2025 JC2 Prelims H2 Chem Paper 1 QP TJC

1 9729 / TJC Prelims / 2025 TEMASEK JUNIOR COLLEGE 2025 JC2 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9729/01 Paper 1 Multiple Choice 17 September 2025 1 hour Additional Materials: Multiple Choice Answer Sheet (OMS) Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. There are thirty questions In this paper. Answer all questions. For each question there are four possible answers A, B, C, D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer sheet. Read the instructions on the Answer sheet very carefully. Write your name & Civics Group on the Answer sheet. Shade your index number in the appropriate boxes. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. This document consists of 16 printed pages.

2 9729 / TJC Prelims / 2025 1 Which ion would undergo the greatest deflection in an electric field? A 4He2+ B 19F− C 14N2+ D 16O22+ 2 An isolated gaseous species has paired electrons in at least one of its 3d orbitals and a fully filled 4s subshell. What could be the identity of the species? A Cu B Mn C Fe D Fe2+ 3 Which of the following cannot be explained by hydrogen bonding? A The existence of the hydrogen-difluoride anion, HF2–. B The difference in volatility between pentan-1-ol and hexan-1-ol. C The difference in melting point between 2-nitrophenol and 4-nitrophenol. D The higher than expected relative molecular mass of ethanoic acid in benzene. 4 Four substances have the physical properties shown. Which substance exists as a simple molecular solid at room temperature? melting point / C electrical conductivity solubility in water A −7 does not conduct slightly soluble B 46 does not conduct insoluble C 420 conducts insoluble D 782 does not conduct soluble

3 9729 / TJC Prelims / 2025 [Turn over 5 Which species contain dative (co-ordinate) bonding? 1 CO 2 N2H4 3 N2O4 A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 3 only 6 10 cm 3 of a hydrocarbon was mixed with 50 cm 3 of oxygen and combusted completely. After the resulting gas mixture was cooled and passed through aqueous sodium hydroxide, the volume of the residual gas mixture was found to be ¼ the volume of the original gas mixture before combustion. All volumes were measured at room temperature and pressure. What is the formula of the hydrocarbon? A C2H4 B C2H6 C C3H6 D C3H8 7 Which species contains a different number of electrons from the other three? A ClO4– B H2SO4 C SO42– D Sn2+

4 9729 / TJC Prelims / 2025 8 Group 2 carbonates such as calcium carbonate decompose thermally to give the metal oxide and carbon dioxide gas. CaCO3 → CaO + CO2 The numerical values of the enthalpy change of the reaction and activation energy are 178 kJ mol–1 and 356 kJ mol–1, respectively. Which reaction pathway diagram best represents this reaction? A B C D 9 Equations involving four enthalpy changes are shown. Na(g) → Na+(g) + e– ∆H = w Na(g) → Na2+(g) + 2e– ∆H = x Na(s) → Na(g) ∆H = y Na(s) → Na2+(g) + 2e– ∆H = z Which expression represents the second ionisation energy of sodium? A 2w B x – w C y + x – w D z – y

5 9729 / TJC Prelims / 2025 [Turn over 10 Consider the following mechanism. L + M → N fast L + N → P + Q slow N + Q → M + P fast What can be deduced from the mechanism? 1 The unit for the rate constant, k, in the rate equation is mol–1 dm3 s–1. 2 The overall equation is 2L + N → 2P. 3 M is a catalyst and Q is an intermediate. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only 11 The kinetics of a reaction was investigated, and the following results were obtained. 2W + X → Y + 2Z What is the numerical value of the rate constant for this reaction? A 0.213 B 0.320 C 21.3 D 1420 12 When an evacuated tube of volume 400 cm3 is filled with gas at 300 K and 101 kPa, the mass of the tube increases by 0.65 g. What is the identity of the gas? A argon B helium C krypton D neon

6 9729 / TJC Prelims / 2025 13 Equal amounts of H 2(g) and I2(g) are mixed and the composition of the mixture is monitored. A graph of the results is shown below. H2(g) + I2(g) ⇌ 2HI(g) H < 0 The experiment is repeated with a change in condition and the following graph of results is obtained. Which of the following is a possible change made in the second experiment? A A catalyst is used in the second experiment. B H2(g) and I2(g) are mixed in a ratio of 2 : 1 in the second experiment. C The second experiment is conducted at a higher pressure compared to the first experiment. D The second experiment is conducted at a lower temperature compared to the first experiment.

7 9729 / TJC Prelims / 2025 [Turn over 14 X, Y and Z represent elements in the Periodic Table. The first ionisation energy of X is greater than the first ionisation energy of Y. The melting point of Z is higher than that of Y. Which row shows the possible identities of X, Y and Z? X Y Z A N P Al B B Al P C Ga Al P D As P Al 15 Which statement about the halogens or halide ions is correct? A Chloride ions are stronger reducing agents than iodide ions. B Bromine does not oxidise chloride ions when added to sodium chloride solution. C A yellow precipitate that is partially soluble in aqueous ammonia is formed when iodine is added to silver nitrate solution. D A pink solution is obtained when one drop of potassium manganate(VII) is added to aqueous sodium bromide solution. 16 An aqueous solution containing 0.10 mol dm −3 zinc sulfate and 0.10 mol dm −3 of copper(II) sulfate is saturated with hydrogen sulfide, H2S, at 15 C. The concentration of S2−(aq) in the solution is 10−35 mol dm−3. The solubility product, Ksp, of zinc sulfide and copper( II) sulfide at 15 C is given below. Ksp /mol2 dm−6 zinc sulfide 10−24 copper(II) sulfide 10−40 Which statement describes what happens in the solution? A Only zinc sulfide is precipitated. B Only copper(II) sulfide is precipitated. C Copper(II) sulfide is precipitated, followed by zinc sulfide. D More precipitate is observed by lowering the pH of the mixture.

8 9729 / TJC Prelims / 2025 17 The graph below shows the change in pH when an acid is gradually added to 10 cm3 of a base. Which pair of acid and base will give the graph above? A 0.1 mol dm−3 HCl(aq) and 0.1 mol dm−3 NH3(aq) B 0.2 mol dm−3 HCl(aq) and 0.2 mol dm−3 Ba(OH)2(aq) C 0.1 mol dm−3 HCl(aq) and 0.2 mol dm−3 NH3(aq) D 0.1 mol dm−3 CH3CO2H(aq) and 0.2 mol dm−3 NaOH(aq) 18 Water dissociates as shown. H2O ⇌ H+ + OH− H > 0 At 25 C, the concentration of water is given as 55.6 mol dm−3. Which of the following statements are correct? 1 At 25 C, the pKa of water is 14. 2 At 25 C, the value of pH < pKw < pKa of water. 3 At 50 C, the value of pKw is lower than 14. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 3 only

9 9729 / TJC Prelims / 2025 [Turn over 19 Which molecule contains one sp hybridised and two sp3 hybridised carbon atoms? A CH2=C=CHCH3 B CH2=CHCN C HOCH2C≡CH D CH3CH2CH=CHCN 20 The presence of a halogen in an organic compound may be detected by heating the organic compound with ethanolic silver nitrate. The following three compounds are heated with ethanolic silver nitrate. Which of the following shows the correct time taken, from the shortest to the longest, for the compounds to produce a precipitate? A 1 < 2 < 3 B 2 < 1 < 3 C 3 < 2 <