VJC 2022 JC1 Promo H2 Chem P2 QP

1 © VJC 2022 9729/02/PROMO [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE JC 1 PROMOTIONAL EXAMINATIONS Higher 2 ……………………………………………….………….. …………………………….. CHEMISTRY 9729//02 Paper 2 Structured Questions Candidates answer on the Question Paper. 30 September 2022 2 hours Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your index number, name and CT group in the spaces at the top of this page. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Structured Answer all questions in the spaces provided on the Question Paper. Section B Free Response Answer the question in the spaces provided on the Question Paper. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use S1 /15 S2 /15 E1 /20 E2 /20 Total /70 This document consists of 19 printed pages and 1 blank page.

2 © VJC 2022 9729/02/PROMO [Turn over Section A: Structured Questions [30 marks] Answer all the questions in the spaces provided. S1 (a) The engine capacity of a car refers to the total volume of the combustion cylinders in the engine when the pistons are pushed out of the cylinders. The following experiment was conducted using a test engine where the combustion cylinders have a total volume of 200 cm3. • Ethane gas, CH3CH3, was mixed with air and injected into the cylinders. • The resultant fuel-air mixture (0.0280 mol) was then compressed and ignited. • The pistons are pushed out during the combustion process to bring the volume of the cylinders to a maximum . The final pressure and temperature was recorded to be 1.23 × 106 Pa and 753 oC respectively. (i) Using ideal gas equation, calculate the total number of moles of gaseous species in the cylinder after combustion of the fuel–air mixture. [2] (ii) Using your answer in (a)(i), calculate the change in the total number of moles of gaseous species for the combustion process. [1]

3 © VJC 2022 9729/02/PROMO [Turn over (iii) The complete combustion of 1 mol of ethane gas at 7 53 oC is represented by the following equation: CH3CH3(g) + 7 2 O2(g) → 2CO2(g) + 3H2O(g) Using your answer in (a)(ii), calculate the number of moles of CH3CH3 in the fuel- air mixture. [2] (b) In another experiment, liquid pentane, CH3(CH2)3CH3, was used as the fuel. The energy delivered by the test engine was found to be 2.80 × 104 kJ h–1. Additional data: • Enthalpy change of combustion of liquid pentane = –3510 kJ mol–1 • Density of liquid pentane = 0.626 g cm–3 • Molar mass of pentane = 72.0 g mol–1 (i) Calculate the total amount of energy delivered by the combustion of pentane when the test engine was kept running for two hours. [1]

4 © VJC 2022 9729/02/PROMO [Turn over (ii) Calculate the volume of pentane (in cm 3) required needed to deliver the energy calculated in (b)(i). [2] (c) The fuel energy value (in kJ g–1) of a substance is the heat energy released when 1 g of that substance is combusted. It is known that ethanol, C2H5OH, has a fuel energy value of 23.3 kJ g–1. Liquid ethano l is commonly found in canisters used for portable gas stoves during camping trips. A camper found a left -over canister of ethanol an d carried out an experiment to determine the mass of ethanol left in the canister. This was done using a bomb calorimeter as shown below: In the bomb calorimeter, the bomb was filled with oxygen gas at high pressure and was immersed into a container filled with water. The liquid ethanol was then ignited using ignition wires . T he maximum temperature of the water inside the calorimeter was measured. Additional data: Mass of water used 200 g Change of temperature 24.0 oC Specific heat capacity of water 4.18 J g–1 K–1 Heat capacity of calorimeter (excluding water) 19.3 J K–1

5 © VJC 2022 9729/02/PROMO [Turn over (i) Write an equation for the standard enthalpy change of combustion of liquid ethanol, C2H5OH(l). ……………………………………………………………………………………………… [1] (ii) Using relevant data provided, calculate the mass of ethanol left in the canister. [2] (d) Tetracarbonylnickel, Ni(CO)4, was first synthesised in 1890 by Ludwig Mond by the direct reaction of nickel metal with carbon monoxide. This pioneering work foreshadowed the existence of many other metal carbonyl compounds, including those of vanadium and chromium. Some data for the synthesis of tetracarbonylnickel, Ni(CO)4, are shown below: Equation Ho / kJ mol–1 So / kJ K–1 mol–1 Ni(s) + 4CO(g) → Ni(CO)4(g) –161 –0.420 (i) Explain the significance of the sign of So. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… [2]

6 © VJC 2022 9729/02/PROMO [Turn over (ii) In the axes below, sketch a graph of the Gibbs ’ free energy change ( G) versus temperature (T) for the synthesis of tetracarbonylnickel. Labelling the y-intercept clearly with the correct value. [2] [Total: 15]

7 © VJC 2022 9729/02/PROMO [Turn over S2 (a) (i) Chlorine and bromine react with alkanes via the free -radical substitution mechanism. Outline the mechanism of the reaction between methane and bromine to form bromomethane. [3] (ii) Light of a longer wavelength is lower in energy than light of a shorter wavelength. Bromination of methane can be carried out with light of a longer wavelength (560– 580 nm) while chlorination of methane can only be carried out with light of a shorter wavelength (430–490 nm). Use your answer from (i) to explain why. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. [2]

8 © VJC 2022 9729/02/PROMO [Turn over (b) During the process of chlorination, the relative rates of removing the first hydrogen atom