Reaction of Alkenes

This lesson covers:

  1. The difference between alkanes and alkenes
  2. What an 'addition reaction' is
  3. How alkenes react with hydrogen, water, and halogens
  4. Distinguishing between alkanes and alkenes using bromine water

Is an alkene a saturated or unsaturated hydrocarbon?

Saturated

Unsaturated

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Which elements do alkenes contain?

(Select all that apply)

Nitrogen

Carbon

Oxygen

Hydrogen

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What is the key difference between alkanes and alkenes?

Alkenes are not a homologous series

Alkenes have a carbon to carbon double bond whereas alkanes do not

Alkenes have oxygen atoms whereas alkanes do not

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What type of reaction can an alkene be part of, because of the carbon to carbon double bond?

Neutralisation reactions

Addition reactions

Condensation reactions

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Addition reaction between an alkene and hydrogen

Chemical equation showing addition reaction between an alkene and hydrogen with a catalyst producing an alkane.

Reacting an alkene with hydrogen gas, and a catalyst, will produce an alkane.


C3H6 + H2 ➔ C3H8

Which compound is produced in the following reaction? 


C3H6 + H2 ➔ ?

Butane C4H10

Hexane C6H14

Pentane C5H12

Propane C3H8

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Addition reaction between an alkene and water

Chemical reaction showing the addition of water to an alkene to form an alcohol with a catalyst at high temperature.

Reacting an alkene with water (at a high temperature and with a catalyst) will produce an alcohol.


C2H4 + H2O ➔ C2H5OH

Which compound is produced in the following reaction? 


C2H4 + H2O ➔ ?

Butanol C4H9OH

Ethanol C2H5OH

Hexanol C6H13OH

Propanol C3H7OH

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An addition reaction between an alkene and water will produce an alcohol.


Once produced, the alcohol will dissolve in the water.


What process can be used to separate the alcohol from the water?

Crystallisation

Filtering

Fractional distillation

Grinding

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Addition reaction between an alkene and a halogen

Equation showing the addition reaction between an alkene and a halogen resulting in a halogenoalkane

Reacting an alkene with a halogen will produce a halogenoalkane.


C2H4 + Br2 ➔ C2H4Br2

Which compound is produced in the following reaction? 


C2H4 + Br2 ➔ ?

Dibromomethane CH2Br2

Dibromoethane C2H4Br2

Dibromopropane C3H6Br2

Dibromobutane C4H8Br2

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Reacting an alkene with a halogen will produce a halogenoalkane.


C4H8 + Br2 ➔ ?


Butene (C4H8) can react with Bromine (Br2) to produce a halogenoalkane.


What halogenoalkane is produced in the reaction?

Dibromopentane C5H10Br2

Dibromohexane C6H12Br2

Dibromobutane C4H8Br2

Dibromopropane C3H6Br2

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An unidentified liquid could be either an alkene or an alkane. To test which one it is, the liquid is reacted with bromine water.


The bromine water turns from orange to colourless.


What type of hydrocarbon is the liquid?

An alkene

An alkane

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