2022 TMJC H2 Chem Prelim P1 (QP)

2022 H2 Chem Prelim P1 (QP) Tampines Meridian Junior College 2022 JC2 Preliminary Examination H2 Chemistry 1 In which species are the numbers of protons, neutrons and electrons all different? A F− 9 19 B Na+ 11 23 C P15 31 D S2− 16 32 2 Beams of charged particles are deflected by an electric field. When a beam of protons passes through an electric field of constant strength, the angle of deflection is +12 . In another experiment under identical conditions, particle Y is deflected by an angle of – 4 . What could be the composition of particle Y? protons neutrons electrons 1 1 2 2 2 3 3 5 3 4 5 1 A 1, 2 and 3 B 1 and 2 C 1 only D 3 only 3 Use of the Data Booklet is relevant to this question. In which pair of compounds does the first molecule have a smaller bond angle than the second molecule? A BF3, NH3 B H2O, H2S C BeCl2, SCl2 D XeF4, SiCl4

2 2022 H2 Chem Prelim P1 (QP) Tampines Meridian Junior College 2022 JC2 Preliminary Examination H2 Chemistry 4 To produce decaffeinated coffee, pure liquid CO2 is sometimes used to extract caffeine from coffee beans. It was discovered that the solubility of caffeine greatly increased when a mixture of ethanol and liquid CO2 was used. Which interaction best explains why caffeine is more soluble in the ethanol -CO2 mixture as compared to liquid CO2? A instantaneous dipole - induced dipole interactions B permanent dipole - permanent dipole interactions C hydrogen bonding D dative covalent bond 5 Which graph does not share the same general shape as the other three graphs according to the ideal gas law for a fixed mass of gas with pressure p, volume V and temperature T in Kelvin? A p against 1 V (at constant T) B pV against p (at constant T) C pV against V (at constant T) D V T against T (at constant p)

3 Tampines Meridian Junior College 2022 JC2 Preliminary Examination H2 Chemistry [Turn over 6 Which statements about Group 2 elements are correct? 1 The charge density of cations increases down the Group. 2 The reducing strength of the elements increases down the Group. 3 The minimum temperature needed for the thermal decomposition of Group 2 carbonates increases down the Group. 4 The melting point of MgO is higher than CaO due to the higher polarising power of Mg2+. A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4 7 Due to its radioactive nature, the properties of astatine, At, have to be estimated based on its position in the Periodic Table. Which prediction concerning At or its compounds is correct? A Astatine is a weaker oxidising agent than iodine. B Astatine is a liquid at room temperature. C Astatine forms diatomic molecules which dissociate into atoms less readily than iodine molecules. D Hydrogen astatide has a higher decomposition temperature than hydrogen iodide. 8 Sodium thiosulfate (Na 2S2O3) is used in the textile industry to remove an y excess chlorine from bleaching processes by reducing it to chloride ions. 10 cm 3 of 0.20 mol dm −3 of sodium thiosulfate requires 192 cm 3 of chlorine gas for complete reaction at room temperature and pressure. Which of the following is a possible formula of the sulfur-containing product? A H2S B S C SO2 D HSO4–

4 2022 H2 Chem Prelim P1 (QP) Tampines Meridian Junior College 2022 JC2 Preliminary Examination H2 Chemistry 9 Aqueous solutions of P, Q and R react according to the following equation: P + 3Q + 2R ⎯⎯ → T + U The kinetics of the above reaction was studied and the experimental results obtained are shown in the table below. experiment volume of P / cm3 volume of Q / cm3 volume of R / cm3 volume of water / cm3 relative initial rate 1 20 20 20 20 16 2 20 10 40 10 32 3 10 10 20 40 4 4 20 10 20 30 8 What is the rate equation for the above reaction? A Rate = k[P][Q] B Rate = k[P][Q][R] C Rate = k[P][Q][R]2 D Rate = k[P][Q]2[R]2 10 The following data may be useful for this question. Hf o(N2H4(l)) = +50.6 kJ mol–1 Hf o(N2O4(g)) = +9.2 kJ mol–1 Hf o(H2O(g)) = –241.8 kJ mol–1 Hydrazine, N2H4(l), reacts with dinitrogen tetroxide, N2O4(g), to form nitrogen gas and water vapour. 2N2H4(l) + N2O4(g) ⎯⎯ → 3N2(g) + 4H2O(g) What is the enthalpy change for this reaction? A +1078 kJ mol–1 B –1078 kJ mol–1 C +1754 kJ mol–1 D –1754 kJ mol–1

