Two hydrocarbons both have the formula C₄H₈. One decolourises bromine water and the other does not. What is the best explanation?
Answer and explanation
Correct answer: D. One is butene (C=C) and the other is cyclobutane (a ring)
- Step 1: C₄H₈ fits CₙH₂ₙ, which is an alkene or a cycloalkane.
- Step 2: Only the alkene has a C=C double bond, so only it adds bromine and decolourises it.
- Step 3: The cycloalkane is saturated and does not react quickly.
Answer
One is butene (C=C) and the other is cyclobutane (a ring).
Why not the others: The two are butene but one is more concentrated: concentration is not the cause. One is butane and the other is cyclobutane: butane has the formula C₄H₁₀. The two are alkanes but one has a branched chain: alkanes do not have the formula C₄H₈.
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