Which of the following compounds would decolorize an aqueous solution of bromine at room temperature?
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Correct answer
C. Ethene
Principle or equation
Alkenes contain a carbon-carbon double bond, which undergoes addition reactions with bromine water, causing the brown color to disappear. Alkanes, alcohols, and haloalkanes do not react with bromine water under these conditions.
Why this answer is correct
Ethene (C2H4) is an alkene with a C=C double bond. It reacts with bromine water to form 1,2-dibromoethane, decolorizing the bromine. Ethane is an alkane, ethanol is an alcohol, and chloroethane is a haloalkane; they do not react with bromine water at room temperature.
Example
C2H4 + Br2 → C2H4Br2 (brown bromine water becomes colorless).
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