Question detail
What is the purpose of using bromine water in the identification of alkenes?
Try the question, check the answer, then read the explanation to understand the curriculum point.
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Question
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exam_style
Style
Topic
Carbon compounds as fuels and feedstock
Question
What is the purpose of using bromine water in the identification of alkenes?
Answer
Bromine water is used to test for the presence of alkenes because alkenes react with bromine, resulting in a color change from brown to colorless. This reaction occurs due to the addition of bromine across the double bond in alkenes.
Explanation
This question tests the student's understanding of chemical tests for functional groups, specifically alkenes. It requires knowledge of the reaction between bromine water and alkenes, demonstrating the student's grasp of organic chemistry concepts.
Common mistake
Misidentifying Bromine Water Reaction
Students think bromine water reacts with alkanes, giving a colour change, and therefore use it to test for alkanes.
Bromine water reacts only with alkenes (and alkynes) because the π bond is attacked, causing the orange–brown colour to disappear. Alkanes lack π bonds and do not react with bromine water, so the colour remains unchanged. Remind students that the test is specific for unsaturated hydrocarbons, not saturated ones.
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