2023 SAJC H2 Chem Prelim P3 (QP)

ST ANDREW’S JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS HIGHER 2 CANDIDATE NAME CLASS 2 2 S CHEMISTRY Paper 3 Free Response Candidates answer on the Question Paper. Additional Materials: Data Booklet 9729/03 14 September 2023 2 hours READ THESE INSTRUCTIONS FIRST Write your name and class on all the work that you hand in. 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. Answer all questions in the spaces provided on the Question Paper. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all questions. Section B Answer one question. A Data Booklet is provided. 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. This document consists of 36 printed pages (including this cover page). For Examiner’s Use Q1 21 Q2 20 Q3 19 Q4 or Q5 20 Total 80

2 Section A Answer all the questions in this section. 1 In the manufacture of tinted glass for chapels, a variety of carbonates including calcium carbonate were smelted together to form the needed colourations. (a) (i) Draw a ‘dot-and-cross’ diagram to show the bonding present within a carbonate ion, CO32−. [1] (ii) State and explain, with reference to the VSEPR theory, the shape of the carbonate ion. [2] (iii) When sodium carbonate was added to water, a weakly alkaline solution is produced. Write an equation for this reaction. [1] ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. …………………………………………………………………………………………………………………..

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4 (b) (i) Write a balanced equation, with state symbols, for the thermal decomposition of calcium carbonate under standard conditions. [1] (ii) Construct a fully labelled energy cycle to show that the standard enthalpy change of formation of carbon dioxide is −399 kJ mol-1. Your cycle should include relevant data from the Data Booklet together with the following data. Standard enthalpy change of atomisation of carbon = +715 kJ mol−1 [2] (iii) The enthalpy changes of formation for these species are shown in the following table. Species CaCO3(s) CaO (s) CO2(g) ΔHf / kJ mol–1 –1207 –635 –399 Using your answer in (b)(i) and (ii), calculate the enthalpy change of decomposition of calcium carbonate. [1] (iv) By considering the entropy, ΔS, and enthalpy, ΔH, changes in the decomposition of calcium carbonate , predict if the reaction is spontaneous at high or low temperature. [2] (v) Using relevant data from the Data Booklet , suggest how the decomposition temperature of nickel carbonate would compare with calcium carbonate. Explain your reasoning. [2] ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. …………………………………………………………………………………………………………………..

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6 (c) The reaction of propanone with iodine can be catalysed by an acid. CH3COCH3 + I2 → CH3COCH2I + HI Sketch a Boltzmann distribution curve for the reaction and use it to explain the effect on the rate of the reaction when the catalyst is removed by adding CaCO3. [3] ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. …………………………………………………………………………………………………………………..

7 [TURN OVER (d) When aqueous Cu2+ and Ni are mixed, an equilibrium is set up. Ni + Cu2+ ⇌ Ni2+ + Cu (i) Draw a fully labelled diagram of the experimental set -up used to measure the standard cell potential for this equilibrium. [2] (ii) Calculate the standard cell potential in (d)(i) and hence calculate the standard free energy change, ΔGo, per mole of Cu formed. [2] (iii) Use the Data Booklet to suggest how the position of equilibrium would change when concentrated NH 3 is added to Ni2+/Ni half cell. Explain your answer and write a balanced equation for this reaction. [2] ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………….. …………………………………………………………………………………………………………