2020 MI Paper 1 Prelim

Class Adm No Candidate Name: This question paper consists of 12 printed pages and 2 blank pages. 2020 Preliminary Examination Pre-University 3 H2 CHEMISTRY 9729/01 Paper 1 Multiple Choice 22 Sep 2020 1h Additional materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Do not turn over this question paper until you are told to do so Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, class and admission number in the spaces provided at the top of this page and on the Multiple Choice Answer Sheet provided. 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 Multiple Choice Answer Sheet provided. Read the instructions on the Multiple Choice 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 question paper. The use of an approved scientific calculator is expected, where appropriate. FOR EXAMINER’S USE TOTAL (30 marks)

2 For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 Which statement about a 36.0 g sample of 18O2 is correct? A There are 6.02 × 1023 18O atoms in the sample. B The number of atoms is the same as the number of atoms in a 32.0 g sample of 16O2. C The number of moles in the sample is the same as the number of moles in a 40.0 g sample of H218O. D The number of molecules is the same as the number of atoms in a 20.0 g sample of H218O. 2 In gold mining, potassium c yanide is used to dissolve gold in order for easier extraction. The equation, commonly known as the Elsner equation, is given below. 4 Au + 8 KCN + O2 + 2H2O ⟶ 4 K[Au(CN)2] + 4 KOH What is the minimum volume of oxygen required to dissolve 1 kg of gold, assuming room temperature and pressure? A 28.8 dm3 B 30.5 dm3 C 461 dm3 D 487 dm3 3 Which of the following experiences the greatest deflection in the same electric field? A 3H+ B 9F- C 12Mg2+ D 32S2- 4 Which of the following pairs have the same molecular shape? A BCl3 and ICl3 B HCN and H2O C CF4 and SF4 D SCl2 and H2S

3 [Turn over 5 Which of the following pairs contains a compound held together by permanent dipole-permanent dipole interactions and a compound containing ionic bonds? A ClO2, AlCl3 B HCl, AlCl3 C NH4Cl, NaCl D HCl, NaCl 6 Which of the following molecules will not form hydrogen bonds with another of its own molecule? A CH3OCH3 B CH3COOH C (CH3)3CNH2 D (CH3)2CHOH 7 To determine the enthalpy change of solution of NH4Cl(s), the enthalpy changes of the following reactions are determined. NH4+(g) ⟶ NH4+(aq) NH4Cl(s) ⟶ NH4+(g) + Cl-(g) Which of the following enthalpy changes is needed in order to determine the enthalpy change of solution of NH4Cl(s)? A The first electron affinity of chlorine atom B The enthalpy change of atomisation of gaseous chlorine molecule C The enthalpy change of hydration of gaseous chloride ion D The enthalpy change of formation of solid ammonium chloride

4 8 Hydrazine, N 2H4, is used as a propellant in spacecraft propulsion. Hydrazine can be manufactured from ammonia using the following reaction. 2NH3(g) + H2O2(l) ⟶ N2H4(l) + 2H2O(l) Using the following information, what is the standard enthalpy change for this reaction in kJ mol-1? Compound ΔHf0 / kJ mol-1 NH3(g) -80.8 H2O2(l) -187.3 N2H4(l) +97.4 H2O(l) -285.8 A -79.7 B -125.3 C +79.7 D +125.3 9 Under which set of conditions will any reaction be spontaneous at all temperatures? ΔH ΔS A positive negative B positive positive C negative positive D negative negative 10 An ideal gas is described as a theoretical gas that obeys the ideal gas equation. Which of the following correctly explains why a real gas deviates from ideal gas behaviour? 1 Real gas molecules travel in a non-random manner. 2 Real gas molecules have a definite volume. 3 Real gas molecules have forces of attraction between them. A 1, 2 and 3 B 1 only C 1 and 3 only D 2 and 3 only

