JPJC 2024 H2 Chemistry Promos P2

 Jurong Pioneer Junior College [Turn Over NAME CLASS 24S JURONG PIONEER JUNIOR COLLEGE JC1 YEAR END EXAMINATION 2024 CHEMISTRY 9729/02 Higher 2 Paper 2 Structured Questions 26 Sept 2024 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 Section A 1 10 2 8 3 10 4 10 5 17 Section B 6 20 Penalty (delete accordingly) Lack 3sf in final answer –1 / NA Missing/wrong units in final ans –1 / NA Bond linkages –1 / NA Total 75 This document consists of 16 printed pages and 0 blank page.

2  Jurong Pioneer Junior College 9729/02/J1 YEAR END EXAM/2024 Section A (55 marks) Answer ALL the questions in the spaces provided. 1 (a) Aluminium fluoride is a solid of high melting point (1270 °C) whereas aluminium chloride sublimes at 178 °C. For Examiner’s Use (i) With reference to structure and bonding, explain why aluminium fluoride has such a high melting point while aluminium chloride sublimes upon heating. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… [2] (ii) Experimental lattice energ y is typically obtained from experimental measurements, such as the Born -Haber cycle, which combines several thermodynamic quantities to compute the lattice energy indirectly. Table 1.1 compound Experimental lattice energy / kJ mol–1 Theoretical lattice energy / kJ mol-1 aluminium oxide –15 000 –15 916 sodium oxide –2478 –2481 Table 1.1 shows the experimental and theoretical lattice energies of aluminium oxide and sodium oxide. Suggest a reason why the experimental lattice energy of aluminium oxide is different from the theoretical value. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… [1]

3  Jurong Pioneer Junior College 9729/02/J1 YEAREND EXAM/2024 [Turn Over (b) 0.457 g sample of gaseous aluminium chloride takes up a volume of 52 cm 3 at a temperature of 100 °C and a pressure of 1.02 x 105 Pa. For Examiner’s Use (i) Show that the Mr of the vapour at this temperature is 267. [1] (ii) Using the information in (b)(i), draw a diagram to illustrate clearly the different types of bonding present in a molecule of aluminium chloride. [2] (iii) Hence, state the shape around each A l atom in the molecule drawn in (b)(ii). …………………………………………………………………………………… [1] (c) Lead white is a white pigment used in old paintings. When exposed to air containing traces of hydrogen sulfide, it darkens due to the formation of black lead(II) sulfide, PbS. To restore the white colour, the painting can be treated with acidified aqueous hydrogen peroxide, H2O2. This oxidises the lead(II) sulfide into lead(II) sulfate. (i) Write an equation for the reaction of lead(II) sulfide with acidified aqueous hydrogen peroxide. …………………………………………………………………………………… [1] (ii) What volume of 0.10 mol dm–3 hydrogen peroxide is required to react with 0.25 g of lead(II) sulfide? [2] [Total: 10]

4  Jurong Pioneer Junior College 9729/02/J1 YEAR END EXAM/2024 2 (a) Phosphorus forms more than one allotrope. For Examiner’s Use (i) Write the full electronic configuration of phosphorus atom. …………………………………………………………………………………… [1] (ii) Explain why the atomic radius of phosphorus is smaller than that of silicon. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… [2] (iii) Explain why the first ionisation energy of sulfur is lower than that of phosphorus. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… [1]

5  Jurong Pioneer Junior College 9729/02/J1 YEAREND EXAM/2024 [Turn Over (b) (i) Nitrogen and phosphorus are in the same group and form similar diatomic structures. The corresponding form of P 2 is not stable under standard conditions. Instead, ‘white’ phosphorus, P4, consists of molecules with a tetrahedral structure as shown. Using the data in Table 2.1 below, calculate the enthalpy change for the conversion of ‘white’ phosphorus to the gaseous diatomic molecule, P2. P4(s) → 2P2(g) Table 2.1 ΔH / kJ mol–1 P–P bond energy 198 P≡P bond energy 485 P4(s) → P4(g) +12 For Examiner’s Use [2] (ii) Carbon readily forms multiple bonds with itself, while silicon does not form these bonds as easily. The first com pound containing a Si=Si double bond was synthesised in 1972. One such compound contains the following percentages by mass. C 41.3 % H 10.3 % Si 48.4 % Find the empirical formula of this compound and draw a possible structure, given that it contains only one Si=Si double bond. [2] [Total: 8]

6  Jurong Pioneer Junior College 9729/02/J1 YEAR END EXAM/2024 3 In heavily polluted air, nitrogen dioxide is often formed, and it appears as a brown haze. Nitrogen dioxide is formed by the following reaction: 2NO(g) + O2(g) → 2NO2(g) For Examiner’s Use (a) The following data were obtained from studies of the reaction between NO and O2 in a vessel at constant temperature. Table 3.1 Experiment No. 1 2 3 Initial partial pressure of NO / atm 0.40 0.40 0.80 Initial partial pressure of O2 / atm 0.60 1.20 1.20 Initial rate of reaction / atm s–1 1.08 2.16 8.64 (i) Use the information given in Table 3.1 to determine the orders of reaction with respect to PNO and 2OP . [2] (ii) Write the rate equation for the reaction. …………………………………………………………………………………… [1] (iii) Using the information in Table 3.1 and your answer in (a)(ii), calculate the value of the rate constant with its units. [2]

7  Jurong Pioneer Junior College 9729/02/J1 YEAREND EXAM/2024 [Turn Over (b) 2NO(g) + O2(g) → 2NO2(g) A two-step mechanism is proposed for this reaction . Part of the mechanism is given below. Step 1: 2NO → N2O2 (fast) Step 2: ……………………………………………………… For Examiner’s Use (i) Draw the dot-and-cross diagram of NO. What feature in the structur e of NO that would suggest that first step in the reaction is the fast step? …………………………………………………………………………………… …………………………………………………………………………………… [2] (ii) Write an equation for step 2 in the mechanism above. [1] (iii) Sketch a reaction pathway diagram for the proposed mechanism represented by steps 1 and 2. Label your diagram with the following:  the activation energy of the rate-determining step;  ΔH of the reaction. [2] [Total: 10]

8  Jurong Pioneer Junior College 9729/02/J1 YEAR END EXAM/2024 4 A goal of chemists is to create a viable process that, like photosynthesis, will convert carbon dioxide into fuel. For Examiner’s Use (a) One of the many developments is to concentrate sunlight onto cerium(IV) oxide catalyst, in contact with carbon dioxide and water, to make ca