HCI 2021 Prelim Paper 1 Questions

This document consists of 14 printed pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 20S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 9729/01 17 September 2021 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Complete the information on the Answer Sheet as shown below. 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 Answer Sheet. Read the instructions on the Answer Sheet very carefully. 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.

© Hwa Chong Institution 2021 9729 / 01 / C2 Prelim 2021 2 1 The successive ionisation energies of the gaseous ion, G+, are given in the table below: number of electrons removed 1 2 3 4 5 6 ionisation energy/ kJ mol –1 1907 2914 4964 6274 21 267 25 431 Which group in the periodic table does G belong to? A 14 B 15 C 16 D 17 2 In which of the following pairs of compounds would the second compound have a higher boiling point than the first compound? 1 HCHO, CH3OH 2 BF3 , AlF3 3 CH3CH2CH2CH2CH3, C(CH3)4 A 1 and 2 B 1 and 3 C 2 and 3 D 1, 2 and 3 3 Information about the properties of some compounds are given below. density / g cm−3 ice 0.931 water 0.997 boiling point / °C HF 19.5 NH3 −33.3 2-nitrophenol 216 4-nitrophenol 279 Which statement about the hydrogen bonding in these compunds is incorrect? A HF has a higher boiling point than NH3 because each HF molecule can form more hydrogen bonds on average compared to each NH3 molecule. B Hydrogen bonds between molecules of H2O in ice causes the density of ice to be lower than that of water. C When CH3CO2H is dissolved in benzene, hydrogen bonding between two molecules of CH3CO2H causes the Mr to double from 60 to 120. D The boiling point of 2-nitrophenol is lower than 4-nitrophenol due to the presence of intramolecular hydrogen bonding in 2-nitrophenol.

© Hwa Chong Institution 2021 9729 / 01 / C2 Prelim 2021 3 4 Which graph will not have the same shape for a fixed mass of gas compared to the rest? (All values are measured in SI units.) A pV against T C pV against V at constant T B p against density at constant T D p against 1/V at constant T 5 When a liquid hydrocarbon was burnt in 100 cm3 of excess oxygen gas, the gaseous mixture contracted by 15 cm3. On passing the resultant gaseous mixture through aqueous sodium hydroxide, there was a further contraction of 60 cm3. What could be the molecular formula of the hydrocarbon? All volumes were measured at room temperature and pressure. A C6H8 B C6H12 C C8H8 D C8H12 6 The main isotopes of sulfur are summarised in the table below: isotope 32S 33S 34S 36S abundance 94.99 0.75 4.25 0.01 Which statements are correct? 1 The relative atomic mass of sulfur is 32.0929. 2 The relative isotopic mass of 33S is the mass of 1 atom of 33S relative to 1 12 of the mass of a 12C atom. 3 When unipositively charged ions of the isotopes of sulfur are passed through an electric field, the angle of deflection for 32S+ ion is the largest. A 1 and 2 B 1 and 3 C 2 and 3 D 1, 2 and 3 7 When 13.1 g of zinc dust was added to 150 cm3 of 1.0 mol dm3 aqueous copper(II) sulfate, the temperature of the solution rose by 15 °C. What is the enthalpy change for the reaction: Cu2+(aq) + Zn(s) o Zn2+(aq) + Cu(s)? Assume the specific heat capacity of the solution is 4.20 J g1 K1 and the density of all solutions is 1.00 g cm−3. A – 47.2 kJ mol1 C – 68.5 kJ mol1 B – 63.0 kJ mol1 D – 1210 kJ mol1

