RVHS 2023 Chem Sec 3 Paper 2 QP

River Valley High School Pg 1 of 16 Sec 3 RVIP Chemistry End-of-Year Examination 2023 RIVER VALLEY HIGH SCHOOL SEC 3 END-OF-YEAR EXAMINATION CHEMISTRY PAPER 2 9 OCTOBER 2023 1 HOUR 15 MINUTES NAME CLASS 3 INDEX NO. READ THESE INSTRUCTIONS FIRST DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO. Read these notes carefully. Write your name, class and index number in the spaces at the top of this page. 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. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. *Circle the question you attempted in the table on the right. 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 16. The use of an approved scientific calculator is expected, where appropriate. FOR EXAMINERS’ USE ONLY Section A A1 / 4 A2 / 7 A3 / 11 A4 / 11 A5 / 12 Section B B6 (Either / Or)* / 10 TOTAL Statements Significant Figures Units PAPER 2 (60.4%) / 55 PAPER 1 (39.6%) / 30 / 100% This document consists of 16 printed pages.

River Valley High School Pg 2 of 16 Sec 3 RVIP Chemistry End-of-Year Examination 2023 Section A Answer all questions in this section in the spaces provided. The total mark for this section is 45. A1 Table 1.1 shows some information about particles A to F. Table 1.1 Particle Number of protons Number of neutrons Number of electrons A 13 14 13 B 17 20 18 C 19 20 18 D 29 35 27 E 30 34 30 F 47 61 46 Use the letters A, B, C, D, E and F to answer the following questions. (a) Which two particles are atoms? ………………………………………………………………………..………..……… [1] (b) Which two particles have the same mass number? ………………………………………………………………………..………..……… [1] (c) Which two particles combine to form a white precipitate? ………………………………………………………………………..………..……… [1] (d) Which particle combine with hydroxide ion, OH–, to form a blue precipitate? ………………………………………………………………………..………..……… [1] [Total: 4]

River Valley High School Pg 3 of 16 Sec 3 RVIP Chemistry End-of-Year Examination 2023 A2 Recently, it was reported in the New York Times that in the hottest days of the summer, some airplanes were forced to be grounded by extreme heat as the high temperatures reduced the performance of the airplanes’ engines. When temperature increases, air density decreases . This means that the number of particles per unit volume decreases, which then reduces lift and makes it harder for airplanes to take off. Table 2.1 Box A Box B (a) Using ‘o’ to represent air particles, draw diagrams to show the arrangement of air particles at lower temperature and higher temperature in Box A and Box B respectively in Table 2.1. [2] (b) Use ideas of kinetic particle theory to explain how lower temperatures allow an airplane to take off more easily. ………………………………………………………………………..………..……… ………………………………………………………………………..………..……… …………………………………………………………………………………………. [2] larger lift smaller lift

River Valley High School Pg 4 of 16 Sec 3 RVIP Chemistry End-of-Year Examination 2023 (c) The combustion process in airplanes’ engines produce pollutants such as nitrogen monoxide, NO, gas and nitrogen dioxide, NO2. (i) Complete Fig. 2.2 to show how a pure and dry sample of nitr ogen monoxide gas can be collected from the mixture of pollutants. Fig. 2.2 [2] (ii) Suggest a test to find out if the gas collected is still contaminated with nitrogen dioxide. ………………………………………………………………..………….……… ………………………………………………………………..………….……… [1] [Total: 7] mixture of NO and NO2 gases

River Valley High School Pg 5 of 16 Sec 3 RVIP Chemistry End-of-Year Examination 2023 A3 (a) Nitrogen reacts with hydrogen to form ammonia in the presence of finely divided iron according to the equation shown. N2 + 3H2 ⇌ 2NH3 Fig 3.1 shows the volume of ammonia formed when 300 cm 3 of hydrogen and 200 cm3 of nitrogen were added to the reacting mixture. (i) Draw a dot-and-cross diagram to show the bonding in nitrogen. Show only the valence electrons. [1] (ii) The reaction was first carried out at 200 °C, and repeated at 400 °C. In the boxes provided in Fig 3.1, state the temperature (200 °C or 400 °C) that best corresponds to the shape of each curve. [1] (iii) Calculate the percentage yield of ammonia when the reaction was carried out at 200 atm and 200 °C. [3] (iv) Suggest how the reacting conditions can be changed to increase the percentage yield of the reaction. ………………………………………………………………..………….……… [1] Fig. 3.1

River Valley High School Pg 6 of 16 Sec 3 RVIP Chemistry End-of-Year Examination 2023 (b) Ammonia is widely used to produce fertiliser in agriculture. A common method to produce fertiliser is to react ammonia with sulfuric acid. Construct a chemical equation for the reaction between ammonia and sulfuric acid. ………………………………………………………………..………….…………….. [1] (c) Ammonia gas can also be produced by reacting an oxide of nitrogen with hydrogen. NxOy + excess H2 → xNH3 + yH2O 0.100 mol of the oxide N xOy was mixed with excess hydrogen at room temperature and pressure. Results showed that 4800 cm3 of ammonia and 7.20 g of water was produced at room temperature and pressure. (i) Determine the formula of the oxide of nitrogen. [3] (ii) Hence, state the empirical formula of the oxide of nitrogen. ………………………………………………………………..………….……… [1] [Total: 11]

River Valley High School Pg 7 of 16 Sec 3 RVIP Chemistry End-of-Year Examination 2023 A4 (a) Copper(II) sulfate was titrated against sodium iodide as shown in the equation below. 2CuSO4 + 2NaI → Cu2SO4 + I2 + Product Z (i) At the end of the reaction, the solution appears brown. Explain why. ………………………………………………………………..………….……… [1] (ii) Identify product Z. ………………………………………………………………………..…………. [1] (iii) Complete Table 4.1 to show the oxidation states of copper and iodine in the reactants and products. Table 4.1 element oxidation state in reactant oxidation state in product copper iodine [2] (iv) Which element is reduced in the reaction? Use ideas of electron transfer to explain your answer. ………………………………………………………………..………….……… ………………………………………………………………..………….……… [2] (b) Manganese is a transition element with variable oxidation states. To investigate the variable oxidation states, a student added substance X to a sample of potassium manganate(VII), KMnO4, solution. reaction: MnO4–(aq) step 1 MnO42−(aq) step 2 MnO2 (s) observation: purple solution green solution black solid (i) During the reaction, the solution turned from purple to green, and finally a black suspension was formed. Is manganese oxidised or reduced in step 1 of the reaction? Explain your answer in terms of change in oxidation state. ………………………………………………………………………..…………. ………………………………………………………………………..…………. …………………………………………………………………………………… [2]

River Valley High School Pg 8 of 16 Sec 3 RVIP Chemistry End-of-Year Examination 2023 (ii) The half-equation for the reaction of manganate(VII) ion, MnO42–, to form manganese dioxide, MnO2 is shown. Fill in the blanks to balance the equation. MnO42– + …....…H2O + …....…e– → MnO2 + 4OH– [1] (iii) Suggest why a suspension was observed at the end of step 2. ………………………………………………………………..………….……… [1] (iv) State whether substance X is an oxidising or reducing agent. ………………………………………………………………..………….……… [1] [Total: 11] A5 History of the Singapore C