RI 2021 Prelim P1 QP

© Raffles Institution 2021 9729/01/S/21 [Turn Over RAFFLES INSTITUTION 2021 YEAR 6 PRELIMINARY EXAMINATION Higher 2 CHEMISTRY 9729/01 Paper 1 Multiple Choice 23 September 2021 1 hour Additional Materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Do not open this question booklet until you are told to do so. Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, class and index number in the spaces provided on the Answer Sheet. 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 the question booklet. The use of an approved scientific calculator is expected, where appropriate. This document consists of 15 printed pages.

© Raffles Institution 2021 9729/01/S/21 [Turn Over 2 1 The shape of each p-orbital is represented as two lobes. How many electrons does Cu have in orbitals with four lobes? A 7 B 8 C 9 D 10 2 Use of the Data Booklet is relevant to this question. Ionisation energy generally increases across a period. In Period 2, there are two irregularities which cause ionisation energy to be lower than expected. The graph below shows the 2 nd ionisation energies of four consecutive elements with atomic numbers less than 20. What is a possible identity of K? 1 boron 2 carbon 3 oxygen 4 fluorine A 1 and 3 B 2 and 4 C 1 only D 2 only 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 A B C D E F G H J K L M element 2nd ionisation energy

© Raffles Institution 2021 9729/01/S/21 [Turn Over 3 3 Q has the following physical properties. • It is non-volatile. • It does not conduct electricity in its standard state. • It dissolves in water. What is the identity of Q? A nitrogen dioxide B silicon dioxide C sodium D sodium oxide 4 Beryllium is diagonal to aluminium in the Periodic Table and they share similar properties. Which structures for the compounds of beryllium and fluorine are possible? 1 2 3 A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 3 only

© Raffles Institution 2021 9729/01/S/21 [Turn Over 4 5 X, Y and Z are elements in the third period of the Periodic Table. The oxide of X is amphoteric, the oxide of Y is basic and the oxide of Z is acidic. What is the order of increasing ionic radius for these three elements? A X < Y < Z B X < Z < Y C Y < X < Z D Y < Z < X 6 Use of the Data Booklet is relevant to this question. Which metal ion has the highest Ka? A [Co(H2O)6]3+ B [Mg(H2O)6]2+ C [Mn(H2O)6]2+ D [V(H2O)6]3+ 7 The volumes and pressures of e qual masses of four gases CH3OH, SiH4, HBr, and H2Se, are separately investigated, at constant temperature. The results are plotted on a graph of pV against p. Which plot shows the results for CH3OH? 8 Use of the Data Booklet is relevant to this question. Which halogen will not oxidise Fe2+ to Fe3+? A F2 B Cl2 C Br2 D I2 pV p A B C D

© Raffles Institution 2021 9729/01/S/21 [Turn Over 5 9 N2O5 is a compound involved in important atmospheric reactions, such as ozone depletion. It may be formed from N2 and O2 during electric discharge. Given the following data, what is the Hf of N2O5(g)? 2NO(g) + O2(g) ⎯→ 2NO2(g) H = −114.1 kJ mol−1 4NO2(g) + O2(g) ⎯→ 2N2O5(g) H = −110.2 kJ mol−1 N2(g) + O2(g) ⎯→ 2NO(g) H = +180.5 kJ mol−1 A −43.8 kJ mol−1 B −21.9 kJ mol−1 C +11.3 kJ mol−1 D +22.6 kJ mol−1 10 The Haber process involves the following reaction in the presence of an iron catalyst. 3H2(g) + N2(g) ⎯→ 2NH3(g) Which graph shows the effect of increasing partial pressure of N2(g), pN2 , on the initial rate of reaction? A B C D initial rate pN2 initial rate pN2 initial rate pN2 initial rate pN2

© Raffles Institution 2021 9729/01/S/21 [Turn Over 6 11 The reaction in a light stick involves the following reaction. The reaction is first order with respect to the concentrations of both H 2O2 and compound P. In a prototype light stick, where H 2O2 is present in large excess, it was found that the concentration of compound P decreases to 25% of its initial concentration in 1 hour. What is the half-life of the reaction above? A 15 minutes B 30 minutes C 45 minutes D 60 minutes 12 Ozone decomposes naturally into oxygen according to the following equation. The following mechanism has been proposed. K1 is the equilibrium constant of step 1 and k2 is the rate constant of step 2. Which statements are correct for this reaction? 1 The order of reaction with respect to [O3] is 2. 2 The overall rate equation is 2 3 21 2 [O ]rate = [O ] kK . 3 Increasing [O2] slows down the reaction. A 1, 2 and 3 B 1 and 3 only C 1 only D 2 only

© Raffles Institution 2021 9729/01/S/21 [Turn Over 7 13 The Contact process for producing sulfuric acid involves the following reaction. The process is carried out at 450 C and 2 atm. Which statements are correct? 1 At high temperature, more reactant particles have energy higher than the activation energy, thus the rate of production is faster. 2 At high temperature, more reactant particles have energy higher than the activation energy, thus a greater yield is obtained. 3 At high pressure, the rate constant of the reaction is greater, thus the rate of production is faster. 4 The presence of a catalyst increases the rate constant of the reaction, thus the rate of production is faster. A 1, 2 and 3 B 1, 3 and 4 C 1 and 4 only D 2 and 4 only 14 A particular reaction is endothermic. A t high temperature , the ratio of [products] [reactants] at equilibrium is lower than 1. Which graph represents how G changes with temperature for the reaction? G / kJ mol−1 T / K 0 A B C D H = −197 kJ mol−1

© Raffles Institution 2021 9729/01/S/21 [Turn Over 8 15 The value of the ionic product of water, Kw is affected by temperature. temperature / K Kw / 10−14 mol2 dm−6 293 0.681 303 1.47 Which statement is correct? A Water is less acidic at 293 K than at 303 K. B The enthalpy change of ionisation of water is exothermic. C The number of molecules in water increases from 293 K to 303 K. D The concentration of hydroxide ions in water increases from 293 K to 303 K. 16 What is the order of decreasing pKa for these isomers? A P > R > Q B Q > P > R C R > P > Q D R > Q > P 17 A buffer is considered effective in resisting pH changes when the difference between its pH and pKa is not more than 1. A mixture was prepared by mixing 30 cm3 of a 1 mol dm−3 solution of NaOH with 35 cm3 of a 1 mol dm−3 solution of ethanoic acid. (Ka of ethanoic acid = 1.8 × 10−5 mol dm−3) Which statements are correct? 1 The pH of the mixture is 4.74. 2 The mixture can act as an effective buffer. 3 The mixture can better resist pH changes when a small amount of alkali is added than when a small amount of acid is added. A 1, 2 and 3 B 2 and 3 only C 2 only D 3 only

© Raffles Institution 2021 9729/01/S/21 [Turn Over 9 18 In a saturated aqueous solution of mercury( I) bromide, Hg 2Br2, the following equilibrium exists. Hg2Br2(s) ⇌ Hg22+(aq) + 2Br –(aq) Given that the numerical value of the solubility product of mercury(I) bromide is 6.4  10−23, what is the solubility of mercury(I) bromide? A 2.52  10−8