2024 Prelims SAJC H2 Chem P1 (QP)

1 ST ANDREW’S JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS HIGHER 2 CANDIDATE NAME CLASS 2 3 S CHEMISTRY Paper 1 Multiple Choice Candidate answer on the Optical Answer Sheet Additional Materials: Data Booklet 9729/01 11 September 2024 1 hour 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 and D. Choose the one you consider correct and record your choice in soft pencil on the separate Optical Answer Sheet. 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 17 printed pages (including this cover page).

2 1 Use of Data Booklet is relevant to this question. Sodium azide, NaN3, is an ionic salt which is used to inflate airbags inside a car during a crash. How many electrons are there in a sodium ion and an azide ion respectively? sodium ion azide ion A 10 22 B 11 21 C 22 42 D 22 43 2 The first seven successive ionisation energies for element Y are as shown. Y is found in Period 3. 1st 2nd 3rd 4th 5th 6th 7th Ionisation energy / kJ mol–1 1010 1900 2900 5000 6300 21300 25400 Which statements are correct? 1 The valence shell of Y contains only s and p orbitals. 2 The element after Y in the same period has a lower first ionisation energy than Y. 3 Y can react with magnesium metal to form the compound Mg3Y2. A 1, 2 and 3 B 1 and 3 only C 2 and 3 only D 2 only

3 3 The structure of ice is as shown. Which statement is incorrect? A The open structure causes ice to be less dense than liquid water. B The open structure gives ice a smaller mass than liquid water. C Four electrons from each oxygen are involved in forming hydrogen bonds. D Each oxygen atom in a water molecule is tetrahedrally bonded to 4 hydrogen atoms. 4 A sample of pure gas is put into a gas syringe at 27.0 οC and 16 kPa. The plunger of the syringe is pushed in to compress the gas , until the volume occupied is halved. After compression, the pressure of the gas is 40 kPa. What is the new temperature of the gas? A 33.8 οC B 67.5 οC C 102.0 οC D 375.0 οC

4 5 Y is an element in Period 3. In each reaction, Y forms a product in its highest oxidation state. Reaction 1: Chlorine + Y → YaClb Reaction 2: Oxygen + Y → YpOq Which fractions show an increase from sodium to phosphorus? A Both a b and p q B a b only C p q only D Neither a b and p q 6 When dilute sulfuric acid is added to copper(I) oxide, the products formed are copper metal, copper(II) ions and water. Which is correct? number of moles of Cu+ reacted number of moles of Cu formed number of moles of Cu2+ formed A 1 1 1 B 1 2 1 C 2 1 1 D 2 2 1

5 7 Use of the Data Booklet is relevant to this question. In an experiment, 2 g of a fuel is completely burnt. 55% of the energy released is absorbed by 200 g of water and the temperature rose from 18 οC to 66 οC. What is the energy released per gram of fuel burnt? A 20 064 J B 36 480 J C 36 845 J D 72 960 J 8 An energy cycle is given below. Br2(l) + 3F2(g) 2BrF3(l) 2Br(g) + 6F(g) 2BrF3(g) Step III Step II Step I Step IV Which statements are correct? 1 Step I represents the enthalpy change of formation of BrF3(l). 2 Step II involves the breaking of intermolecular instantaneous dipole -induced dipole interactions only. 3 Step III involves the sum of 3 x bond energy of F -F(g) and 2 x enthalpy change of atomisation of Br2(l). A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 3 only

