2023 TMJC H2 Chem Prelim P1 (QP)

2023 H2 Chem Prelim P1 (QP) 2 Use of Data Booklet is relevant to this question. On losing an electron, w hich particle would have the greatest number of unpaired electrons? A C– B Fe3+ C Ti2+ D P 3 Particle X has a charge of +1 and a proton number, n. Particle Y has a proton number of (n+1) and is isoelectronic with X. Which of the following statements correctly describes X and Y? A X and Y are isotopes. B The atoms of X and Y have the same electronic configurations. C Y has a charge of +1 and same charge density as that of X. D Y has a charge of +2 and smaller ionic radius than X. 4 The Valence Shell Electron Pair Repulsion (VSEPR) Theory is used to predict the shapes of molecules or polyatomic ions. Which of the following pairs of species are planar? A F2O and PF5 B SO32– and ClF3 C BrF4– and NO2 D ICl5 and CO2 1 A sample of boron contains two naturally occurring isotopes, 10B and 11B. This sample has a relative atomic mass value of 10.75. What is the percentage of the isotope 11B in the sample? A 20 B 25 C 75 D 80

2 2023 H2 Chem Prelim P1 (QP) Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry 5 Which of these phenomena cannot be explained by hydrogen bonding? 1 NH4Br has a higher boiling point than HBr. 2 Ice is less dense than water. 3 Dimerisation of NO2 to form N2O4. 4 Ethanoic acid forms dimers which dissolved in organic solvents A 1, 3 and 4 only B 1 and 3 only C 2 and 4 only D 1 only 6 A 2.50 dm3 vessel containing ethane gas at a pressure of 1. 50 x 105 Pa is connected to a 7.50 dm 3 vessel containing methane gas at a pressure of 2. 50 x 10 5 Pa. The gases are allowed to mix freely. The temperature of the system is then raised from 100 °C to 350 °C. (Note that there is no chemical reaction between both gases) What is the final pressure of the system? A 2.25 x 105 Pa B 3.76 x 105 Pa C 6.68 x 105 Pa D 7.88 x 105 Pa 7 Which statements concerning only the elements in the third period, sodium to argon, are correct? 1 The element with the highest pH for its chloride in water is sodium. 2 The element with the highest electrical conductivity is aluminium. 3 The element with the highest melting point for its oxide is silicon. 4 The element that has eight atoms in its molecule is sulfur. A 1 and 4 only B 2 and 3 only C 1, 2 and 4 only D 1, 3 and 4 only

3 [Turn over Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry 8 The equations for three reactions are given below: Cl2(g) + H2S(g) → 2HCl(g) + S(s) SO2(g) + 2H2S(g) → 2H2O(l) + 3S(s) Cl2(g) + 2H2O(l) + SO2(g) → 2HCl(aq) + H2SO4(aq) Which is the correct order of strength of the three reacting gases as oxidising agents? Strongest Weakest A Cl2 SO2 H2S B Cl2 H2S SO2 C H2S SO2 Cl2 D SO2 H2S Cl2

4 2023 H2 Chem Prelim P1 (QP) Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry 9 The equation for the reaction of nitrogen monoxide with oxygen is shown below. 2NO(g) + O2(g) ⎯⎯ → 2NO2(g) From initial rate experiments, the following rate equation was derived. rate = k[NO]2[O2] The results of the initial rates experiments are shown. initial [NO] / mol dm−3 initial [O2] / mol dm−3 initial rate of formation of NO2/ mol dm−3 s−1 0.0010 0.002 7.00 x 10−6 0.0020 0.003 a b 0.004 1.26 x 10−4 What are the missing values a and b? a b A 1.9 x 10−5 0.0030 B 1.9 x 10−5 0.0045 C 4.2 x 10−5 0.0030 D 4.2 x 10−5 0.0045 10 Caffeine is a drug that increases the activity of the brain and nervous system. Its elimination from the body follows a first-order kinetics with a half-life of 5.0 h. How long will it take for someone who took 50 m g of caffeine, to have 10 m g of caffeine left in his system? A 5.0 h B 11.6 h C 25.0 h D 58.0 h

5 [Turn over Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry 11 A student carried out an experiment shown below to determine the enthalpy change of combustion of propan-1-ol (Mr = 60.0) . It was found that the combustion of 1.0 g of propan-1-ol raises the temperature of 200 g of water by 40 °C. Given that the enthalpy change of combustion of propan-1-ol is −2200 kJ mol−1, what is the efficiency of the heat transfer process? Assuming the specific heat capacity of water is 4.18 J g–1 K–1. A 88.5 % B 91.2 % C 95.2 % D 99.5 % 12 For the reaction, 3C(s) + Cr2O3(s) ⎯⎯ → 2Cr(s) + 3CO(g) ∆Ho = +1120 kJ mol–1 Which statement is correct? A The reaction is spontaneous at all temperatures. B The reaction is not spontaneous at any temperature. C The reaction is spontaneous only at low temperature. D The reaction is spontaneous only at high temperature. thermometer Lamp containing propan-1-ol calorimeter containing 200g of water

6 2023 H2 Chem Prelim P1 (QP) Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry 13 Gaseous methanol undergoes the following reaction as shown below. CH3OH(g) CO(g) + 2H2(g) Kc = 5.0 mol2 dm–6 Determine the initial concentration of CH3OH such that the equilibrium concentration of CH3OH would be 2.0 mol dm–3. A 3.36 B 4.35 C 4.68 D 5.25 14 Ammonia is commonly used as fertiliser. In an experiment, 0.100 mol dm–3 of ammonia dissociates partially in the presence of water according to the equation below. NH3(aq) + H2O(l) NH4+(aq) + OH– (aq) Which of the following statements is correct? A Kb of ammonia increases upon dilution. B pH remains unchanged upon dilution. C Ammonia acts as a Lewis base. D The degree of dissociation of ammonia remains unchanged upon dilution.

7 [Turn over Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry 15 The numerical value of the solubility product of magnesium phosphate, Mg3(PO4)2, is 1.0 x 10–24. What is the solubility of Mg3(PO4)2? A 1.00 x 10–12 mol dm–3 B 6.21 x 10–6 mol dm–3 C 1.11 x 10–5 mol dm–3 D 1.86 x 10–5 mol dm–3 16 Prismane is an isomer of benzene which has a molecular formula of C 6H6, in which one hydrogen atom is attached to each carbon atom. Prismane is far less stable than benzene. How many di -brominated products , excluding stereoisomers, can Prismane form via free radical substitution? A 2 B 3 C 4 D 5

8 2023 H2 Chem Prelim P1 (QP) Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry 17 Compound J reacts with HCN under suitable conditions to form compound K. Compound J What is the number of  and  bonds in compound K?   A 9 2 B 12 3 C 13 3 D 14 4 18 Pentaerythritol is used as an intermediate in the manufacture of paint. C CH2OHHOCH2 CH2OH CH2OH pentaerythritol Which statement about pentaerythritol is correct? A It can react with HBr(aq) via nucleophilic substitution. B Its empirical and molecular formulae are different. C It can undergo elimination with hot concentrated sulfuric acid to form an alkene. D One mole of pentaerythritol gives two moles of hydrogen gas on reaction with excess sodium.

9 [Turn over Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Chemistry 19 Compound F may be synthesised from methylbenzene. Compound F Which of the following synthetic routes will most likely yield compound F? A nitration → bromination → oxidation → reduction B bromination → oxidation → nitration → reduction C bromination → nitration → oxidation → reduction D nitration → reduction → bromination → oxidation 20 Which of the following could explain why benzene does not undergo electrophilic addition reaction?