5 [Turn over 11 Which species can act as a Lewis acid? A BF3 B OH- C H2O D NH3 12 In which reaction does ammonia function as a base? 1 2NH3(l) + 2Na(s) ⟶ 2NaNH2(s) + H2(g) 2 NH3(g) + H2O(l) ⟶ NH4+(aq) + OH-(aq) 3 NH3(g) + H2S(g) ⟶ NH4+(g) + HS-(g) A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 2 only 13 The reaction X(g) + 2Y(g) ⟶ Z(g) is found to have the rate equation rate = k[ X] and a rate constant of 1.155 × 10-3 s-1. If the initial concentration of X is 2.50 × 10-3 mol dm-3, what is the concentration of X in mol dm-3 after 30 minutes? A 3.13 × 10-4 B 6.25 × 10-4 C 1.25 × 10-3 D 2.00 × 10-3

6 14 The mechanism for the reaction between nitrogen monoxide and oxygen is believed to be as follows. NO + NO ⇌ N2O2 (fast) O2 + N2O2 ⟶ NO2 + NO2 (slow) Which of the following rate equation is consistent with the mechanism? A rate = k[O2][N2O2] B rate = k[NO]2 C rate = k[NO]2[O2] D rate = k[NO][O2] 15 The following reaction is non-spontaneous under standard conditions. 2NO3-(aq) + 8H+(aq) + 6Cl-(aq) ⇌ 2NO(g) + 4H2O(l) + 3Cl2(g) Which of the following conditions can help to aid the reaction to happen? 1 Adding H2SO4 2 Adding NaNO3 3 Adding NaOH A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only 16 Nitrosyl bromide gas is placed in a vessel of constant volume and an equilibrium is set up. 2NOBr (g) ⇌ 2NO(g) + Br2(g) The total equilibrium pressure is larger than the initial pressure of nitrosyl bromide by 25%. What is the mole fraction, x, of bromine in this equilibrium mixture? A 0.200 B 0.250 C 0.333 D 0.500

7 [Turn over 17 Methanol is produced industrially through the reaction between carbon dioxide and hydrogen, over a copper/zinc-oxide mixture as a catalyst. The reaction is carried out at 50 -100 atm and 250 °C. CO2(g) + 2H2(g) ⇌ CH3OH(g) ΔH <0 Which of the following explains the choice of these conditions? A At lower pressures, the catalyst works more efficiently. B At lower pressures, the rate of formation increases. C At lower temperatures, the rate of formation of methanol increases. D At lower temperatures, the yield of methanol increases. 18 The pKb value for aqueous ammonia at 25 °C is 4.80. What is the pH of a solution containing 50 cm 3 of 0.80 mol dm -3 of aqueous ammonia and 50 cm3 of 0.50 mol dm-3 of nitric acid? A 3.31 B 5.02 C 8.98 D 10.7 19 Phosphoric acid is a weak acid that is sometimes found in soft drinks. It dissociates in water in the manner below: H3PO4(aq) ⇌ H2PO4-(aq) + H+(aq) Ka = 7.1 × 10-3 H2PO4-(aq) ⇌ HPO42-(aq) + H+(aq) Ka = 6.3 × 10-8 Which of the following describes the concentrations of the species present in equilibrium? A [H3PO4] > [H2PO4-] > [HPO42-] B [HPO42-] > [H2PO4-] > [H3PO4] C [H3PO4] > [HPO42-] = [H2PO4-] D [H3PO4] = [H2PO4-] > [HPO42-]

8 20 Two solutions of 20 cm3 of CH3COOH and HCl with the same concentration were respectively titrated against NaOH solution. Which of the following will be the same for both reactions? 1 Initial pH 2 Volume of NaOH required to reach equivalence point 3 pH at equivalence point A 1 only B 2 only C 1, 2 and 3 D 1 and 2 only 21 Magnesium phosphate, Mg 3(PO4)2 is a sparingly soluble salt. If the solubility product of Mg3(PO4)2 is given