2023 TJC H2 Chem Prelim P1 (QP)

9729 / TJC PRELIM / 2023 TEMASEK JUNIOR COLLEGE 2023 JC2 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9729/01 Paper 1 Multiple Choice 18 September 2023 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. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C, 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. Write your name & Civics Group on the Answer sheet. Shade your index number in the appropriate boxes. 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 15 printed pages and 1 blank page. Write your name and Civics Group Index number (refer to entry proof)

2 9729 / TJC PRELIM / 2023 1 Magnesium thiocyanate, Mg(SCN) 2, has been found to support heart health by promoting healthy blood circulation and maintaining normal blood pressure levels. What are the numbers of electrons in the magnesium ion and the thiocyanate ion? Magnesium ion Thiocyanate ion A 12 29 B 10 29 C 10 30 D 10 31 2 In which pair of species do both species have only one unpaired p electron? 1 Ar− and F 2 Ar+ and Si+ 3 Ga and C− A 1 and 2 only B 2 and 3 only C 2 only D 3 only 3 The 68Ga isotope is used in positron emission tomography (PET) scan to detect tumors. The radioactive decay of 68Ga isotope has a half-life of 68 days and produces the neutral particle, 68X. This transformation of 68Ga occurs with a proton changing into a neutron. Which of the following statement is incorrect? A 68X has 38 neutrons. B 68X is an isotope of zinc. C There are 3 electrons in the valence shell of 68X. D 2.42 % of the original 68Ga isotope remains after a year.

3 9729 / TJC Prelim / 2023 [Turn over 4 Which of the following species contain at least one unpaired electron? 1 NO 2 NO2 3 NO2− A 1 only B 2 only C 1 and 2 only D 1, 2 and 3 5 Adrenaline is a hormone that is produced by the body during times of stress. What are the bond angles w, x, y and z in adrenaline, from the smallest to the largest? Smallest bond angle ⎯⎯⎯⎯⎯⎯⎯→ Largest bond angle A x z y w B x z w y C y x z w D w y z x

4 9729 / TJC PRELIM / 2023 6 Organic liquids P and Q have identical boiling points. When equal volumes of P and Q are mixed together, there is no reaction and liquid mixture R is obtained. The vapour pressure of liquid mixture R is less than that of liquid P or liquid Q at the same temperature. Which of the following statement is incorrect? A R is less volatile that P. B P and Q are constitutional isomers. C The mixing of P and Q is exothermic. D The average intermolecular forces in R is stronger than that in P or in Q. 7 The following redox reactions have been observed to occur spontaneously. 2VO2+ + H2O2 ⎯⎯ → 2VO2+ + 2H+ S2O82– + H2O2 ⎯⎯ → O2 + 2SO42– + 2H+ Which of the following shows an increasing order of oxidising power? A H2O2 < VO2+ < S2O82– B S2O82– < H2O2 < VO2+ C VO2+ < H2O2 < S2O82– D VO2+ < S2O82– < H2O2 8 Use of the Data Booklet is relevant for this question. A 20 dm3 vessel contains 0.25 mol ammonia gas and a 30 dm3 vessel contains 0.42 mol hydrogen chloride gas . When the two vessels were connected at 500 K, the following chemical reaction occurs : NH3(g) + HCl(g) ⎯⎯ → NH4Cl(s) What is the resultant pressure in Pa in the combined vessel? A 14127 B 20775 C 34902 D 55677

5 9729 / TJC Prelim / 2023 [Turn over 9 Which property of E, F and G will give the trend shown below? Property E F G A boiling point SiCl4 PCl5 BCl3 B volatility HCl HBr HF C solubility in water P4O10 SiO2 MgO D reducing power Mg Ca Ba 10 Use of the Data Booklet is relevant to this question. Element 117, Tennessine, that was discovered in 201 0 is named after the state of Tennessee, USA. Which property is Tennessine, Ts most likely to have? A The covalent radius of Ts is less than 0.140 nm. B The 7p orbitals of a Ts atom are completely filled. C Ts produces bromine from a solution of sodium bromide. D Ts is a dark coloured solid at room temperature and pressure. E F G property

6 9729 / TJC PRELIM / 2023 11 The ore iron(II) chromite, FeCr2O4, is mined in South Africa. The overall reaction for one of the stages in the mining process is as follows: 2Cr2O42– + 3O2 + 4OH– ⎯⎯ → 4CrO42– + 2H2O How many oxygen molecules are required to react completely with one mole of chromite ions? A 4.01 x 1023 B 9.03 x 1023 C 1.81 x 1024 D 5.41 x 1024 12 An energy cycle is drawn to calculate the average bond energy of Br-F bond in BrF3. The enthalpy change of formation of BrF3(l) = –301 kJ mol–1. The enthalpy change of vapourisation of BrF3(l) = +44 kJ mol–1. What is the average bond energy, in kJ mol–1, of the Br–F bond in BrF3? A 152 B 202 C 304 D 404 13 0.05 mol of shiny aluminium foil is added to 0.05 mol of hydrochloric acid and the volume of hydrogen gas produced is measured. The following graph is obtained. Which of the following best explains the changes in the rate of reaction between points P and Q and between points Q and R? between points P and Q between points Q and R A Reaction temperature is increasing Concentration of HCl is decreasing B Reaction temperature is increasing The Al foil is used up. C Reaction temperature is decreasing Concentration of HCl is decreasing D Reaction temperature is decreasing The Al foil is used up. volume of hydrogen / cm3

7 9729 / TJC Prelim / 2023 [Turn over 14 The reaction of hydrogen peroxide with iodide ions in acidic solution can be monitored by an initial rate method. The time taken for a fixed amount of iodine to be produced is measured. H2O2(aq) + 2H+(aq) + 2I–(aq) ⎯⎯ → 2H2O(l) + I2(aq) The table below shows the results obtained from a series of experiments with different volumes of reagent used. experiment number volume of H2O2 / cm3 volume of H+ / cm3 volume of I– / cm3 volume of water / cm3 time taken / s 1 8 8 4 0 30 2 4 8 4 4 60 3 8 4 6 2 20 4 4 8 6 2 40 Which describes the mechanism of this reaction? A H2O2 + H+ H2O + OH+ OH+ + 2I– + H+ H2O + I2 (slow) B H2O2 + I– H2O + IO– (slow) H+ + IO– HIO HIO + H+ + I– I2 + H2O C 2H+ + 2I– 2HI 2HI + H2O2 I2 + 2H2O (slow) D H2O2 + I– + H+ H2O + HIO HIO + I– I2 + OH– (slow) OH– + H+ H2O 15 Ethanoic acid is mixed with ethanol. The ethanol is found to be contaminated with trace amounts of methanol. The following equilibria are established. CH3CO2H(l) + CH3CH2OH(l) ⇌ CH3CO2CH2CH3(l) + H2O(l) Kc = K1 CH3CO2H(l) + CH3OH(l) ⇌ CH3CO2CH3(l) + H2O(l) Kc = K2 Which of the following statements is correct? A Methyl ethanoate will not be produced as there is more ethanol present. B The ratio [CH3CO2CH2CH3] [CH3CO2CH3] = K1 K2