2024 H1 Chem JC2 Prelim P2 QP JPJC

© Jurong Pioneer Junior College [Turn over Name:____________________________________ Class:_____________ JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2024 CHEMISTRY 8873/02 Higher 1 2024 Paper 2 2 hours Additional materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and exam index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a HB pencil for any diagrams, graphs. Do not use staples, paper clips, glue or correction fluid. Section A (60 marks) Answer all the questions. Section B (20 marks) Answer one question. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 6 2 17 3 6 4 9 5 12 6 5 7 5 Section B 8 20 9 20 Penalty (delete accordingly) Missing/wrong units in final answer –1 / NA Total 80 This document consists of 24 printed pages and 4 blank pages.

2 © Jurong Pioneer Junior College 8873/02/J2 PRELIMINARY EXAMINATION /2024 Section A Answer all the questions in this section, in the spaces provided. 1 The oxygen family is also called the chalcogens. It consists of the elements found in Group 16 of the periodic table, oxygen, sulfur, selenium, tellurium and polonium. Chalcogen can be found in nature in both free and combined states. For Examiner’s Use (a) Complete the diagram to show the arrangement of electrons in the orbitals of a sulfur atom. 1s 2s 2p 3s 3p [1] (b) State and explain the general trend in the first ionisation energy across Period 3 elements. Explain why sulfur does not follow this general trend. ………………………………………………………………………………………..... ………………………………………………………………………………………..... ………………………………………………………………………………………..... ………………………………………………………………………………………..... ………………………………………………………………………………………..... [2] (c) Selenium burns in air with a blue flame to form white solid SeO 2. When SeO2 reacts with water it forms H2SeO3(aq) which has a pH of less than 7. (i) Choose two oxides, each containing a different Period 3 element, which behave in a similar way to SeO2 when they are added to water. Write equation for the reaction of each oxides with water. …………………………………………………………………………………... …………………………………………………………………………………... [2] (ii) Suggest one other reagent that will react with separate samples of these oxides and with SeO2. …………………………………………………………………………………... [1] [Total: 6]

3 © Jurong Pioneer Junior College 8873/02/J2 PRELIMINARY EXAMINATION /2024 [Turn over 2 Nitrogen and phosphorus are elements of Group 15 in the Periodic Table. For Examiner’s Use (a) Nitrogen exists naturally as gaseous diatomic N N molecules whereas phosphorus is a solid and exists as P 4 molecules comprising of P -P single bonds. Account for the difference in their physical states in terms of structure and bonding. ………………………………………………………………………………………..... ………………………………………………………………………………………..... ………………………………………………………………………………………..... ………………………………………………………………………………………..... ………………………………………………………………………………………..... [2] (b) Nitrogen exhibits a range of oxidation numbers in its compounds. (i) Complete the table below which refers to the various oxidation numbers of nitrogen in its compounds. Compound Oxidation Number of Nitrogen NO2 NO3‒ N2O NH2OH Table 2.1 [2] Hydroxylamine, NH2OH is oxidised by Fe 3+(aq), which is itself reduced to Fe2+(aq). In an experiment, 0.0825 g of N H2OH required 20.00 cm 3 of 0.250 mol dm-3 Fe3+ for complete reaction. (ii) How many moles of Fe3+ react with one mole of NH2OH? [2]

4 © Jurong Pioneer Junior College 8873/02/J2 PRELIMINARY EXAMINATION /2024 (iii) What change in oxidation number does the nitrogen in NH 2OH undergo during the reaction with Fe3+? Explain your answer. …………………………………………………………………………………... [1] (iv) Which formula from Table 2.1 corresponds to the nitrogen -containing product of this reaction? ……………………… [1] (v) Construct the half equations and hence the overall balanced equation for the reaction of NH2OH with Fe3+ (in acidic solution). [2] (c) Nitrate, NO 3‒, and phosphate, PO 43‒, are oxoanions of nitrogen and phosphorus respectively. Phosphoric acid , H 3PO4, is used in the production of Coca -Cola and other soft drinks. It serves as an acidulant, providing a tangy flavor and acting as a preservative to maintain the drink's freshness and shelf life. Draw a dot-and-cross diagram to show the bonding PO43‒. [1]

5 © Jurong Pioneer Junior College 8873/02/J2 PRELIMINARY EXAMINATION /2024 [Turn over (d) Phosphoryl chloride is a colourless liquid with the formula POCl₃. Table 2.2 shows the electronegativity values of the atoms in POCl₃. atom electronegativity / pauling units phosphorus 2.2 chlorine 3.0 oxygen 3.5 Table 2.2 (i) Explain the term electronegativity. …………………………………………………………………………………... …………………………………………………………………………………... [1] (ii) Draw the shape of POCl₃. Indicate clearly the polarity of each bond it contains, and its overall net polarity. [2] (iii) Predict all possible intermolecular forces which could exist between POCl₃ molecules. Explain how these forces arise. …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... [3] [Total: 17]

6 © Jurong Pioneer Junior College 8873/02/J2 PRELIMINARY EXAMINATION /2024 3 An experiment was conducted to determine the molar enthalpy change of a reaction, H1. reaction 1 NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g), H1 In this experiment, 5.00 g of sodium hydrogen carbonate was added 50.0 cm 3 of hydrochloric acid in a polystyrene cup at time , t, = 3.0 min. T he temperature of hydrochloric acid was measured at regular time intervals, before and after sodium hydrogencarbonate is added. A graph of temperature, T, against time, t, was obtained as shown in Fig 3.1. For Examiner’s Use (a) Draw a best -fit straight line taking into account all of the points before t = 3.0 min. Draw another best-fit straight line taking into account all of the points after the temperature of the mixture has started to rise steadily. Extrapolate (extend) both lines to t = 3.0 min. Fig. 3.1

7 © Jurong Pioneer Junior College 8873/02/J2 PRELIMINARY EXAMINATION /2024 [Turn over From the graph, read the minimum temperature, Tmin, and the maximum temperature, Tmax, at t = 3.0 min. Deduce the temperature change, T, at t = 3.0 min. Tmin = …………………… Tmax = …………………… T = …………………… [2] (b) Calculate the heat change, q, for your experiment using the value you deduced in (a). Assume that the specific heat capacity of the solution is 4.18 J g –1 K–1 and that the density of the solution is 1.00 g cm–3. [1] (c) Determine the molar en thalpy change, H1, for reaction 1.