Which of the following compounds will decolorize bromine water at room temperature?
Show the answer and explanation
Correct answer
B. Ethene (C2H4)
Principle or equation
Alkenes contain a carbon-carbon double bond, which undergoes addition reactions with bromine water, decolorizing it. Alkanes, alcohols, and haloalkanes do not react with bromine water under these conditions.
Why this answer is correct
Ethene has a C=C double bond. Bromine adds across the double bond, forming 1,2-dibromoethane, so the orange/brown bromine water becomes colorless. Ethane is saturated, ethanol and chloroethane have no double bond, so they do not react.
Example
Propene (C3H6) also decolorizes bromine water, while propane (C3H8) does not.
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