RVHS 2026 Prelim P2 QP

RIVER VALLEY HIGH SCHOOL Preliminary Examination CANDIDATE NAME CLASS CENTRE NUMBER S INDEX NUMBER CHEMISTRY 9476/02 Paper 2 Structured Questions 2 hours You must answer on the question paper. You will need: Data booklet INSTRUCTIONS • Answer all questions. • Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. • Write your name, centre number and index number in the boxes at the top of the page. • Write your answer to each question in the space provided. • Do not use an erasable pen. Do not use correction fluid or tape. • You may use an approved calculator. INFORMATION • The total mark for this paper is 75. • The number of marks for each question or part question is shown in brackets [ ]. For Examiner’s Use Question Number 1 2 3 4 5 Marks 17 16 18 11 13 significant figures units Total 75 This document has 28 pages. Any blank pages are indicated. [Turn over

2 River Valley High School 9476/02/Prelims/26 1 In coastal cities, volatile organic compounds (VOCs) released from industrial solvents mix with salty sea spray aerosols. Researchers have isolated a key chlorinated intermediate, compound P, which acts as a precursor to hazardous photochemical smog. (a) To track the decomposition of pollutants like compound P, aerosol samples are subjected to intense heat to liberate their constituent halogen atoms as halide ions. (i) A liquid aerosol sample containing chloride ions is treated with excess aqueous silver nitrate, followed by dilute aqueous ammonia. State the observations and write a balanced ionic equation , with state symbols, for the reaction that occurs upon adding aqueous ammonia. …………………………………………………………………………………………….. ………………………………………………………………………………………..…… …………………………………………………………………………..................... [2] (ii) Sea spray aerosols also carry traces of bromide and iodide ions. When hydrogen halides are regenerated in acidic upper atmospheric clouds, their stabilities vary. Describe and explain the trend in thermal stability of Group 17 hydrides from HCl to HI. Explain your answer with reference to orbital overlap. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… ………………………………………………………………………………………. [2]

3 River Valley High School 9476/02/Prelims/26 [Turn over (b) In humid environments, trapped halogenoalkanes undergo hydrolysis within the aqueous phase of the aerosol. Compound P and two of its structural derivatives, Q and R, are monitored for their relative rates of hydrolysis. Q R Arrange P, Q and R in order of decreasing relative rate of hydrolysis. Explain your answer. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… ………………………………………………………………………………………………. [3]

4 River Valley High School 9476/02/Prelims/26 (c) Following a degradation seq uence, compound P forms an asymmetrical arene intermediate, compound S. Compound S is treated with a dilute solution of chlorine dissolved in an inert solvent at room temperature . Explain why monochlorination occurs selectively on one of the rings. …………………………………………………………………………………………………… …………………………………………………………………………………………………… ………………………………………………………………………………………………. [2]

5 River Valley High School 9476/02/Prelims/26 [Turn over (d) In a laboratory setting, compound P can be synthesised from methoxybenzene. This reaction requires a catalyst and a suitable reagent. You may assume that the OCH3 group is inert. Draw the mechanism for the formation of compound P from methoxybenzene, showing: • the generation of the electrophile • the attack on the aromatic ring • the formation of the substituted product Include all relevant lone pairs, curly arrows and charges. [3]

6 River Valley High School 9476/02/Prelims/26 (e) Unlike aromatic rings, an isolated alkane or aliphatic side chain undergoes a completely different type of halogenation. Compound T reacts with bromine to yield three different mono-bromoalkanes. (i) Name the type of mechanism, and state the reagents and conditions required for this reaction to take place. Type of mechanism: …...…………………………………………………………….…. Reagents and conditions: .………………………………………………................ [2]

7 River Valley High School 9476/02/Prelims/26 [Turn over (ii) Experiments show that during such reactions, hydrogen atoms of the primary, secondary and tertiary carbons are replaced by bromine atoms at different rates, as shown in Table 2.1. Table 1.1 reaction relative rate primary 1 secondary 7 tertiary 21 Using the information in Table 1.1, draw the structures of the three mono-bromoalkanes and predict the relative ratio in which they are formed. [3] [Total: 17]

8 River Valley High School 9476/02/Prelims/26 2 Dextromethorphan is a common over-the-counter cough medicine. dextromethorphan Fig. 2.1 When a dextromethorphan molecule reacts with an acid like hydrobromic acid, HBr , a salt is formed. This salt is known as dextromethorphan hydrobromide monohydrate. (a) In Fig. 2.1, circle the atom that reacts with HBr and name the shape about this atom in the salt produced. ………………………………………………………………………………....................... [2] (b) Explain why , in terms of forces of attraction between particles , the salt product dissolves easily in water. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …...………………………………………………………………………………………….. [2]

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10 River Valley High School 9476/02/Prelims/26 (c) F is a precursor in the synthesis of dextromethorphan. A reaction pathway to produce F is shown in Fig. 2.2. Fig. 2.2 The conversion of A to B involves the use of Grignard reagent which has extensive uses in organic synthesis. An example is shown in Fig. 2.3. R−X RMgX RCOOH + MgXCl Fig. 2.3 (Grignard reagent) Mg 1) CO2 2) HCl(aq)