Alkenes

Alkenes are unsaturated hydrocarbons with at least one carbon-carbon double bond. Their general formula is CnH2n. They are also called as olefins. The first stable member of alkene series is ethene, which is commonly known as ethylene. Ethene can be prepared in the laboratory by dehydration of ethyl alcohol in presence of sulfuric acid. Ethene is colourless and inflammable gas having a faint sweet odour. It is sparingly soluble in water but highly soluble in organic solvents. Alkenes undergo addition reactions, ozonolysis, polymerization, oxidation and combustion reactions.

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  • Q1

    The orange colour of bromine in CCl4 disappears on adding ethene. This is because

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    Answer:

    two bromine atoms add to ethene.

    Explanation:

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  • Q2

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    Answer:

    Nickel

    Explanation:

    Hydrogenation of ethene to obtain ethane is carried using hydrogen and passing over finely divided platinum or palladium at room temperature or nickel at 200°C.

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  • Q3

    The setup shows laboratory preparation of ethene.

    The reaction taking place here is an example of

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    Answer:

    dehydration reaction.

    Explanation:

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  • Q4

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    Answer:

    120º

    Explanation:

    The H–C–H bond angle in ethene is 120º. It is an alkene.

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  • Q5

    The compound used for artificial ripening of fruits is

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    Answer:

    ethene.

    Explanation:

    The compound ethylene (ethene) is used for artificial ripening of fruits.

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