2025 SAJC H2 Chem Prelim P1 Questions

1 [Turn Over ST. ANDREW’S JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS HIGHER 2 CANDIDATE NAME CLASS 2 4 S CHEMISTRY Paper 1 Multiple Choice Candidate answer on the Optical Answer Sheet. Additional Materials: Data Booklet 9729/01 18 September 2025 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Optical Answer Sheet. 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 15 printed pages (including this cover page).

2 [Turn Over 1 Which statement is correct? A One mole of a compound is the amount that contains the same number of atoms as there are in 12.0 g of carbon-12. B The relative isotopic mass of beryllium-9 is given by the following expression. average mass of all isotopes of beryllium 1 12 the mass of one atom of C12 C The relative atomic mass of nitrogen is given by the following expression. average mass of one atom of nitrogen 1 12 the mass of one atom of C12 D The relative molecular mass of Q is given by the following expression. average mass of one atom of Q 1 12 the mass of one atom of C12 2 10 cm3 of a gaseous hydrocarbon, CxHy, was exploded with an excess of oxygen. There was a contraction of 40 cm3. When the product s were treated with aqueous sodium hydroxide, there was a further contraction of 50 cm3. All gas volumes were measured at room temperature and pressure. What is the molecular formula of the hydrocarbon? A C4H8 B C4H10 C C5H10 D C5H12 3 In which row are X and Y atoms or ions of different isotopes of the same element? X Y Number of electrons Charge Nucleon number Number of electrons Charge Nucleon number A 3 +3 12 9 –3 12 B 8 0 16 11 –1 19 C 10 +1 23 10 +1 24 D 18 –3 31 12 +3 31 Commented [SXF(1]: Need table outline

3 [Turn Over 4 Which particle will deflect the most when moving with the same speed through an electric field? A Li7 + B B11 3+ C F19 − D P31 3− 5 Which molecules are not polar? 1 H2S 2 CS2 3 SO2 4 SF6 A 1 and 2 B 2 and 4 C 3 and 4 D 4 only 6 A mixture consisting of gaseous compounds, S, T, U and V, is slowly cooled. Gaseous Compound Mr Compound S 72 CH3CH2COCH3 T 74 CH3CH2CH(OH)CH3 U 72 (CH3)4C V 72 CH3CH2CH2CH2CH3 In which order, from first to last, will the compounds condense to form their liquids? A T → S → V → U B U → V → S → T C S → T → V → U D V → U → S → T – Beam of ionic species + Commented [SXF(2]: I added comma

4 [Turn Over 7 Which equation corresponds to the enthalpy change stated? A S8(s) + 12O2(g) → 8SO3(l) ∆HӨformation (SO3(l)) B CaCl2(s) + aq → Ca2+ (g) + 2Cl–(g) ∆HӨsolution (CaCl2(s)) C 2Fe3+(g) + 3O2–(g) → Fe2O3(s) HӨlattice energy (Fe2O3(s)) D H2SO4(aq) + Ca(OH)2(aq) → CaSO4(aq) + 2H2O(l) ∆HӨneutralisation 8 Use of the Data Booklet is relevant to this question. A student mixes 20.0 cm 3 of 5.00 mol dm –3 sulfuric acid with an equal volume of 6.00 mol dm –3 sodium hydroxide. The initial temperature of both solutions is 25.0 °C. The maximum temperature reached after the reaction is 55.0 °C. Assume the density of both solutions is 1 g cm–3. What is the value of the enthalpy change of neutralisation, in kJ mol−1, calculated using these values? A –41.8 B –50.2 C –83.6 D –100.3 9 The half -life of the first -order gaseo us reaction in which M 2 molecules become converted into M atoms is 40 minutes. 1 mol of M 2 is put into a sealed vessel at pressure p. What will be true when 87.5% of M2 has been converted into M atoms? 1 80 minutes have elapsed. 2 1.5 mol of M have been formed. 3 The total pressure is 15 8 p (at constant pressure). A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 3 only Commented [SXF(3]: Which equation corresponds to Commented [SXF(4]: Aligment Commented [SXF(5]: Neutralisation and I included the units cos the A level qns has the units in the opions

5 [Turn Over 10 Curves 1 and 2 show the Boltzmann distributions for identical compositions of a reaction mixture which occur at different temperatures. Which statement is correct? A Curve 1 applies to the faster reaction and point W indicates particles with lower energy than point Z. B Curve 1 applies to the faster reaction and point W indicates particles with higher energy than point Z. C Curve 2 applies to the faster reaction and point X indicates particles with lower energy than point Y. D Curve 2 applies to the faster reaction and point X indicates particles with higher energy than point Y.

6 [Turn Over 11 The graph shows how the initial rate of reaction varies for an enzyme catalysed reaction as the substrate concentration changes. Which of the statements correctly describe the situation when [substrate] = x? 1 The initial rate of reaction is affected by increasing [substrate]. 2 The order of reaction with respect to [substrate] is 1. 3 There are no more enzyme active sites available. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 3 only 12 A sample of 1 mol of XY was placed in an empty 1 dm3 container and allowed to reach equilibrium with a total pressure, p, according to the following equation. 2XY(g) X2(g) + Y2(g) At equilibrium, x mol of XY had dissociated. What is the value of the equilibrium constant, Kp , at the temperature of the experiment? A 𝑥2 (1 − 𝑥)2 B (1 − 𝑥)2 𝑥2 C 4(1 − 𝑥)2 𝑥2 D 𝑥2 4(1 − 𝑥)2 x Initial rate [substrate]

7 [Turn Over 13 Orange dichromate( VI), Cr 2O72–, and yellow chromate( VI) ions, CrO 42–, exist in equilibrium in aqueous solution. Cr2O72–(aq) + H2O(l) 2CrO42–(aq) + 2H+(aq) Which statement about this equilibrium is correct? A Lowering the pH will increase concentration of CrO42– ions. B Addition of a catalyst will shift the position of equilibrium to the left. C Addition of water will shift the position of equilibrium to the left. D In strong alkali, the solution appears yellow. 14 The table shows the fifth ionisation energies of four consecutive elements in the Periodic Table. Element E F G H Fifth IE / kJmol–1 37832 9445 10989 13327 What is the formula of the chloride of E? A ECl2 B ECl3 C ECl4 D ECl5 15 Which pair contains an Arrhenius acid and Arrhenius base? Acid Base A KCl NaOH B HCl KOH C CH3COOH NH3 D H2SO4 NH3 Commented [NHs(6]: Changed this from full stop to question mark

8 [Turn Over 16 An excess of silver bromide is added to water and the mixture is shaken until equilibrium is reached. How is the solubility of silver bromide, in this equilibrium mixture, affected by the addition of either • aqueous ammonia or • aqueous potassium bromide? addition of aqueous ammonia addition of aqueous potassium bromide A decreases decreases B decreases increases C increases increases D increases decreases 17 Brassicasterol is a plant sterol found in sources like rapeseed oil and marine algae. OH brassicasterol How many stereoisomers does brassicasterol have? A 29 B 210 C 211 D 212

9 [Turn Over 18 In the free radical substitution of 2 -methylbutane with chlorine, a mixture of mono-chlorinated compounds was obtained. Assuming the rate of reaction at all the carbon atoms are the same, which statements are correct? 1 The ratio for the two compounds with the highest yields is 2:1. 2 Homolyt