© Hwa Chong Institution 2021 9729 / 01 / C2 Prelim 2021 4 8 Consider the following reactions: 2NaOH(aq) + H2SO4(aq) o Na2SO4(aq) + 2H2O(l) 'H1 NaOH(aq) + CH3CO2H(aq) o CH3CO2Na(aq) + H2O(l) 'H2 Which statements are correct? 1 'H1 represents the enthalpy change of neutralisation. 2 The pH of a solution of CH3CO2Na is greater than 7. 3 The magnitude of 'H1 is twice that of 'H2. A 1 and 3 B 3 only C 2 only D 1, 2 and 3 9 The equation for the reaction between bromate and bromide ions is shown below. BrO3–(aq) + 5Br–(aq) + 6H+(aq) o 3Br2(aq) + H2O(l) From initial rates experiments, the following rate equation was derived. rate = k[BrO3–][Br–][H+]2 The results of the initial rate experiments are shown. initial [BrO3–] / mol dm–3 initial [Br–] / mol dm–3 initial [H+] / mol dm–3 initial rate, 1/t / s–1 0.004 0.04 0.40 0.10 0.004 0.04 0.80 x 0.004 0.08 0.40 y 0.008 z 0.80 1.60 What are the missing values, x, y, and z? x y z A 0.20 0.10 0.08 B 0.20 0.10 0.16 C 0.40 0.20 0.16 D 0.40 0.20 0.08

© Hwa Chong Institution 2021 9729 / 01 / C2 Prelim 2021 5 10 The mechanism for a given gaseous phase reaction is shown below. 2A o C fast C + B o D slow D + B o E fast Which statements are correct? 1 The overall equation is 2A + 2B o E. 2 The units of the rate constant is atm–2 s–1. 3 The initial rate of formation of E is directly proportional to the square of the initial partial pressure of A. A 1 and 2 B 1 and 3 C 2 and 3 D 1, 2 and 3 11 What is the effect on decreasing temperature on the rate constants, kf for the forward reaction and kb for the backward reaction, and on the equilibrium constant Kc, for a reversible reaction where the forward reaction is exothermic? kf kb Kc A decrease decrease increase B decrease decrease no effect C increase decrease increase D increase increase decrease

© Hwa Chong Institution 2021 9729 / 01 / C2 Prelim 2021 6 12 When an acid is titrated with a strong base, the equivalence point is reached when the amount of base added is equal to the amount of H+ dissociated. Sulfurous acid, H2SO3, a dibasic acid, has pKa values of 1.9 and 7.1. The curve for the titration of 25.0 cm3 of 0.10 mol dm–3 sulfurous acid against a standard solution of sodium hydroxide, NaOH, is shown below. The pH ranges of colour changes for thymol blue indicator are 1.2 – 2.8 and 8.0 – 9.6. Which statement is correct? A The initial pH of 0.10 mol dm–3 sulfurous acid is 1.20 if the effect of the second pKa is ignored. B The concentration of sodium hydroxide is 0.05 mol dm–3. C Thymol blue is a suitable indicator to detect the first and second equivalence points. D HSO3− has pKa value of 7.1 and pKb value of 12.1. 13 Phosphoric acid, H3PO4, a tribasic weak acid, has pKa values of 2.1, 7.2 and 12.4. What are the major species present in a solution of phosphoric acid buffered at pH 7? A H3PO4 and HPO42– B H3PO4 and H2PO4– C H2PO4– and HPO42– D HPO42– and PO43–

© Hwa Chong Institution 2021 9729 / 01 / C2 Prelim 2021 7 14 A solution contains Cu 2+(aq), Ni2+(aq), and Zn2+(aq), each of concentration 0.0010 mol dm–3. To selectively precipitate the cations present, H2S was bubbled into the solution until the concentration of S2–(aq) in the solution reaches 1 × 10–19 mol dm–3. The value of the solubility product of each of the sulfides is given below. salt Ksp / mol2 dm–6 CuS 6.3 × 10–36 ZnS 1.6 × 10–24 NiS 4.0 × 10–21 Which statement describes what happens in the solution? A CuS and ZnS only are precipitated B CuS only is precipitated C ZnS and NiS only are precipitated D NiS only is precipitated 15 Use of the D