2024 DHS Y6 H1 Prelim Paper 2 QP

© DHS 2024 8873/02 [Turn over Name: Centre/Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination Year 6 H1 CHEMISTRY Paper 2 Structured Questions Candidates answer on the Question Paper. Additional Materials: Data Booklet 8873/02 11 September 2024 2 hours READ THESE INSTRUCTIONS FIRST Write your centre number, index number, name and class at the top of this page. Write in dark blue or black pen. You may use an 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. Section A Answer all questions. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. A Data Booklet is provided. 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 13 3 17 4 20 Section B 5 / 6 20 Total 80 This document consists of 24 printed pages.

2 © DHS 2024 8873/02 Section A Answer all the questions in the spaces provided. 1 (a) Petrol is a mixture of hydrocarbons that includes octane, C8H18. The density of petrol is typically 748.9 kg per litre and comprises 95% octane by mass. (i) Write an equation for the complete combustion of octane. ……………………………………………………………………………………... [1] (ii) Calculate the volume of carbon dioxide gas that will be emitted at r.t.p., if a full tank carrying 50 litres of petrol is completely combusted. You should assume that only octane undergoes combustion. [3] (iii) Ethanol is sometimes added to the petrol for internal combustion engine. The standard enthalpy change of combustion of ethanol, Hc, can be determined by applying Hess’ Law to the energy cycle in Fig. 1.1. Fig. 1.1 Express the standard enthalpy change of combustion of ethanol, Hc, in terms of x, y and z. ……………………………………………………………………………………... [1] (iv) State the type of enthalpy change that x represents. ……………………………………………………………………………………... [1] 7 2ൗ Hc

3 © DHS 2024 8873/02 [Turn over (b) Exhaust gases from internal combustion engine are harmful to the environment. These include oxides from carbon and nitrogen. (i) Write an equation to show the removal of carbon monoxide and nitrogen monoxide from the exhaust gases. ……………………………………………………………………………………... [1] (ii) State one reason why carbon monoxide is harmful. ………………………………………………………………………………………… ………………………………………………………………………………………… ……………………………………………………………………………...………. [1] (iii) Butane is a fuel that is commonly used in gas canisters that light up stoves. Suggest, with reference to structure and bonding, why butane is used as a fuel in gas canisters but not octane. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ……………………………………………………………………………...………. [2] [Total: 10]

4 © DHS 2024 8873/02 2 (a) Describe and explain the variation in ionic radius across Period 3 of the Periodic Table for the elements Na to Cl. ………………..………………………………………………………………………………… …………………………….…………………………………………………………………… ……………………………………………..…………………………………………………… ………………..………………………………………………………………………………… …………………………….…………………………………………………………………… ……………………………………………..…………………………………………………… ………………………………………………………………….……………………………… ………………..………………………………………………………………………………… …………………………….…………………………………………………………………… ……………………………………………..…………………………………………………… ………………………………………………………………….……………………………… ………………………………..………………………………………………………………… ………………………………..……………………………………………………………. [4] (b) (i) State what is meant by the term electronegativity. …………………………………………………………………………………...…. [1] (ii) State how the bonding in the oxides of the elements sodium to sulfur changes across Period 3. Explain this change in terms of the electronegativities of these elements. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ……………………………………………………………………………...………. [2]

5 © DHS 2024 8873/02 [Turn over (c) Ammonia, NH3, forms ammonium cation, NH4+, when dissolved in water. (i) Draw a ‘dot-and-cross’ diagram to show the bonding in NH4+. [1] (ii) State the shape and bond angle of NH3 and NH4+. Explain your answers using the Valence Shell Electron Pair Repulsion (VSEPR) theory. shape of NH3 ………………….…………… bond angle of NH3 ……….….… shape of NH4+ ………………….………….. bond angle of NH4+ ……………. ……………………………………………………………………………………….… ……………………………………………………………………………………….… ………………………………………………………………………………….……… …………………………………………………………………………………….…… …………………………………………………………………………………….…… …………………………………………………………………………………….…… ………………………………………………………………………………….……… ………………………………………………………………………………….….. [5] [Total: 13]

6 © DHS 2024 8873/02 3 (a) The structure of compound M, C8H15COOH, is shown below. CH2CH CCH2 C C CH2CH3 CH3 OH OH H M (i) Draw the skeletal formula of M. [1] In the liquid state, M forms a dimer, (C8H15COOH)2. (ii) By representing the structure of M as RCOOH, draw a suitable diagram to illustrate the formation of the dimer. Include lone pairs, dipoles and label the interactions formed. [2]

7 © DHS 2024 8873/02 [Turn over (b) Dinitrogen tetroxide, N 2O4, and nitrogen monoxide, NO, can exist in equilibrium with dinitrogen trioxide, N2O3. N2O4(g) + 2NO(g) ⇌ 2N2O3(g) H = −26 kJ mol−1 (i) Write an expression for the equilibrium constant, Kc, including its units. [2] (ii) A mixture containing a 1:2 ratio of N2O4 and NO was allowed to reach equilibrium in a 5 dm3 sealed vessel. At equilibrium, the amount of each compound was determined. compound amount / mol N2O4 0.153 NO 0.307 N2O3 0.0511 Calculate the value for Kc. [1]

8 © DHS 2024 8873/02 (iii) State and explain how the position of equilibrium might change when • temperature is increased, …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… • the vessel is compressed. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2] (iv) Predict how the value of Kc will change when • temperature is increased, …………………………………………………………………………………………… • the vessel is compressed. …………………………………………………………………………………………… [1]

9 © DHS 2024 8873/02 [Turn over (c) The graph shows the results obtained when the rate of thermal decomposition of benzoyl peroxide is investigated. The reaction is first order with respect to benzoyl peroxide. [benzoyl peroxide] × 10−2 / mol dm−3 time/ min (i) Explain in terms of particles why the rate of decomposition decreases with time. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… ……………………………………………….……………………………...…..……. [1] (ii) Use the graph to show that the overall rea