ALKENES [dchemlc]

what is the functional group of alkenes?

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Answer explanation

The alkenes are a homologous series of hydrocarbons which contain a carbon-carbon double bond. The C=C bond is the functional group of the alkenes.

what is the general formula of alkenes?

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Answer explanation

which of the following is not an isomer of C₅H₁₀?

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why are alkenes known as unsaturated hydrocarbons?

• because they contain a C=C double bond

• because they contain a C-C single bond

• because they contain a C-C triple bond

• because they do not contain a hydroxyl group

Answer explanation

Alkenes are unsaturated compounds because they contain a C=C bond. A saturated compound contains single C--C bonds only whereas an unsaturated compound contains one or more double or triple C-C bonds.

what is the empirical formula of alkenes?

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Answer explanation

Alkenes have the general formula C_nH_2n. The number of hydrogen atoms is twice the number of carbon atoms. This means that all alkenes have the same empirical formula, CH₂.

which of the following is not a gas at room temperature?

• pentene

• propene

• butene

• ethene

Answer explanation

Alkenes are gases up to C₄H₈, and the next dozen or so are liquids. Hence, we can see that the members of the homologous series show a trend in physical properties.

what reaction do alkenes undergo?

• addition

• substitution

• neutralization

• multiplication

Answer explanation

Alkenes undergo addition reactions. Part of the double bond breaks to become a single C- C bond and the electrons are used to join other atoms onto the two carbon atoms.

which of the following will not decolourise bromine water?

• ethane

• propene

• butene

• hexene

Answer explanation

If you shake an unknown organic compound with bromine water and the orange bromine water is decolorised (the colour changes from orange to colourless), the compound contains a carbon-carbon double bond.

what will be the name of the product formed when but-2-ene reacts with bromine water?

• 1,2-dibromobutane

• 2,3-dibromobutane

• 3,4-dibromobutane

• 4,5-dibromobutane

what will be produced when alkenes burn in air?

• carbon dioxide

• carbon monoxide

• water

• hydrogen

• carbon (soot)

Answer explanation