ACJC H2 CHEM P1 QP Prelim

1 © ACJC 2017 9729/01/Prelim/2017 [Turn over ANGLO-CHINESE JUNIOR COLLEGE DEPARTMENT OF CHEMISTRY Preliminary Examination CHEMISTRY 9729/01 Higher 2 Paper 1 Multiple Choice 24 August 2017 1 hour Additional Materials: Optical Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluids. Write your name, index number and tutorial class on the Optical Answer Sheet in the spaces provided unless this has been done for you. 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. Read the instructions on the Optical 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. This document consists of 14 printed pages, including this cover page. 9729/01/Prelim/17 ANGLO-CHINESE JUNIOR COLLEGE © ACJC 2017 Department of Chemistry [Turn over

2 © ACJC 2017 9729/01/Prelim/2017 [Turn over For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 Carbon disulfide is a colo urless volatile liquid with the formula CS2. The compound is used frequently as a building block in organic chemistry as well as an industrial solvent. It reacts with nitrogen monoxide, NO, to form a yellow solid and two gases. These two gases are formed in equal amounts. What are these two gases? A CO2, NO2 B CO2, N2 C CO, N2 D CO2, N2O 2 Use of the Data Booklet is relevant to this question. Which of the following ions will be deflected the most in an electric field? A S2- B Br - C F - D O2- 3 Use of the Data Booklet is relevant to this question. Nuclear magnetic resonance (NMR) spectroscopy is a n analytical t echnique that uses the magnetic properties of certain atomic nuclei in order to elucidate the structure of an organic molecule. Atomic nuclei with an even number of protons and an odd number of neutrons (or vice versa) are most suitable for NMR spectroscopy. Which of the following nuclei is least suitable for NMR spectroscopy? A 28Si B 31P C 103Rh D 19F 4 A 25.00 cm3 sample of a solution of 0.150 mol dm -3 MoOx2- was passed through a Jones redu ctor (a column of zinc powder). It was reduced to Mo 3+. The filtrate required 22.50 cm3 of 0.100 mol dm-3 acidified KMnO4 (aq) to obtain back the original amount of MoOx2-. What is the value of x? A 4 B 3 C 2 D 1

3 © ACJC 2017 9729/01/Prelim/2017 [Turn over 5 Neoxanthin is a major xanthophyll found in green leafy vegetables such as spinach. Which of the following σ bonds are present in neoxanthin? 1 A σ bond formed by sp2–sp3 overlap. 2 A σ bond formed by s–p overlap. 3 A σ bond formed by sp–sp2 overlap. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3 6 The enthalpy changes for the following reactions were measured experimentally: CH3CH2CH3(g) + 5O2(g)  3CO2(g) + 4H2O(l) H = 2202 kJ mol1 H2(g) + ½ O2(g)  H2O(l) H = 286 kJ mol1 CH3C≡CH(g) + 2H2(g)  CH3CH2CH3(g) H = 310 kJ mol1 What is the enthalpy change of combustion of propyne, CH3C≡CH, in terms of kJ mol-1? A -2226 B -1940 C -1606 D -1320 7 35 cm 3 of 0.001 mol dm -3 nitric acid solution was added to 3 5 cm3 of sulfuric acid solution of the same concentration . What is the resulting pH of the combined solution? A 1.5 B 2.5 C 2.8 D 3.0

4 © ACJC 2017 9729/01/Prelim/2017 [Turn over 8 In which of the following pairs is the bond angle in the first species smaller than that in the second species? 1 PBr3, PBr4+ 2 H2Se, H2O 3 SF2, SCl2 A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3 9 X and Y are both ideal gases. X has the smaller molecular mass. Which of the following diagrams correctly describe the behaviour of equal masses of these gases? All temperatures are measured in oC. A B C D temperature P Y X o temperature V X Y o temperature P Y X o temperature V X Y o Constant V Constant V Constant P Constant P

5 © ACJC 2017 9729/01/Prelim/2017 [Turn over 10 X exists in equilibrium with Y and Z. 2X (g) ⇌ Y (g) + Z (g) The concentrations of X, Y and Z varies across time as shown below. Note that the dotted line refers to both concentrations of Y and Z. Which of the following statements is false? A The equilibrium constant is dimensionless. B X(g) was taken out of the system at 20 s. C Given that the temperature was decreased at 35 s, it can be concluded that the forward reaction is endothermic. D Temperature has no effect on the spontaneity of this reaction. 11 The stepwise dissociation equations of phosphoric acid and the corresponding equilibrium constants are shown below. H3PO4 ⇌ H2PO4- + H+ Ka = 7.50 × 10-3 mol dm-3 H2PO4- ⇌ HPO42- + H+ Ka = 6.20 × 10-8 mol dm-3 HPO42- ⇌ PO43- + H+ Ka = 2.20 × 10-13 mol dm-3 A phosphate buffer with pH 7 needs to be prepared. Which is the best way to prepare such a solution? A Dissolving Na3PO4 alone in water. B Dissolving H3PO4 and NaH2PO4 in water. C Dissolving Na2HPO4 and Na3PO4 in water. D Dissolving Na2HPO4 and NaH2PO4 in water.

6 © ACJC 2017 9729/01/Prelim/2017 [Turn over 12 An equilibrium can be represented by the equation below. W (aq) + X (aq) ⇌ Y (aq) + Z (aq) In 0.50 dm3 of a certain mixture, the concentrations of these substances at equilibrium were as shown: Species W X Y Z Concentration / mol dm-3 1.00 2.00 2.00 1.00 A certain amount of Y was added to this equilibrium mixture. What is the number of moles of Y added such that the new equilibrium [ W] is 1.20 mol dm-3? Assume that the temperature remained constant throughout. A 0.10 B 0.20 C 0.75 D 1.50 13 A sample of washing powder which contains a mixture of Na2CO3 and NaHCO3 was titrated with aqueous hydrochloric acid and the following titration curve was obtained. What is the mole ratio of HCO3- to CO32- in the washing powder? A 1:1 B 1:2 C 2:1 D 3:1

7 © ACJC 2017 9729/01/Prelim/2017 [Turn over 14 The table below contains the standard reduction potential values for some cobalt and mercury species. half-equation Eo/ V Co3+ (aq) + e ⇌ Co2+ (aq) +1.82 Co2+ (aq) + 2e ⇌ Co (s) -0.28 Hg2+(aq) + e ⇌ Hg+(aq) +0.91 Hg+(aq) + e ⇌ Hg(l) +0.80 Which one of the following predictions is correct? A Both Co2+ and Hg+ will disproportionate. B Neither Co2+ nor Hg+ will disproportionate. C Only Co2+ will disproportionate. D Only Hg+ will disproportionate. 15 Use of the Data Booklet is relevant to this question. The reaction between iodide and peroxydisulfate (S 2O82-) is slow due to its high activation energy. Which of the following can not function as a catalyst for the above ment ioned reaction? A V2+ B Mn2+ C Mn3+ D Co3+ 16 The decomposition of hydrogen peroxide is a first order reaction. It takes 20 minutes for a 0.140 mol dm -3 solution of hydrogen peroxide to halve its concentration. How much tim