11.5 Alkenes (Cambridge (CIE) O Level Chemistry): Flashcards
Exam code: 5070
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What is cracking in the context of crude oil?
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What is cracking in the context of crude oil?
Cracking is the process of breaking down large hydrocarbon molecules into smaller, more useful molecules using a high temperature and a catalyst.
Catalytic cracking requires a high ______ and an alumina or silica ______.
Catalytic cracking requires a high temperature and an alumina or silica catalyst.
What result in the bromine water test confirms that a hydrocarbon is unsaturated?
The orange bromine water turns colourless, confirming the hydrocarbon contains a carbon-carbon double bond and reacts with bromine by addition.
Cracking breaks large alkane molecules into a mixture of smaller ______ and ______ molecules, as well as hydrogen.
Cracking breaks large alkane molecules into a mixture of smaller alkane and alkene molecules, as well as hydrogen.
True or False?
Adding bromine water to an alkane causes the orange colour to disappear.
False.
Alkanes do not react with bromine water, so the orange colour remains unchanged.
A saturated hydrocarbon added to bromine water gives an ______ colour that does not change, showing no reaction has occurred.
A saturated hydrocarbon added to bromine water gives an orange colour that does not change, showing no reaction has occurred.
Why is cracking economically important?
Cracking converts large, less useful fractions such as fuel oil into smaller, high-demand products such as petrol and ethene for the manufacture of plastics.
The hydrogen produced by cracking is used in the ______ Process to manufacture ______ from nitrogen and hydrogen.
The hydrogen produced by cracking is used in the Haber Process to manufacture ammonia from nitrogen and hydrogen.
What is hydrogenation in organic chemistry?
Hydrogenation is the addition of hydrogen across a carbon-carbon double bond, converting an alkene into an alkane.
Ethene reacts with steam at ______°C and 60 atm in the presence of a ______ acid catalyst to form ethanol.
Ethene reacts with steam at 300°C and 60 atm in the presence of a phosphoric acid catalyst to form ethanol.
State the conditions for the hydrogenation of an alkene.
Hydrogenation requires a nickel catalyst.
The industrial production of ethanol by hydration uses ______ as the starting material and ______ as the other reactant.
The industrial production of ethanol by hydration uses ethene as the starting material and steam as the other reactant.
True or False?
Hydrogenation of vegetable oils is used in the manufacture of margarine.
True.
Hydrogenation converts liquid vegetable oils containing C=C double bonds into solid fats used in margarine.
In addition reactions, alkenes react with halogens, hydrogen and steam because the C=C double bond can ______ to form a single bond.
In addition reactions, alkenes react with halogens, hydrogen and steam because the C=C double bond can open to form a single bond.
Why do alkenes undergo addition reactions but alkanes do not?
Alkenes contain a carbon-carbon double bond that can open to allow atoms to add across it, whereas alkanes contain only single bonds and cannot undergo addition reactions.
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