2019 TJC H2 Chem Prelim P1 QP

1 9729 / TJC Prelim / 2019 [Turn over TEMASEK JUNIOR COLLEGE 2019 JC2 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9729/01 18th September 2019 1 hour Additional Materials: Multiple Choice Answer Sheet (OMS) Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, Class and index number on the Answer Sheet in the spaces 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 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. This document consists of 16 printed pages including the cover page. Write your name and Civics Group Write and shade your index number

2 9729 / TJC Prelim / 2019 [Turn Over] 1 The number of neutrons and nucleons for five particles are shown below. The letters of the particles do not correspond to the identity of the elements in the Periodic Table. Particle Neutrons Nucleons U 16 33 V- 18 35 S2- 16 32 T2+ 17 34 Q3- 16 31 Which of the following sets consists of particles that are isoelectronic? A U, S2-, T2+ B U, S2-, Q3- C V-, S2-, Q3- D V-, T2+, Q3- 2 Methane was burned in an incorrectly adjusted burner. The methane was converted into a mixture of carbon dioxide and carbon monoxide in the ratio of 95 : 5, together with water vapour. What will be the volume of oxygen consumed when x dm3 of methane is burned? A (x – 2 x05.0 ) dm3 B (x – 0.05x) dm3 C (2x – 2 x05.0 ) dm3 D (2x – 0.05x) dm3

3 9729 / TJC Prelim / 2019 [Turn Over] 3 Which of the following particles contains the most number of unpaired electrons? A Na B P3- C V D Mn2+ 4 Nudic acid B is an acidic antibiotic isolated from the culture medium of the basidiomycete Tricholoma nudum (Bull.) Fr. What is the number of  and  bonds present in the molecule?  A 16 5 B 13 8 C 13 5 D 10 8 5 A pair of compounds have the following properties as described below. (i) The first compound has a larger bond angle about the central atom than the second compound. (ii) The second compound is more polar than the first compound. Which pair of compounds fit the description above? A BCl3, ClO2͞ B ICl2 ͞ , CO2 C HCN, XeF4 D ClO2͞ , CO2

4 9729 / TJC Prelim / 2019 [Turn Over] 6 In which of the following pairs is the melting point of the first member lower than that of the second member? I diamond, silicon II H2O, NH3 III SiCl4, Al2O3 IV Br2, ICl A I, II, III, IV B I, III, IV C III, IV D I only 7 Gaseous Al2Cl6 decomposes into gaseous AlCl3 in a 250 cm 3 closed reaction vessel maintained at a temperature of 500 K. The system reaches equilibrium with a total pressure of 1.16 x 105 Pa. Al2Cl6(g) 2AlCl3(g) The average Mr of the equilibrium gas mixture in the vessel is found to be 214.9. Which of the following statements are correct? 1 The bond angle in both molecules is 120o. 2 The mass of the gaseous mixture inside the reaction vessel is 1.50 g. 3 The following graphs depicts the correct behaviour of the two gases under standard conditions. A 1, 2 and 3 only B 1 and 2 only C 2 and 3 only D 1 only AlCl3 p ideal gas Al2Cl6 1.0

5 9729 / TJC Prelim / 2019 [Turn Over] 8 The following information is given. 2Cr(s) + 3 2 O2(g)  Cr2O3(s) ∆H = −1120 kJ mol−1 3C(s) + Cr2O3(s)  2Cr(s) + 3CO(g) ∆H = +790 kJ mol−1 What is the standard enthalpy change of the following reaction, in kJ mol−1? 2C(s) + O2(g)  2CO(g) A −110 B −220 C −637 D −1273 9 In this question, the symbol ‘<’ means ‘less positive than’ or ‘more negative than’. Both mercury(I) sulfate, Hg2SO4, and cadmium(I) sulfate, Cd2SO4, are odourless white crystalline solids. Hg2SO4 is sparingly soluble while Cd2SO4 is very soluble in water. Both sulfates are used in industry for electrochemical and electrolytic processes. The following data is provided: ∆Hlatto (Hg2SO4) = –2127 kJ mol–1 ∆Hhyd o (Hg+) = –625 kJ mol–1 ∆Hhyd o (SO42–) = –1160 kJ mol–1 Which of the following statements are correct? 1 ∆Hsolno of Hg2SO4 equals to a magnitude of 283 kJ mol-1. 2 ∆Hlatt o of Hg2SO4 is less exothermic than that of Cd2SO4. 3 ∆Gsoln o of Hg2SO4 is < ∆Gsoln o of Cd2SO4 A 1 only B 1 and 2 only C 2 and 3 only D 1,2 and 3 only

6 9729 / TJC Prelim / 2019 [Turn Over] 10 Three electrochemical cells are set up as shown below. The e.m.f in volts at standard conditions is shown on each voltmeter. The concentration of all the solutions are 1 mol dm-3. X, Y and Z are metal electrodes. The e.m.f indicates the order of reactivity of the metals. The order of the strongest to the weakest oxidising agent is : A Z2+, Cu2+, X2+, Y2+ B Y2+, X2+, Cu2+, Z2+ C Cu2+, Z2+, Y2+, X2+ D Z, Cu, X, Y 11 The standard reduction potentials, Eo, for the electrode reactions N O3–/NH4+ and NO3–/NO2 are +0.87 V and +0.81 V respectively. Dilute HC l was added to separate beakers containing 1 mol dm -3 NO3–/NH4+ and 1 mol dm-3 NO3–/NO2 until a pH of 5 was achieved. Which of the following statements are correct for the two beakers? 1 The reducing abilities of NH4+ and NO2 decreases. 2 NO2 is a weaker reducing agent than NH4+ at pH 5. 3 The oxidising ability of NO3– decreases. A 1 only B 3 only C 1 and 2 only D 1,2 and 3 only Cu2+(aq) X2+(aq) Cu X 0.3 Cu2+(aq) Y2+(aq) Cu Y 0.5 Z2+(aq) Cu2+(aq) Z Cu 0.4

7 9729 / TJC Prelim / 2019 [Turn Over] 12 Excess marble chips are added to 30 cm3 of 1 mol dm-3 of nitric acid at room temperature until no further reaction occurs. How would the experiment be different if it is now repeated with 50 cm 3 of 0.5 mol dm-3 of nitric acid at the same temperature? Rate of reaction Amount of products A Faster Lesser B Faster More C Slower More D Slower Lesser 13 CO and H 2 were placed in a reactor fitted with a movable piston and the following equilibrium is established. CO(g) + 2H2(g) ⇌ CH3OH(g) Which of the following best explains what happens when some argon gas is added to the mixture at constant volume and temperature? A The position of equilibrium will not shift as the partial pressure of all gaseous reactants and products remain constant. B The position of equilibrium will not shift as argon does not react with any substance in the mixture. C The position of equilibrium will shift to the right to decrease total pressure. D The position of equilibrium will shift to the left to increase total pressure.

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