RVHS Prelim H2 Chemistry P3 QP

River Valley High School 9729/03/PRELIMS/25 2025 Preliminary Examination [Turn over RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS 2 4 J CENTRE NUMBER S INDEX NUMBER H2 CHEMISTRY 9729/03 Paper 3 Free Response 23 September 2025 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Centre number, index number, class and name on all the work that you hand in. 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. DO NOT WRITE IN ANY BARCODES. 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 the questions. Section B Answer one question. Circle the question number of the question you attempted. 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. For Examiner’s Use Question Number 1 2 3 4 5 units s.f. Total Marks 21 18 21 20 20 80 This document consists of 31 printed pages and 1 blank page.

2 River Valley High School 9729/03/PRELIMS/25 2025 Preliminary Examination Section A Answer all the questions in this section. 1 Benzene undergoes many different types of reactions to form its derivatives. One such example is the Gattermann–Koch reaction. (a) The chlorides of the elements, sodium to phosphorus, dissolve or react with water. Describe the reactions when excess water is added to separate samples of MgCl2 and PCl5. Write equations for all reactions that occur and suggest the pH of the resulting solutions. [4] ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... (b) Describe and explain the variation in thermal stability of HCl, HBr and HI. [3] ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…...

3 River Valley High School 9729/03/PRELIMS/25 2025 Preliminary Examination [Turn over (c) Explain why benzene undergoes substitution reactions rather than addition reactions. [1] ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... (d) In the Gattermann–Koch reaction, benzene is used to produce benzaldehyde. An example is provided below in Fig. 1.1. Fig. 1.1 The mechanism of this reaction occurs in 2 steps. Step 1: Generation of electrophile, HCO+ Step 2: Reaction of benzene with electrophile, HCO+, to obtain benzaldehyde (i) Define the term electrophile. [1] (ii) In Step 1, CO reacts with HCl in the presence of AlCl3 to form HCO+. HCl + CO → HCO+ + Cl− AlCl3 + Cl− → [AlCl4]− State the roles of CO and AlCl3 respectively in Step 1. [2] (iii) Name and draw the mechanism in Step 2. Use the displayed formula of HCO+, and show relevant curly arrows, charges and the structure of the intermediate. [3] (iv) The synthesis of compound Z shown in Fig. 1.2 involves the Gattermann-Koch reaction. Fig. 1.2 State the reagents and conditions required of Step 1 and Step 3 in Fig. 1.2. Draw the structures of X and Y. [4]

4 River Valley High School 9729/03/PRELIMS/25 2025 Preliminary Examination ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…...

5 River Valley High School 9729/03/PRELIMS/25 2025 Preliminary Examination [Turn over (e) Three organobromine compounds, A, B and C are shown below. A B C Arrange A, B and C in order of decreasing ease of hydrolysis. Explain your answer. [3] ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... [Total: 21]

6 River Valley High School 9729/03/PRELIMS/25 2025 Preliminary Examination 2 An organic compound, C 4H6O2, known as MMA, is the precursor to a thermoplastic known as PMMA. • On treatment with hot acidic KMnO4(aq), MMA produces only 1 organic product, F, with a loss of 1 C atom. • The same compound F is also produced as one of the products when G, C6H8O2, a sweet-smelling compound, is treated with hot acidic KMnO4(aq). • On warming with I2(aq) in the presence of NaOH(aq), F gives a yellow ppt and a sodium salt of H. • 1 mole of H, Mr = 90.0, reacts with excess Na(s) to give 22.7 dm3 of hydrogen gas under standard temperature and pressure. (a) Suggest structures for MMA, F, G and H. Explain the reactions. [8] ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... ……………………………………………………………………………………......…... …………………………………………………………………