2019 - Q19
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Compound X shows three signals in its 13C NMR spectrum.
Treatment of X with hot acidified potassium permanganate produces a compound Y. Compound Y turns blue litmus red.
Compound X produces compound Z upon reaction with hot concentrated sulfuric acid.
Which of the following correctly identifies compounds X, Y and Z?
2022 - Q11
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Cyclohexanol is an alcohol and undergoes a dehydration reaction with sulfuric acid as shown.
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2019 - Q21 (2 marks)
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(a) The structural formula for 2-methylpropan-2-ol is shown in the table.
Draw one structural isomer of this alcohol and state its name.
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2019 - Q23 (6 marks)
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(a) The following apparatus was used in an experiment to determine the molar enthalpy of combustion of ethanol.
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Calculate the experimental molar enthalpy of combustion (ΔcH) of ethanol when 0.370 g ethanol was used to raise the water temperature from 18.5°C to 30.0°C. (4 marks)
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(b) Upon replication, the molar enthalpy of combustion obtained in the experiment was consistently much lower than the accepted value.
Explain ONE change that could be made to the experiment that would improve the accuracy of the obtained value. (2 marks)
2019 - Q32 (4 marks)
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Thiols are the sulfur analogues of alcohols in that the oxygen atom of the alcohol is replaced by a sulfur atom. For example, methanethiol (CH3SH) is the analogue of methanol (CH3OH). The boiling points of some straight chain alcohols and thiols are given in the following graph.
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Explain the patterns of the boiling points shown in the graph.
2020 - Q24 (a) (c) (d) (7 mark)
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Biodiesel, an alternative fuel to diesel, may be produced from vegetable oil. The chemical reaction which converts oils from biomass into biodiesel is shown. R1, R2 and R3 are alkyl chains which may vary from 10 to 22 carbons in length.
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(a) (Identify) Which functional group is present in both the oil and the biodiesel? (1 mark)
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(c) The energy densities of biodiesel and diesel are 38 MJ kg–1 and 43 MJ kg–1 respectively.
The densities of biodiesel and diesel are 0.90 kg L–1 and 0.83 kg L–1 respectively.
When 60.0 L of diesel is combusted in a typical engine, 2141 MJ of energy is released.
(Calculate) what volume of biodiesel would be required to produce the same amount of energy? (2 marks)
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(d) Explain TWO advantages and TWO disadvantages of using bioethanol (ethanol produced from biomass) as an alternative to a fossil fuel. (4 marks)
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2020 - Q29 (5 marks)
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The flow chart shows reactions involving five different organic compounds, A to E .
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Draw the structure of each compound A to E in the corresponding space provided.
2021 - Q25 (4 marks)
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A student conducted an experiment in the school laboratory under standard laboratory conditions (25°C, 100 kPa) to determine the volume of carbon dioxide gas produced during the fermentation of glucose. The following apparatus was set up.
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Calculate the mass of ethanol produced by the fermentation reaction. Include a relevant chemical equation in your answer.
2022 - Q27 (7 marks)
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A bottle labelled ‘propanol’ contains one of two isomers of propanol.
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(a) refer to 7.1 Nomenclature
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(b) refer to 8.2 Analysis of organic substances
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(c) Each isomer produces a different product when oxidised.
Write equations to represent the oxidation reactions of the two isomers. Include reaction conditions. (3 marks)
2022 - Q29 (5 marks)
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The enthalpies of combustion of four alcohols were determined in a school laboratory.
The results are shown in the table.
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(a) Plot the results, including a curved line of best fit, to estimate the enthalpy of combustion of butan-1-ol. (3 marks)
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(b) The published value for the enthalpy of combustion of pentan-1-ol is closer to −3331 kJ mol−1.
Justify ONE possible reason for the difference between the school’s results and published values.
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