VJC 2025 H1ChemistryPrelimP2 QP

© VJC 2025 8873/02/PRELIM/25 [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 1 ……………………………………………….………….. …………………………….. CHEMISTRY 8873/02 Paper 2 Structured Questions Candidates answer on the Question Paper. 29 August 2025 2 hours Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Name and CT group in the spaces at the top of this page. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all the questions. Section B 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 / 11 2 / 20 3 / 9 4 / 7 5 / 13 Section B 6 / 7 / 20 Total / 80 This document consists of 19 printed pages and 1 blank page.

2 © VJC 2025 8873/02/PRELIM/25 Section A Answer all questions from this section in the spaces provided. 1 (a) The element sodium can exist as a number of isotopes. Complete the Table 1.1 for two isotopes species of sodium. Table 1.1 Isotopic species protons neutrons electrons electronic configuration 23 11Na 11 1s2 ……………………… 13 10 1s2 ……………………… [4] (b) Sodium oxide, Na2O and sodium peroxide, Na2O2 are two compounds that can be produced when sodium metal is heated in oxygen under suitable conditions. Both Na2O and Na2O2 are ionic compounds. Each compound contains only one single anion and the charge on each anion is the same. (i) Write the formulae of the anions in Na2O and Na2O2. ………………………………………………………………………………………………. [1] (ii) Draw a ‘dot-and-cross’ diagram of the anion in Na2O2, showing the outer shell electrons only. [1] (iii) Predict the relative magnitudes of the melting points of Na 2O and Na 2O2. Explain your answer. ………..…….…………………………………………………………………………………….. ………..…….…………………………………………………………………………………….. ………..…….…………………………………………………………………………………….. ………..…….…………………………………………………………………………………….. ………..…….…………………………………………………………………………………….. ………………………………………………………………………………………………. [2]

3 © VJC 2025 8873/02/PRELIM/25 [Turn over (c) (i) When the Group 1 cation, M+, is passed through an electric field, it is deflected through an angle of +5.0. The angle of deflection is dependent on the relative masses and charge of the particles as shown. Angle of deflection ∝ charge mass Given that the same electric field deflected 92Sr3+ through an angle of +22, calculate the relative atomic mass (Ar) of M. Hence suggest a possible identity of the M. [2] (ii) Explain why the second ionisation energy of M is more endothermic than its first ionisation energy. ………..…….…………………………………………………………………………………….. ………..…….…………………………………………………………………………………….. ………………………………………………………………………………………………. [1] [Total:11]

4 © VJC 2025 8873/02/PRELIM/25 2 Nitrogen is a vital element for sustaining life on Earth. Despite its high abundance in the atmosphere, the availability of reactive nitrogen compounds for biological and industrial use was historically limited. The development of the Haber process for the synthesis of ammonia, followed by the Ostwald process for the large-scale production of nitric acid from ammonia, in the early 20th century marked a significant breakthrough in expanding the availability of reactive nitrogen species for agricultural and industrial applications. (a) Ammonia is manufactured from nitrogen and hydrogen by the Haber process as shown in the equation: N2(g) + 3H2(g) 2NH3(g) Hrxn = –92 kJ mol–1 Under certain conditions, the system reached dynamic equilibrium with the following gas concentrations. gas concentration/ mol dm−3 nitrogen 1.36 hydrogen 1.84 ammonia 0.142 (i) Explain what is meant by dynamic equilibrium. ……………………………………………………………………………………………………. ……………………………………………………………………………………………... [1] (ii) Write an expression for the equilibrium constant, Kc, for the Haber process. ……………………………………………………………………………………………... [1] (iii) Calculate the value of Kc given the following equilibrium concentrations and state the units of Kc. [2]

5 © VJC 2025 8873/02/PRELIM/25 [Turn over (iv) Suggest a reason why the activation energy for the Haber process is high. ……………………………………………………………………………………………………. ……………………………………………………………………………………………... [1] (v) Describe and explain the conditions required for the favourable production of ammonia in Haber process. ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ……………………………………………………………………………………………... [3]

6 © VJC 2025 8873/02/PRELIM/25 (b) A large proportion of the ammonia manufactured is then used to manufacture nitric acid, which is another industrially important compound. In the chemical industry, synthesis of nitric acid (HNO3) is commonly carried out via the Ostwald process. The first stage in the process involves the catalytic oxidation of ammonia to nitric oxide (NO): 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g) ∆H = –905 kJ mol–1 (i) Explain, in terms of bonds, why the enthalpy change of the reaction is exothermic. ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ……………………………………………………………………………………………... [1] (ii) Using relevant bond energies in the Data Booklet and the given value of enthalpy change for the reaction, determine the N=O bond energy in nitric oxide. [3] (iii) Explain, in terms of frequency of collisions, the effect of increasing the concentration of the reactants on the rate of oxidation of ammonia. ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ………..…………………………………………………………………………………………... ……………………………………………………………………………………………... [2]

7 © VJC 2025 8873/02/PRELIM/25 [Turn over (c) A student investigated the reaction between hydrogen gas and nitric oxide. 2H2(g) + 2NO(g) → 2H2O(g) + N2(g) The following data were obtained. experiment initial concentration of H2(g)/ mol dm–3 initial concentration of NO(g)/ mol dm–3 initial rate/ mo