2022 JPJC Prelim P2 Question Paper

© Jurong Pioneer Junior College [Turn Over NAME CLASS 21S JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2022 CHEMISTRY 9729/02 Higher 2 Paper 2 Structured Questions 14 September 2022 2 hours Candidates answer on the Question Paper. 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. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 10 2 10 3 17 4 10 5 11 6 12 7 5 Penalty (delete accordingly) Bond linkages –1 / NA Significant figures & units –1 / NA Total 75 This document consists of 21 printed pages inclusive of 1 blank page.

2 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2022 Answer all the questions in this section. 1 (a) Figure 1.1 shows the third ionisation energies of eight consecutive elements A to H, in the Periodic Table. [Note that letters A to H are not the atomic symbols of the elements concerned.] Figure 1.1 For Examiner’s Use (i) Write an equation, including state symbols, to represent the third ionisation energy of element A. ………………………………………………………………………………… ………………………………………………………………………………… [1] (ii) From Figure 1.1, suggest the identity of B. Explain how you arrived at your answer. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] (iii) Explain why the third ionisation energy of element D is slightly lower than that of element C. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1] Third Ionisation energy/ kJ mol−1

3 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2022 [Turn Over (b) Nitrogen and phosphorus are elements of Group 15 in the Periodic Table. 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. For Examiner’s Use (i) Account for the difference in their physical states in terms of structure and bonding. ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… [2] (ii) Suggest why phosphorus does not occur naturally as PP molecules. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1] (iii) Nitrate, NO 3‒, and phosphate, PO 43‒, are oxoanions of nitrogen and phosphorus respectively. Draw a dot-and-cross diagram to show the bonding PO43‒, deducing the shape and the bond angle around the phosphorous atom. Hence explain why it is not possible for nitrogen to form an oxoanion with formula of NO43‒. [3] [Total: 10]

4 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2022 2 Iron oxides are chemical compounds composed of iron and oxygen. Most iron ores are oxides, making them important precursors to iron metal and its many alloys. For Examiner’s Use (a) Iron (II) compounds are only stable in neutral, non-oxidising conditions. It is difficult to determine the lattice energy of FeO experimentally. (i) Given the following data in Table 2.1 and data from the Data Booklet, draw and complete the energy diagram below to calculate the lattice energy of FeO(s) in kJ mol−1. standard enthalpy change of atomisation of Fe(s) +416 kJ mol–1 standard enthalpy change of formation of FeO(s) –272 kJ mol–1 Sum of 1st and 2nd electron affinity of oxygen +157 kJ mol–1 Table 2.1 [3] 0 Enthalpy Fe (s) + ½O2 (g)

5 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2022 [Turn Over (ii) Most naturally occurring samples of iron( II) oxides are found as the mineral WÜstite. WÜstite has the formula Fe20Ox. It contains both Fe2+ and Fe3+ ions. 90% of the iron is present as Fe2+ and the remaining as Fe3+. By means of calculations, deduce the value of x. For Examiner’s Use [1] (iii) State and explain how the lattice energy of FeO compares with the lattice energy of Fe2O3. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] (b) Another common iron oxide as hematite, Fe2O3 is the main source of iron for the steel industry. Fe2O3 will readily react with acids to form soluble salts such as the following reaction. Fe2O3(s) + 6HI(aq)→ 2FeI2(aq) + I2(aq) + 3H2O(l) (i) Define standard enthalpy change of solution. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [1]

6 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2022 (ii) Use the data in Table 2.2 to calculate the enthalpy change of solution of iron (II) iodide, FeI2. ∆Hlatt (FeI2(s)) ‒ 2440 kJ mol‒1 ∆Hhyd (Fe2+ (g)) ‒ 1950 kJ mol‒1 ∆Hhyd (I‒ (g)) ‒ 308 kJ mol‒1 Table 2.2 For Examiner’s Use [1] (iii) A yellow precipitate of Pb I2 forms when 25 cm 3 of x mol dm-3 Pb2+ ions are added to 10 cm3 of 0.100 moldm-3 FeI2 (aq). Given that the solubility product, Ksp, of PbI2 = 9.8 x 10 -9 mol3 dm-9, find the minimium value for x, concentration of Pb2+ for precipitation to occur. [2] [Total: 10]

7 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2022 [Turn Over 3 Carboxylic acids and their derivatives are classes of organic compounds that play important roles in our everyday lives. Some of their uses include the manufacturing of polymers, production of pharmaceutical drugs, as food additives and industrial solvents. This question deals with some of the properties of acidic organic compounds, including carboxylic acids and their derivatives. For Examiner’s Use (a) Table 3.1 below shows three organic compounds that can be found in nature. name 1-naphthol hydrocinnamic acid cinnamic acid where it can be found selaginella sinensis tree cowberries cinnamon structural formula OH O OH OH O pKa 9.51 4.70 4.37 Table 3.1 (i) By reference to the structures, explain why cinnamic acid will be the first to react when aqueous KOH is added dropwise to a mixture containing both cinnamic acid and hydrocinnamic acid. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [2] (ii) With the aid of balanced equation(s), explain any reaction(s) that occurs when a solution containing sodium 1-naphtholate is added to a solution containing hydrocinnamic acid. O - Na + sodium 1-naphtholate