RVHS Prelim H1 Chemistry P2 QP

River Valley High School 8873/02/PRELIMS/25 [Turn over 2025 JC 2 Preliminary Examination RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATIONS CANDIDATE NAME CLASS 2 4 J INDEX NUMBER H1 CHEMISTRY 8873/02 Paper 2 Structured Questions 16 September 2025 2 Hours Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST. DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO. Write your name, class and index number in the spaces 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, highlighters, glue or correction fluid. Section A Answer all questions in the spaces provided on the Question Paper. The question number must be clearly shown. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. This paper consists of 24 printed pages. For Examiner’s Use Paper 1 30 Paper 2 1 11 2 8 3 6 4 10 5 7 6 10 7 8 8 20 9 20 s.f. units Paper 2 80 Total 110

2 River Valley High School 8873/02/PRELIMS/25 2025 JC 2 Preliminary Examination Section A Answer all the questions in this section in the spaces provided. 1 Iron ore deposits are found globally, with significant reserves in Australia, Brazil, Russia, China, and India. A company refining iron ore would only purchase more ores from distributors if the percentage of iron in each ore is >60%. If it is any lower than this, then the cost of refining the ore will be considered expensive. (a) Define the term mole. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. [1] (b) An experiment was carried out to determine the percentage of iron in a sample of iron ore. A 3.35 g piece of ore was reacted with dilute sulfuric acid, in the absence of air, so that all the iron atoms were converted to iron(II) ions. The resulting solution was made up to 250 cm3. Other substances in the ore do not react and are filtered out of the mixture. A 25.0 cm 3 sample of this iron(II) solution was further acidified with 10.0 cm3 of sulfuric acid and titrated with 0.0250 mol dm−3 purple potassium manganate(VII). 32.00 cm3 of the potassium manganate(VII) solution was required for complete reaction. The relevant half-equations for the reaction are shown below. MnO4– + 8H+ + 5e– → Mn2+ + 4H2O Fe3+ + e– → Fe2+ (i) Write a balanced equation for the reaction between the iron in the ore and the sulfuric acid. ……………………………………………………………………………… [1] (ii) State the role of potassium manganate(VII) in the reaction with the iron(II) solution. Explain your answer in terms of oxidation number. ……………………………………………………………………………… ……………………………………………………………………………… [2] (iii) Given that Fe3+(aq) is yellow in colour, determine the colour change at the end point in this titration. ……………………………………………………………………………… [1]

3 River Valley High School 8873/02/PRELIMS/25 [Turn over 2025 JC 2 Preliminary Examination (iv) Using the two half-equations, construct an overall equation for the reaction between manganate(VII) ions and iron(II) ions in acid ic solution. ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… [1] (v) Calculate the amount of manganate(VII) ions used in the titration. [1] (vi) Calculate the total amount of iron(II) ions in 250 cm3 of the solution. [1] (vii) Hence, calculate the percentage by mass of iron in the 3.35 g piece of ore. If you were unable to obtain a value in (b)(vi), use the value of 3.00  10−2 mol. This is not the correct answer. State whether ores can be purchased from this distributor. [3] [Total: 11]

4 River Valley High School 8873/02/PRELIMS/25 2025 JC 2 Preliminary Examination 2 In water treatment, ammonia reacts with hypochlorous acid to form monochloramine, a long-lasting disinfectant that produces fewer harmful by-products. HOCl + NH3 → NH2Cl + H2O (a) (i) Given that O and N are the central atoms in HOCl and NH2Cl, respectively, draw the ‘dot-and-cross’ diagrams for HOCl and NH2Cl. [2] (ii) Explain the differences in shape and bond angles of HOCl and NH2Cl using the Valence Shell Electron Pair Repulsion (VSEPR) theory. ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… [3] (iii) Deduce whether HOCl is a polar molecule. Explain your answer. ……………………………………………………………………………….. ……………………………………………………………………………….. [1] (b) Explain, in terms of structure and bonding, whether HOCl or CsCl has a higher boiling point. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [2] [Total: 8]

5 River Valley High School 8873/02/PRELIMS/25 [Turn over 2025 JC 2 Preliminary Examination 3 Benzylacetamide can be formed from benzyl alcohol via a three-step synthesis. (a) Draw the structures of Intermediate 1 and Intermediate 2. [2] Intermediate 1 Intermediate 2 (b) State the reagents and conditions required for each of the three steps. Step 1: ……………………………………………………….............................. Step 2: ……………………………………………………….............................. Step 3: ……………………………………………………….............................. [3] (c) Draw the structure formed when benzyl alcohol and phenylacetic acid are heated in the presence of a few drops of concentrated sulfuric acid. [1] [Total: 6]

6 River Valley High School 8873/02/PRELIMS/25 2025 JC 2 Preliminary Examination 4 An experiment is performed to determine the maximum change in temperature for the following reaction: Mg(s) + CuSO4(aq) → Cu(s) + MgSO4(aq) 25.0 cm3 of 1.00 mol dm−3 CuSO4(aq) is transferred to a polystyrene cup. The initial temperature of CuSO4(aq) is 25.0 ºC. The temperature of CuSO4(aq) is recorded every 0.5 minute for 2.5 minutes before 1.00 g of Mg is added into the polystyrene cup at exactly 3.0 minutes. The mixture is stirred thoroughly, and temperature is continuously recorded every 0.5 minute from 3.5 minutes to 9.0 minutes. The results are shown in Fig. 4.1. Fig. 4.1 Time / min Temperature /oC

7 River Valley High School 8873/02/PRELIMS/25 [Turn over 2025 JC 2 Preliminary Examination (a) (i) Draw two separate straight lines of best fit. The first line should take into account all the points before 3.0 minutes. The second line should take into account all of the points after the temperature of the mixture starts to fall steadily. Extrapolate both lines to 3.0 minutes. Use your graph to estimate the maximum temperature of the mixture at 3.0 minutes. Show your working. Maximum temperature = _______________ [2] (ii) Using the value in (a)(i), determine the maximum temperature rise produced by the reaction. [1] (iii) With reference to Data Booklet and u sing your answer in (a)(ii), calculate the energy, in kJ, evolved during the reaction. [1] (iv) Using your answer to (a)(iii), calculate a value for the enthalpy change of reaction, in kJ mol ⁻¹, between Mg(s) and CuSO 4(aq) adjusted by cooling curve correction. If you were unable to obtain a value in (a)(iii), use the value of 3.00 kJ. This is not the correct answer. [2]

8 River Valley High School 8873/02/PRELIMS/25 2025 JC 2 Preliminary Examinat