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Multiple Choice
Which of the following molecules is an alkene?
A
(ethene)
B
(ethane)
C
(propane)
D
(ethyne)
Verified step by step guidance
1
Recall the definition of an alkene: an alkene is a hydrocarbon that contains at least one carbon-carbon double bond (C=C).
Examine each molecular formula and identify the type of hydrocarbon it represents based on the general formulas: alkanes (C\_nH\_{2n+2}), alkenes (C\_nH\_{2n}), and alkynes (C\_nH\_{2n-2}).
For C2H4, check if it fits the alkene formula C\_nH\_{2n}. Since for n=2, 2n=4, C2H4 matches the alkene formula, indicating it has a double bond.
For C2H6, compare to the alkane formula C\_nH\_{2n+2}. For n=2, 2n+2=6, so C2H6 is an alkane (ethane) with only single bonds.
For C3H8, similarly, it fits the alkane formula for n=3 (2*3+2=8), so it is propane, an alkane with single bonds; and C2H2 fits the alkyne formula C\_nH\_{2n-2} (2*2-2=2), indicating a triple bond (ethyne).