2022 OPSS Chem Prelims P2

ORCHID PARK SECONDARY SCHOOL Preliminary Examination 2022 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY Paper 2 Secondary 4 Express Setter: Mr Goh Chye Joo 6092/02 24 August 2022 1 hour 45 minutes 80 Marks Additional Materials: Nil READ THESE INSTRUCTIONS FIRST Write your name, register number and class on all the work you hand in. Write in dark blue or black ink. 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 all three questions. The last question is in the form either/or. Answer all questions 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 18. The use of an approved scientific calculator is expected, where appropriate. This document consists of 18 printed pages. [Turn over

2 Section A Answer all questions in the space provided. The total mark for this section is 50. A1 This table shows some information about atoms of the elements L, M, N and O. (The letters do not represent the atomic symbols of the elements.) element atomic number number of protons number of neutrons mass number electronic configuration L 16 16 16 32 M 7 7 7 14 N 1 1 1 2 1 O 11 (a) (i) Complete the table by filling in the information of the four elements. [3] (ii) Give a reason why element O is likely to be a metal. ……………………………………………………………………..……………... ……………………………………………………………………………………. [1] (b) (i) Describe the change in electronic configuration that occurs to an atom of element M when it forms an ion. State the formula of ion formed using the chemical symbol M. ……………………………………………………………………..……………... ……………………………………………………………………………………. [2] (ii) The accurate relative atomic mass of element L is 32.1. Explain why this is not a whole number. ……………………………………………………………………..……………... ……………………………………………………………………………………. [1] (c) Draw a dot and cross diagram to show the bonding formed between element N and O. Show outer electrons only. [2]

3 A2 Iron is one of the most important metals. Most iron is used in the alloy steel. (a) Explain, in terms of metallic bonding, why iron is a good electrical conductor. …………………….………………………………………………...……………………. ……………………………………………………………………………………………. …………………….………………………………………………...……………………. ……………………………………………………………………………………………. [2] (b) Describe how different proportions of carbon can modify the physical properties of steel. …………………….………………………………………………...……………………. ……………………………………………………………………………………………. …………………….………………………………………………...……………………. ……………………………………………………………………………………………. [2] (c) When under water, iron pipes will rust relatively rapidly. (i) State the essential conditions needed for the rusting of iron. …………………….………………………………………………...…………… [1] (ii) Pieces of magnesium are often attached to under water pipes. Explain how the magnesium protects the iron pipes against rusting. …………………….………………………………………………...…………… …………………………………………………………………………………… …………………….………………………………………………...……………. …………………………………………………………………………………… [2] (d) A sample of a compound of iron is analysed. The sample contains 0.547 g of potassium, 0.195 g of iron, 0.252 g of carbon and 0.294 g of nitrogen. Calculate the empirical formula of this compound. empirical formula ………………………….. [2] [Turn over

4 A3 This question is about the Periodic Table. The table shows part of the original Periodic Table first published by Mendeleev in 1869. Period 1 Period 2 Period 3 Period 4 Period 5 Group 1 H Li Na K Cu Rb Ag Group 2 Be Mg Ca Zn Sr Cd Group 3 B Al * * Y In Group 4 C Si Ti * Zr Sn Group 5 N P V As Nb Sb Group 6 O S Cr Se Mo Te Group 7 F Cl Mn Br * I The asterisks ( * ) show gaps in the table that Mendeleev deliberately left. (a) Which group of elements in a modern Periodic Table is missing from Mendeleev’s Periodic Table? ……………………………………………………………………………………………. [1] (b) State two other differences between Mendeleev’s original table and a modern Periodic Table. …………………….………………………………………………...……………………. ……………………………………………………………………………………………. ……………………………………………………………………………………………. [2] (c) Find rubidium, Rb, in the Periodic table provided on page 18. Predict the reaction between rubidium and cold water. Include observations and the chemical equation. …………………….………………………………………………...……………………. ……………………………………………………………………………………………. …………………….………………………………………………...……………………. ……………………………………………………………………………………………. [3]

5 A4 A new type of electroplating is known as ‘brush electroplating’. It is used to electroplate zinc into very large iron supports to be used in buildings. The iron supports are too big to be plated in a normal electrolysis tank. During the process, a metal brush spreads a layer of aqueous zinc sulfate over the iron surface. A battery gives the brush a positive charge and gives the iron support a negative charge. A layer of zinc forms on the surface of the iron support. (a) (i) Other than the prevention of rusting, state another advantage of electroplating the iron support. …………………………………………………………………………………….. [1] (ii) Write an ionic half-equation, with state symbols, to represent the reaction at the cathode during the electrolysis. …………………………………………………………………………………….. [2] (b) Two different designs of metal brush are available. One type of brush is made from zinc, while the other type is made from platinum. As the electrolysis takes place, each brush has a different effect on the concentration of zinc ions in the solution. Explain the effect of each type of brush on the concentration of zinc ions in the solution. …………………………...……………………………………………………………….. ………………………………………………...………………………………………….. ………………………………………………………………...………………………….. [3] [Turn over layer of aqueous zinc sulfate

6 A5 Hydrogen peroxide, H2O2, decomposes to give water and oxygen. hydrogen peroxide → water + oxygen A student carried out three experiments to investigate the rate of reaction. He used the same volume and concentration of hydrogen peroxide each time. His first experiment used only hydrogen peroxide. His second and third experiments investigated the effects of adding enzyme A and enzyme B to the reaction mixture. Fig. 5.1 shows the results. Fig. 5.1 (a) (i) Write a chemical equation for the decomposition of hydrogen peroxide. ……………………………………………………………………………..……… [1] (ii) Explain why the decomposition of hydrogen peroxide is also a redox reaction. ……………………………………………………………………………..……… ……………………………………………………………………………..……… ……………………………………………………………………………..……… [2] (b) Suggest a method the student could use to measure the rate of reaction. ……………………………………………………………………………..……………... ……………………………………………………………………………..……………... ……………………………………………………………………………..……………... [2]

7 (c) (i) Describe the effect of each enzyme on the rate of reaction. ……………………………………………………………………..……………... ……………………………………………………………………………………. ……………………………………………………………………..……………... ……………………………………………………………………………………. [2] (ii) Use ideas about activation energy to explain why the shape of the graph is different when no enzyme is used. ……………………………………………………………………………………. ……………………………………………………………………..……………... ……………………………………………………………………………………. [2] (d) The student repeated the same experiment for enzyme B. This time he used the same volume for hydrogen peroxide but at half the original concentration. He continued to measure the volume of gas until the reaction was complete. Sketch a curve on Fig