ASRJC 2024 H1Chem Prelim P2 QP

ASRJC JC2 Prelim 2024 8873/H1 [Turn over ANDERSON SERANGOON JUNIOR COLLEGE 2024 JC 2 PRELIMINARY EXAMINATION NAME:______________________________ ( ) CLASS: 24 / ___ CHEMISTRY 8873/02 Higher 1 11 September 2024 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and register number in the spaces provided at the top of this page. Write in dark blue or black pen. You may use a pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all 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. Section A 1 / 10 Section B 7/8 / 20 2 / 11 Paper 1 / 30 3 / 14 Paper 2 / 80 4 /7 Percentage Overall 5 / 7 6 /11 Grade This document consists of 22 printed pages and 2 blank pages.

2 ASRJC JC2 Prelim 2024 8873/H1 Section A Answer all the questions in this section in the spaces provided. 1 (a) Phosphorus, sulfur and chlorine are Period 3 elements of the Periodic Table. Table 1.1 shows some properties of the elements P to Cl. Table 1.1 P S Cl number of electrons in 3p subshell number of unpaired electrons Complete Table 1.1 to show the number of electrons in the 3p subshell and the number of unpaired electrons in an atom of P, S and Cl. [2] (b) Fig. 1.1 shows successive ionisation energies of sulfur, S. Fig. 1.1 (i) Explain the general increase in successive ionisation energies for any atom. ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………………………………………………………………... ……………………………….………………………………………………….[2] 0 5000 10000 15000 20000 25000 30000 Ionisation energy / kJ mol–1 1st 2nd 3rd 4th 5th 6th 7th successive ionisation energies of S

3 ASRJC JC2 Prelim 2024 8873/H1 [Turn over (ii) Complete Fig. 1.1 by plotting approximate values for the 2nd successive ionisation energy and the 6th successive ionisation energy of S. [2] (c) Describe the variation in the electrical conductivity of the elements in the third period, sodium to chlorine. Explain this variation in terms of the structures and bonding of the elements. ………………………………………………...…………………………………………... ………...…………………………………………………………………………………... ………..………………….………………………………………………………………... …………...………………………………………………………………………………... …………...………………………………………………………………………………... ……………………………..……………………………………………………………... ………………………………………………………..…………………………………... ……………………………………………………………..……………………………... …………………………………………………………...………………………………... …………………………………………………………...………………………………... ……………………..……………………………………………………………………... …………………………………………………...………………………………………... ………………………………………………...…………………………………………... …………………………………………………..………………………………………... ……………………………….………………………………………………………….[4] [Total: 10]

4 ASRJC JC2 Prelim 2024 8873/H1 2 (a) When ionic compounds are dissolved in water, the ions form electrostatic attractions with water molecules. These attractions are known as ion –dipole interactions. Enthalpy change of hydration, ∆Hhyd is a measure of the strength of the ion–dipole attraction. The ionic radius of the Group 1 ions affects the strength of the attraction between the Group 1 ions and water molecules. The larger the ionic radius, the weaker the electrostatic forces of attraction between the ion and water molecules. Enthalpy change of hydration, ∆Hhyd is defined as the amount of heat evolved when one mole of free gaseous ions is dissolved in a large amount of water forming a solution at infinite dilution. Na+(g) Na+(aq) (i) Describe and explain how ionic radius varies down Group 1 ions. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………[2] (ii) Hence, state the trend in the magnitude of enthalpy change of hydration, ∆Hhyd, down the Group 1 ions. …………………………………………………………………………………[1] (iii) Suggest an equation to represent the enthalpy change of hydration, ∆Hhyd of sulfide ion, S2–. …………………………………………………………………………………[1] (iv) Sodium nitrate, NaNO3 is soluble in water. Draw the ‘dot-and-cross’ diagram of the nitrate ion. The ion contains nitrogen as the central atom and all atoms have 8 electrons in its outer shell. State the shape and bond angle of the nitrate ion. Shape: ……………………… Bond angle: ……………….. [3]

5 ASRJC JC2 Prelim 2024 8873/H1 [Turn over (b) Table 2.1 shows the boiling point of three fluorine containing compounds. Table 2.1 formula boiling point / °C NaF 1695 HF 19.5 CH3CH2F –37.1 Explain the difference in the boiling points in terms of the structure and type of bonding in the three compounds. …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... ………………………………………………………………………………………...[4] [Total: 11]

6 ASRJC JC2 Prelim 2024 8873/H1 3 (a) Ammonia is manufactured using the Haber process. N2(g) + 3H2(g) 2NH3(g) Table 3.1 shows the number of moles of ammonia at equilibrium at various temperatures at 200 atm. In each case, 1.5 mol of N 2 and 3.0 mol of H2 are mixed in a vessel initially. Table 3.1 Temperature / oC Amount of ammonia at equilibrium / mol 300 1.63 400 1.05 500 0.71 (i) Write the Kc expression for the equilibrium, stating its units. [2] (ii) Calculate the value of Kc at 200 atm and 300 C, given that the volume of the vessel is 3 dm3. [2] (iii) State the Le Chatelier’s Principle. …………………………………………………………………………………………... ………………………………………………………………………………………...[1]

7 ASRJC JC2 Prelim 2024 8873/H1 [Turn over (iv) Using the information in Table 3.1, deduce and explain whether the forward reaction is an endothermic or exothermic reaction. …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... ………………………………………………………………………………………...[2] (v) Name the catalyst used and explain its role in the production of ammonia. …………………………………………………………………………………………... ………………………………………………………………………………………...[2] (b) An unknown alkaline solution with a concentration of 0.010 mol dm–3 is thought to be one of the following solutions. • NaOH • NH3 (Kb = 1.78 x 1