6 9 The reaction between aqueous ethanedioic acid, (COOH) 2, and acidified potassium manganate(VII) produces the following graph. This reaction is carried out in a thermostatically controlled water bath at 60 ⁰C. The products formed are Mn 2+, CO2 and H2O. Which statement is correct? A Before time t, the reaction rate is slow because of the high concentration of (COOH)2. B The temperature used is sufficient to cause the reaction rate to increase after time t. C The presence of more Mn2+ causes the reaction rate to increase after time t. D The reaction rate decreases eventually as the temperature decreases. 10 Azomethane, CH3N=NCH3, undergoes thermal decomposition according to the following equation. This reaction is first order with respect to the concentration of azomethane. CH3N=NCH3(g) → C2H6(g) + N2(g) In an experiment, the initial pressure of azomethane was 30 0 Pa. After 20 minutes of thermal decomposition at 600 K, the pressure of azomethane was 150 Pa. In another experiment, the initial pressure of azomethane was 600 Pa. What would be the final pressure of azomethane after 20 minutes of thermal decomposition at 600 K? A 150 Pa B 300 Pa C 450 Pa D 900 Pa t

7 11 1 mol of N2O4 and 0.2 mol of NO2 were added to a 2 dm3 sealed vessel of fixed volume at 298 K. When the system reached equilibrium, 0.68 mol of NO2 was present in the vessel. N2O4(g) ⇌ 2NO2(g) Which statements are correct? 1 0.76 mol of N2O4 was present at equilibrium. 2 The value of the equilibrium constant, Kc, is 0.608. 3 The pressure in the vessel at equilibrium is lower than the pressure in the vessel before the reaction started. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only 12 10 cm3 of a 0.0100 mol dm–3 solution of sulfuric acid is diluted with 90 cm3 of water. What is the pH of the resulting solution? A 2.65 B 2.70 C 2.95 D 3.00 13 Equal volumes of two solutions are mixed. Which mixtures will result in buffer solutions? 1 0.1 mol dm–3 NaOH with 0.2 mol dm–3 (COOH)2 2 0.2 mol dm–3 CH3NH2 with 0.1 mol dm–3 HBr 3 0.2 mol dm–3 NaOH with 0.1 mol dm–3 H2SO4 A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only

8 14 ZnS is a sparingly soluble salt. ZnS(s) ⇌ Zn2+(aq) + S2–(aq) A sample of ZnS is added to H2S solution, which is a weak dibasic acid. H2S(aq) ⇌ H+(aq) + HS–(aq) HS–(aq) ⇌ H+(aq) + S2–(aq) The pH of the solution is then increased by adding KOH. Which diagram shows how the solubility of ZnS will change with the pH of the solution at a fixed temperature? A B C D

9 15 The structure of a famous anti -cancer drug is as shown. Around Pt, the shape is square planar. NH3 PtH3N Cl Cl Inside the human body, the following reaction takes place. Pt(NH 3)2Cl2 and [Pt(NH3)2(H2O)Cl]+ have different colours. NH3 PtH3N Cl Cl + H2O NH3 PtH3N Cl OH2 + + Cl- Which statements are correct? 1 Pt has an oxidation state of +4. 2 Pt(NH3)2Cl2 can exist as cis-trans isomers. 3 When the Pt complex reacts with H2O, the energy gap between d-orbitals remains the same. A 1, 2 and 3 B 1 and 3 only C 2 and 3 only D 2 only

10 16 Nitrogen monoxide, NO, is an air pollutant which is produced in the internal combustion engine of vehicles. Which reaction occurs in a catalytic converter to decrease the emission of nitrogen monoxide? A NO(g) + CO (g) → NO2(g) + C(s) B NO(g) + CO(g) → ½N2(g) + CO2(g) C NO(g) + CO2(g) → NO2(g) + CO(g) D NO(g) → ½N2(g) + ½O2(g) 17 CH3CH2CH(CH3)CH3 undergoes free radical substitution with chlorine. During the reaction, primary, secondary and tertiary hydrogen atoms are replaced by chlorine atoms at different rates as shown below. Reaction relative rate RCH3 → RCH2Cl 1 R2CH2 → R2CHCl 7 R3CH → R3CCl 21 Which statements regarding the mono-substituted product C5H11Cl are correct? 1 Ratio of CH 2ClCH2CH(CH3)CH3 : CH3CHClCH(CH3)CH3 : CH 3CH2CCl(CH3)CH3 : CH3CH2CH(CH3)CH2Cl is 3 : 14 : 21 : 6. 2 Excess