14. Hydrocarbons
A section of Chemistry, 9701
Listing 10 of 313 questions
Hexane, C6H14, is a colourless liquid. Two test-tubes contain equal amounts of hexane. 1 cm3 of bromine, Br2, is added to both test‑tubes. One test-tube is kept in the dark and the other is exposed to sunlight. The table describes the appearance of each test-tube after one hour. test-tube conditions observations in the dark no change, mixture remains orange in sunlight colour of mixture fades to pale yellow The test-tube in the dark is kept cool and is not exposed to ultraviolet light. Explain the observations for the test-tube kept in the dark. In sunlight, bromine reacts with hexane by a mechanism which occurs via a series of steps. State the name of the mechanism of the reaction that occurs. Give an equation which shows a propagation step in this reaction in which hexane produces •C6H13. Give an equation which shows a propagation step in this reaction that produces 1-bromohexane. Give an equation which shows a termination step in this reaction that produces 1-bromohexane. A and B are different straight chain alkenes with molecular formula, C6H12. A does not show stereoisomerism. A reacts with potassiummanganate(to form hexane-1,2-diol. Draw the structural formula of A.  State the conditions needed for this reaction of A. B reacts with hydrogen gas in the presence of a platinum catalyst to produce hexane. Name the type of reaction occurring. In terms of σ and π bonds, describe any similarities and differences in the type of carbon‑carbon bonds in B and the type of carbon‑carbon bonds in hexane. 
9701_s20_qp_23
THEORY
2020
Paper 2, Variant 3
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Naphtha is a mixture which contains only hydrocarbon molecules. What is meant by the term hydrocarbon? Name the raw material that is used to produce a sample of naphtha. CompoundV is found in naphtha. It has a molecular formula C10H22. When V is heated at high pressure in the absence of air, an equal number of moles of ethene, propene and W are made. W is a compound made of straight chain, saturated molecules. Name the process that describes this reaction. Deduce the structure of W. Draw its structure below.  Propene is separated from the mixture and heated in air in the presence of a catalyst. Propene is oxidised to X, which contains two functional groups. Effervescence is seen when Na2CO3is added to X. Identify the functional group present in X which is responsible for this observation. Identify a reagent which could be used to show that X contains a C=C. Include relevant observations. X reacts with another reagent to form Y. Molecules of Y react together to form addition polymerZ. The diagram shows the repeat unit of polymerZ. O O– Na+ repeat unit of polymer Z Draw the structural formula of monomerY.  Polymer Z is useful because it absorbs large amounts of water. However, there are problems associated with the disposal of products containing polymer Z. Combustion is not an appropriate method to dispose of pure Z because the process releases harmful gases. Some of these gases contribute to the enhanced greenhouse effect. Identify a gas released during the combustion of Z which contributes to the enhanced greenhouse effect. Identify another gas which could be produced during the combustion of pure Z. Describe a consequence, other than the enhanced greenhouse effect, of its release into the atmosphere. gas consequence  
9701_s21_qp_21
THEORY
2021
Paper 2, Variant 1
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Propene, C3H6, reacts with H2O in the presence of an acid catalyst to form an alcohol with molecular formula C3H8O. Name this type of reaction. Name the catalyst used and state the conditions needed for this reaction to occur. catalyst conditions  Complete the table to show the numbers of sigma (σ) bonds and pi (π) bonds present in propene, C3H6, and C3H8O. σ π C3H6 C3H8O  The reaction of propene, C3H6, with H2O occurs in a two-step mechanism. In step1 C3H6 reacts with the catalyst, H+, to form a carbocation. Draw structures to identify the more stable and less stable carbocations which can form in step1. Explain your answer. more stable carbocation less stable carbocation explanation  Name the major organic product formed from the reaction of propene, C3H6, with H2O. 2-bromopropane reacts to form propene, hydrogen bromide and water under certain conditions. Name this type of reaction. Describe the reagents and conditions needed to favour this reaction. reagents conditions  
9701_s21_qp_21
THEORY
2021
Paper 2, Variant 1
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Alkynes are hydrocarbons that contain one triple C≡C bond. Like alkenes, alkynes take part in addition reactions. A saturated compound can be formed. For example, ethyne, H–C≡C–H, reacts with an excess of hydrogen to form ethane. Propyne, C3H4, undergoes an addition reaction with an excess of hydrogen bromide in two stages. Markovnikov’s rule applies to the addition of HBr at each stage. What is the main product obtained when propyne reacts with an excess of hydrogen bromide?
9701_s23_qp_12
MCQ
2023
Paper 1, Variant 2
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Questions Discovered
313