2025 JC2 Prelims H1 Chem Paper 1 QP TJC

1 8873 / TJC Prelims / 2025 TEMASEK JUNIOR COLLEGE 2025 JC2 PRELIMINARY EXAMINATION Higher 1 CHEMISTRY 8873/01 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 13 printed pages and 3 blank pages.

2 8873 / TJC Prelims / 2025 1 An ion, Q has the following properties: • has a noble gas configuration • has more protons than electrons • was obtained by removing electrons from the same orbital Which of the following could be Q? A Al3+ B Ca2+ C Cu2+ D S2– 2 Which ion would undergo the greatest deflection in an electric field? A 4He2+ B 19F− C 14N2+ D 16O22+ 3 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+ 4 Which of the following cannot be explained by hydrogen bonding? A An ice cube floats on water. B The difference in volatility between pentan-1-ol and hexan-1-ol. C The difference in melting point between and . D The higher than expected relative molecular mass of ethanoic acid in benzene.

3 8873 / TJC Prelims / 2025 [Turn over 5 Which one of the following sets of substances includes a giant metallic structure, a giant ionic lattice structure and a simple molecular structure? A Sr, Al2O3, I2 B Be, Al2Cl6, SO3 C Al, C, SiO2 D Ni, PCl3, SiCl4 6 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 7 Which species contain dative (co-ordinate) bonding? 1 CO 2 N2H4 3 Al2Cl6 A 1 and 2 only B 1 and 3 only C 1, 2 and 3 D 3 only

4 8873 / TJC Prelims / 2025 8 The conversion of diamond to graphite is exothermic: C(diamond) → C(graphite) H = −3 kJ mol−1 However, the reaction does not occur. Which statement best explains the above? A A tetrahedral configuration is always more stable than a planar one. B Diamond has only strong covalent bonds whereas graphite has both covalent bonds and instantaneous dipole-induced dipole interactions. C The change from diamond to graphite has a high activation energy. D The bond angle for diamond is smaller than that of graphite. 9 When 10 cm3 of a gaseous hydrocarbon was sparked with 100 cm3 oxygen gas and cooled to room temperature, the gaseous mixture contracted to 80 cm3. When the residual gas was passed through aqueous potassium hydroxide, there was a further contraction of 40 cm3. What is the identity of the hydrocarbon? A 2–methylpropene B propane C butadiene D butane 10 Which species contains a different number of electrons from the other three? A ClO4– B H2SO4 C SO42– D Sn2+

5 8873 / TJC Prelims / 2025 [Turn over 11 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 12 Equations involving three enthalpy changes are shown. Na(g) → Na+(g) + e– ∆H = w Na(g) → Na2+(g) + 2e– ∆H = x Na(s) → Na2+(g) + 2e– ∆H = z Which expression represents the second ionisation energy of sodium? A 2w B x – w C x D z

6 8873 / TJC Prelims / 2025 13 An energy cycle is shown. The standard enthalpy changes involved are X, Y and Z. The numerical value of standard enthalpy change Y and Z are 890 and 964, respectively. Which of the three values are negative? A X and Z only B X only C Y and Z only D Y only 14 The Boltzmann distribution shows the number of molecules having a particular energy at constant temperature. Which of the following statements are correct? 1 The maximum of the curve shifts to the right when the temperature is raised. 2 The Ea decreases when the temperature increases. 3 Lowering the temperature will decrease the total areas labelled L, M and N. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only

7 8873 / TJC Prelims / 2025 [Turn over 15 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 16 Bromine and methanoic acid react as follows Br2(aq) + HCOOH(aq) → 2Br– (aq) + 2H+ (aq) + CO2(g) In one experiment, the concentration of Br2(aq) and HCOOH(aq) used are equal. The rate of reaction is found to be first order with respect to both bromine and to methanoic acid. Which of the following statements about the above reaction is correct? A The units of the rate constant is s–1. B The half-life of the reaction is constant. C The rate of formation of H+(aq) is half the rate of disappearance of Br2(aq). D Doubling the concentration of methanoic acid doubles the rate of evolution of gas.

8 8873 / TJC Prelims / 2025 17 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. 18 Which of the following statements about the properties of Group 1 elements down the group is correct? A The reducing power increases. B The reactivity with water decreases. C The strength of metallic bond increases. D The electronegativity of elements increases.

9 8873 / TJC Prelims / 2025 [Turn over 19 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 20 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 The volatility of the halogen increases down the group. D The thermal stability of the hydrogen halides increases down the group. 21 A 2 dm3 solution was made by mixing 0.0025 mol of HC l(aq) and 0.0040 mol of NaOH(aq). What was the pH of the resulting solution? A 2.82 B 3.13 C 10.9 D 11.2

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