2024 ANDSS 4E Chem Prelim P2 QP

This document consists of 25 printed pages and 1 blank page. Setter: Mr Edmund Tan O ANDERSON SECONDARY SCHOOL Preliminary Examination 2024 Secondary Four Express CANDIDATE NAME: CLASS: / INDEX NUMBER: CHEMISTRY Paper 2 6092/02 15 Aug 2024 1 hour 45 minutes 0800 – 0945h Candidates answer in the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 26. The use of an approved scientific calculator is expected, where appropriate. Section A 70 Section B 10 Total 80

Preliminary Examinations 4E CHEMISTRY 6092 2024 2 Section A Answer all questions. 1 (a) Use the list of substances to answer the questions. You may use each substance once, more than once or not at all. argon carbon carbon dioxide chlorine iron iron(II) chloride oxygen neon (i) Which two substances are diatomic gases at room temperature? …………………………………………………………………………… ... [1] (ii) Which substance is a compound that contains a transition element? …………………………………………………………………………… ... [1] (iii) Which substance provide an inert environment in light bulbs? …………………………………………………………………………… ... [1] (iv) Which two substances form acidic oxides? …………………………………………………………………………… ... [1] (v) Which two substances produce a solid when added to aqueous silver nitrate? …………………………………………………………………………… ... [1]

Preliminary Examinations 4E CHEMISTRY 6092 2024 3 (b) Table 1.1 describes three processes. Complete Table 1.1 by filling in the missing information. Table 1.1 description of process name of process conversion of polyunsaturated fats to saturated fats formation of an organic compound by the reaction of alcohols and carboxylic acids mixing dilute hydrochloric acid and aqueous sodium hydroxide [3] [Total: 8]

Preliminary Examinations 4E CHEMISTRY 6092 2024 4 2 Mothballs, often used to repel moths and insects, gradually disappear over time when placed in a closed cupboard. A student places some mothballs in a closed cupboard and records its mass over several days. The following data was collected. day mass of mothballs/ g 0 5.0 2 4.6 4 4.2 6 3.8 8 3.4 During the experiment, no liquid or solution was found in the cupboard. A pungent gas was produced and can be detected whenever the cupboard doors are opened. (a) Describe and explain the trend observed in the mass of the mothball over time. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……….. [2] (b) Explain how the concept of diffusion contributes to the observation of pungent smell. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……….. [2] [Total: 4]

Preliminary Examinations 4E CHEMISTRY 6092 2024 5 3 Sustainable aviation fuels (SAFs) are being developed to reduce the carbon footprint of air travel. One method involves collecting used cooking oil from restaurants, processing it to remove impurities such as water and blending it with jet fuel. Fig. 3.1 shows the flow chart outlining the production process of SAFs. + + Fig 3.1 (a) (i) Name the separation process to obtain jet fuel from crude oil. …………………………………………………………………………… ... [1] (ii) Explain how the named process in (a)(i) is used to separate different components of crude oil, including the fraction used as jet fuel. …………………………………………………………………………… ......... …………………………………………………………………………… ......... …………………………………………………………………………… ......... …………………………………………………………………………… ......... …………………………………………………………………………… ... [2] (b) Describe how a separating funnel can be used to separate processed oil from impurities in used cooking oil. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……….. [ 2] SAFs used cooking oil impurities processed oil jet fuel other fractions crude oil

Preliminary Examinations 4E CHEMISTRY 6092 2024 6 (c) Biofuels, like sugarcane -based bioethanol, are alternative energy sources to fossil fuels. Burning of bioethanol releases similar products as burning ethanol. Discuss the concept of the carbon cycle and explain why the burning of bioethanol might not be always considered as carbon neutral. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……………. …………………………………………………………………………… ……….. [3] (d) The equation describes the combustion of ethanol. C2H5OH + 3O2 → 2CO2 + 3H2O Use the information to calculate the enthalpy change for this reaction. bond bond energy kJ/mol bond bond energy kJ/mol C−C 350 C=C 610 C−O 358 O=O 496 C−H 410 C=O 799 O−H 460 enthalpy change = ………………………. kJ [2]

Preliminary Examinations 4E CHEMISTRY 6092 2024 7 (e) Complete the energy profile diagram for the combustion of ethanol. Your diagram should include  the formulae of reactants and products,  the enthalpy change of reaction, and  the activation energy. [3] [Total: 13] energy progress of reaction

Preliminary Examinations 4E CHEMISTRY 6092 2024 8 4 Glutamic acid, an amino acid, is naturally present in the body and in many foods. (a) Glutamic acid is a compound that contains 40.8% carbon, 6.1% hydrogen, 9.5% nitrogen and 43.6% oxygen by mass. Determine the empirical formula of glutamic acid. Show your working clearly. [2] (b) Monosodium glutamate, commonly known as MSG is the sodium salt of glutamic acid. Deduce the charge on the glutamate ion. …………………………………………………………………………… ……….. [1]

Preliminary Examinations 4E CHEMISTRY 6092 2024 9 (c) When amino acids undergo condensation polymerisation, they form a macromolecule. Fig. 4.1 shows the repeat unit of a macromolecule formed by condensation polymerisation. The repeat unit contains five different elements, C, O, N, H and X. Fig. 4.1 (i) Name the type of linkage found in the repeat unit. …………………………………………………………………………… ... [1] (ii) Draw the full structural formula of the two monomers. [2] (iii) Using ideas of valency, suggest an element that could be X. …………………………………………………………………………… ... [1] (d) State the functional group that a molecule must have to undergo addition polymersiation. ………………… …….. ………………………………………………………… ... [1] [Total : 8] N C X C H C C N H H H H O O H

Preliminary Examinations 4E CHEMISTRY 6092 2024 10 5 (a) Lead is extracted by heating its oxide with hydrogen. The equation for the extraction is shown. PbO + H2 → Pb + H2O Fig 5.1 shows the apparatus used for this extraction process. Fig 5.1 (i) Is hydrogen acting as the oxidising agent or reducing agent