2 l alkadiene at normal conditions has a mass equal to 4.82 g. Derive the molecular formula of alkadiene.

Solution: the general formula of alkadiene is CnH2n-2
V = 2 l
m = 4.82 g
V = 2 / 22.4 = 0.09 mol
Mr = 12n + 2n – 2
n = m / Mr ⇔ 0.09 = 4.82 / (14n-2) ⇔ n = 4
The alkadiene formula is C4H6.
Answer: the molecular formula of alkadiene is C4H6.

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