NAME CLASS 4 INDEX NUMBER CHEMISTRY 6092/02 Paper 2 12 August 2024 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, index number and name on all 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. DO NOT WRITE ON ANY BARCODES. Section A Answer all questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. 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 26. The use of an approved scientific calculator is expected, where appropriate. For Examiner’s Use Section A Setter : Ms Vina Ng Markers : Mrs Lee Suan Ching, Ms Esther Foo, Mrs Chan Liying, Ms Vina Ng Section B Total / 80 This document consists of 26 printed pages.

2 Tanjong Katong Girls’ School Sec 4 Preliminary Examination 2024 Section A Answer all questions. 1 (a) Fig. 1.1 shows part of the Periodic Table. He C N O F Ne S Cl Ar Br Kr Fig. 1.1 Select elements from Fig. 1.1 to answer the following questions. You may use each element once, more than once or not at all. Write down the symbol for an element which: (i) exists as diatomic molecules, ………………………………………………………………………………….[1] (ii) is a noble gas, ………………………………………………………………………………….[1] (iii) has seven electrons in its outer shell. ………………………………………………………………………………….[1]

3 Tanjong Katong Girls’ School Sec 4 Preliminary Examination 2024 (b) Some versions of the Periodic Table place hydrogen in Group 1 (Fig. 1.2). Other versions place hydrogen alone and not with any other group (Fig. 1.3). Fig. 1.2 Fig. 1.3 (i) Give one similarity between hydrogen and the elements in Group 1. …………………………………………………………………………………….. ………………………………………………………………………………….[1] (ii) Give one property of hydrogen that does not fit with the properties of the elements in Group 1. …………………………………………………………………………………….. ………………………………………………………………………………….[1] (iii) Hydrogen is in Period 1 of the Periodic Table. Explain why Period 1 only contains 2 elements. …………………………………………………………………………………….. ………………………………………………………………………………….[1] (c) Hydrogen is used to make margarine from vegetable oil. Describe, in terms of bonds, what happens when hydrogen reacts with vegetable oil. ……………………………………………………………………………………………. ………………………………………………………………………………………….[2] [Total: 8]

4 Tanjong Katong Girls’ School Sec 4 Preliminary Examination 2024 2 (a) There is a universal way for describing atoms across all scientific disciplines. In this system, t he nuclide of an element is represented by the atomic symbol, atomic number and the nucleon number. Naturally occurring lithium contains the isotopes Li3 6 and Li3 7 . (i) What is meant by the term, nucleon number? ………………………………………………………………………………….[1] (ii) The isotopes Li3 6 and Li3 7 have accurate isotopic masses of 6.015 and 7.016 respectively. The Ar of lithium is 6.942. Calculate the relative percentage abundances of the two isotopes, to two decimal places. [2]

5 Tanjong Katong Girls’ School Sec 4 Preliminary Examination 2024 (iii) A nuclear reaction is a reaction in which there is a change to an atomic nucleus. An experimental nuclear reactor uses Li3 6 and deuterium, H1 2 , as a fuel. Three nuclear reactions between these two atoms are described below (p+ is a proton; n is a neutron). The number of protons and neutrons must be conserved in each reaction. Li3 6 + H1 2 → 2 He 2 4 Li3 6 + H1 2 → He 2 4 + X + n Li3 6 + H1 2 → Y + p+ Suggest the identities of X and Y. [2]

6 Tanjong Katong Girls’ School Sec 4 Preliminary Examination 2024 (b) Aqueous copper(II) sulfate was electrolysed in two cells using different electrodes as shown in cells 1 and 2. (i) Write ionic equations for the reactions at the positive electrodes. Cell 1 ………………………………………………………………………….[1] Cell 2 ………………………………………………………………………….[1] (ii) Describe the change that would be seen at the negative electrode in both cells. …………………………………………………………………………………….. ………………………………………………………………………………….[1] (iii) Describe the changes that would be seen in Cell 1, but not in Cell 2. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ………………………………………………………………………………….[2] [Total: 10] carbon electrode aqueous copper(II) sulfate copper electrode aqueous copper(II) sulfate Cell 1 Cell 2

7 Tanjong Katong Girls’ School Sec 4 Preliminary Examination 2024 3 (a) Salts that are insoluble in water are prepared by precipitation. Describe how you will prepare a pure and dry sample of lead(II) iodide, PbI2, by precipitation. Your answer should include: • starting reagents that you would use • practical details • an ionic equation for the precipitation reaction. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………….[4] (b) A student observed the reaction of hydrochloric acid with four different metals. The student used the same concentration and volume of hydrochloric acid and the same mass of metal in each experiment. Table 3.1 metal observations cobalt dissolved very slowly and a few bubbles produced iron dissolved slowly and few bubbles produced slowly magnesium dissolved very quickly and many bubbles produced very rapidly zinc dissolved quickly and many bubbles produced rapidly Use the information in Table 3.1 to suggest the order of reactivity of these metals. most reactive ……………. , …………. , …………. , …………. least reactive [2]

8 Tanjong Katong Girls’ School Sec 4 Preliminary Examination 2024 (c) Magnesium oxide is classified as a basic oxide, but zinc oxide is classified as an amphoteric oxide. Explain the meaning of the terms basic and amphoteric as applied to these oxides. Include one equation in your explanation. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………….[2] [Total: 8]

9 Tanjong Katong Girls’ School Sec 4 Preliminary Examination 2024 4 (a) (i) Potassium fluoride is a white crystalline solid with a melting point of 860C. It dissolves in water to form a solution which conducts electricity. Silicon dioxide is a white crystalline solid with a melting point of 1715 C. It does not conduct electricity in the solid state nor in the liquid state. It is insoluble in water. Name the type of structure and d