2021 CJC H2 CHEM Prelim P1 QP

1 9729/01 CJC JC2 Preliminary Examination 2021 CANDIDATE NAME CLASS 2T CHEMISTRY 9729/01 Paper 1 Multiple Choice September 2021 1 hour Additional Materials: Multiple Choice Answer Sheet 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 NRIC/FIN 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 12 printed pages. Catholic Junior College JC 2 Preliminary Examinations Higher 2

2 9729/01 CJC JC2 Preliminary Examination 2021 1 Nitrogen exists as a diatomic molecule, N 2. Hydrazine, N2H4, and dinitrogen difluoride, N2F2, are compounds of nitrogen. Which of the following gives the correct number of  bonds in N2, N2H4 and N2F2? number of  bonds in N2 number of  bonds in N2H4 number of  bonds in N2F2 A 2 0 1 B 2 1 1 C 1 1 2 D 3 0 2 2 Aluminium chloride is a covalent compound that forms a dimer with the formula Al2Cl6. A compound of gold and chlorine has a similar molecular formula of Au2Cl6 and has the following structure: The three statements below are properties of the gold compound, Au2Cl6. 1 The oxidation state of the metal is +3. 2 The dimer exists in the vapour phase. 3 The Cl-Au-Cl bond angle is 90o. Which property described is different from that of the aluminium compound, Al2Cl6? A 1 and 2 only B 1, 2 and 3 C 3 only D 2 and 3 only

3 9729 CJC JC2 Preliminary Exam 2021 [Turn over 3 The table below lists three compounds: compound boiling point / oC CH3CH2‒S‒H 35 CH3‒S‒CH3 37 CH3CH2‒O‒H 78 Which of the following statements about the compounds is true? A The C‒S‒H bond angle is larger than the C‒O‒H bond angle because S is larger than O. B CH3CH2‒S‒H has weaker intermolecular hydrogen bonding than CH3CH2‒O‒H. C CH3CH2‒S‒H and CH 3‒S‒CH3 have similar boiling points because they have intermolecular permanent dipole – permanent dipole forces of attraction of similar strengths. D CH3CH2‒O‒H has the highest boiling point because the O‒H bond energy is higher than the S‒H bond energy. 4 Use of the Data Booklet is relevant to this question. An isotope of a metal, Z, undergoes radioactive decay to form helium and an element hafnium, Hf, according to the following equation. Z He2 4 + Hf Given that Hf has a nucleon number of 176, which row correctly shows the identity and composition of Z? identity of Z number of nucleons in Z A tungsten 180 B tungsten 178 C osmium 180 D osmium 178

4 9729/01 CJC JC2 Preliminary Examination 2021 5 Use of the Data Booklet is relevant to this question. The first six ionisation energies of an element, Y, in kJ mol‒1 are shown. 738; 1451; 7733; 10543; 13630; 18020 Y forms an oxide by heating Y with oxygen gas. What is the spdf electronic configuration of Y in its oxide form? A 1s2 2s2 2p6 3s2 3p6 B 1s2 2s2 2p6 C 1s2 2s2 2p6 3s2 D 1s2 2s2 2p6 3s2 3p6 4s2 6 What is the element that has a second ionisation energy lower than that of each of the elements either side of it in the Periodic Table? A boron B nitrogen C oxygen D fluorine 7 Analysis of a mixture of two sulf ur-containing gases show that hydrogen sulf ide, H2S, and carbon sulfide, CS2, are present in a 3 : 1 mole ratio. This mixture is burned in excess oxygen. What will be the CO2 : SO2 mole ratio in the mixture obtained after complete combustion? A 1 : 2 B 1 : 3 C 1 : 4 D 1 : 5 8 Use of the Data Booklet is relevant to this question. A mordant is a soluble salt which forms an acidic aqueous solution and improves the binding of the molecules of a dyestuff to a material. Which solution is least likely to be used as a mordant in the dyeing process? A sodium sulfate B magnesium sulfate C aluminium sulfate D iron(II) sulfate

5 9729 CJC JC2 Preliminary Exam 2021 [Turn over 9 Element X is in Period 3 of the Periodic Table. The following four statements describe the properties of element X or its compounds. Three statements are correct descriptions. One of the statements is not correct because it does not fit with the other three. Which statement is not correct? A Element X is a solid at room temperature which conducts electricity. B The chloride of element X reacts with water to give an acidic solution. C The oxide of element X reacts in water to give an acidic solution. D Adding NaOH(aq) to the solution resulting from the reaction of XCl3 with water produces a white precipitate which is soluble in an excess of NaOH(aq). 10 Which property generally increases down Group 2? A charge density of M2+ ion B electronegativity C melting point D thermal stability of the carbonate 11 A comproportionation reaction is a chemical reaction where two reactants, each containing the same element but with a different oxidation number, form a product in which the elements involved reach the same oxidation number. 2 mol of hydrogen sulfide, H2S, react with 1 mol of another sulfur-containing compound to form 3 mol of elemental sulfur, S, in a comproportionation reaction. What is a possible identity of the sulfur-containing compound? A SO2 B SO3 C H2SO4 D SCl2

6 9729/01 CJC JC2 Preliminary Examination 2021 12 Use of the Data Booklet is relevant to this question. Dinitrogen oxide, N=N=O, burns in ethyne, C 2H2, to produce water vapour, carbon dioxide and nitrogen gas according to the following equation. 5N2O(g) + C2H2(g)  H2O(g) + 2CO2(g) + 5N2(g) The enthalpy change for this reaction is –1668 kJ mol–1 and in dinitrogen oxide, the N=N bond energy has a value of +41 8 kJ mol –1. With reference to other appropriate bond energy data from the Data Booklet, what is the N=O bond energy in dinitrogen oxide? A 344 kJ mol–1 C 1354 kJ mol–1 B 688 kJ mol–1 D 3442 kJ mol–1 13 Which of the following is an endothermic process? 1 The combustion of methane 2 The condensation of steam 3 The electrolysis of water 4 The sublimation of iodine A 1 and 2 only B 2 and 3 only C 3 and 4 only D 1 and 4 only 14 At 1200 K, in the presence of gold catalyst, dinitrogen oxide, N 2O, decomposes according to the equation below. 2N2O(g)  2N2(g) + O2(g) The following data is obtained in an experiment. time, t / s 0 1030 2360 4230 7430 partial pressure of N2O / kPa 25.0 20.0 15.0 10.0 5.0 Which of the following statements is correct? 1 The partial pressure of N2O at any given time is not affected by temperature. 2 The reaction is first order with respect to N2O. 3 The value of the rate constant remains unchanged in the absence of gold. 4 The total pressure at the completion of the reaction can be determined from the above data. A 1 and 2 only B 1 and 3 only C 2 and 4 only D 3 and 4 only

7 9729 CJC JC2 Preliminary Exam 2021 [Turn over 15 The reaction shown below takes place via a one-step mechanism. A(g) + 2B(g) ⇌ C(g) Which of the following statements is most likely to be correct? 1 The yield of C increases at lower pressure. 2 The yield of C decreases when the volume of the reaction vessel is halved. 3 The equilibrium concentration of C is given by the expression: [C] = KC[A][B]2 4 The rate of th