5 Tampines Meridian Junior College 2022 JC2 Preliminary Examination H2 Chemistry [Turn over 11 Travellers to countries with cold climate may sometimes use heat packs to keep warm. The heat pack is made up of a supersaturated solution of sodium ethanoate and a small metal disc containing very small crystals of sodium ethanoate. When the disc is broken, small crystals of sodium ethanoate are released into the solution to catalyse the crystallisation reaction of sodium ethanoate. What are the correct signs for ∆H and ∆S in this reaction? ∆H ∆S A + – B + + C – + D – – 12 When 0.20 mol of hydrogen gas and 0.15 mol of iodine gas are heated at 723 K until equilibrium is established, the equilibrium mixture is found to contain 0.02 mol of iodine gas. The equation for the reaction is as follows: H2(g) + I2(g) 2HI(g) What is the correct numerical value for the equilibrium constant, Kc? A 12.1 B 48.3 C 92.9 D 185.7 13 Which of the following gives the correct relative strengths of the acids and bases in the reaction? HPO42–(aq) + H2BO3–(aq) H2PO4–(aq) + HBO32–(aq) Kc > 1 acids bases A H2PO4– > H2BO3– HBO32– > HPO42– B H2PO4– > HPO42– HBO32– > H2BO3– C H2BO3– > H2PO4– HPO42– > HBO32– D H2BO3– > HBO32– HPO42– > H2PO4–

6 2022 H2 Chem Prelim P1 (QP) Tampines Meridian Junior College 2022 JC2 Preliminary Examination H2 Chemistry 14 The table below shows the values of the ionic product of water, Kw, at two different temperatures. temperature / oC Kw / mol2 dm–6 25 62 1.00  10–14 1.00  10–13 Which statements are correct for pure water? 1 At 62 oC, pH < 7. 2 At 62 oC, pH = 14 – pOH. 3 The ionic dissociation of water is an exothermic process. A 1 only B 2 only C 1 and 2 D 2 and 3 15 An acidified solution contains 0.10 mol dm –3 of ZnSO4 and 0.10 mol dm –3 of CuSO4. Hydrogen sulfide gas, H 2S, is blown through the solution until it is saturated with H 2S at 15 oC. The concentration of S2–(aq) in the solution reaches 10–35 mol dm–3. The solubility product of ZnS at 15 oC is 10 –24 mol2 dm–6 and that of CuS is 10–40 mol2 dm–6. Which statement describes what happens in the solution? A No precipitate is formed. B ZnS only is precipitated. C CuS only is precipitated. D Both ZnS and CuS are precipitated. 16 (CH3CH2)3CH can react with limited chlorine under uv light to produce monochloro-compounds. How many possible isomers (including stereoisomers) of monochloro -compounds can (CH3CH2)3CH produce? A 3 B 4 C 5 D 6

7 Tampines Meridian Junior College 2022 JC2 Preliminary Examination H2 Chemistry [Turn over 17 Dexamethasone is a corticosteroid commonly used to treat many inflammatory and autoimmune disorders. It received prominence as it showed high efficacy for patients with severe COVID -19 symptoms who need either mechanical ventilation or supplemental oxygen. O F OH H H OH O OH dexamethasone How many possible stereoisomers exist for dexamethasone? A 27 B 28 C 29 D 210 18 Which compounds may be a possible product of the reaction of C 6H5OCOCHBrCH3 with sodium hydroxide under different conditions? 1 C6H5CO2Na 2 CH3CH(OH)CO2Na 3 C6H5OCOCH=CH2 A 1, 2 and 3 B 1 and 2 C 2 and 3 D 3 only

8 2022 H2 Chem Prelim P1 (QP) T