What is the formula of prop-1-ene?
A$C_3H_5$
B$C_3H_4$
C$CH_3CHCH_2$
D$CH_3CCH$
Answer & Solution
Correct answer: C. $CH_3CHCH_2$
1. The ending -ene shows this is an alkene, whose general formula is $C_nH_{2n}$.
2. The stem prop- means three carbon atoms, so $n=3$.
3. Substituting gives $C_3H_6$.
4. Written to show the position of the double bond at carbon 1, that is $CH_3CHCH_2$.
5. $C_3H_4$ fits $C_nH_{2n-2}$, an alkyne, and $C_3H_5$ satisfies no homologous series at all.
_Source: NECTA CSEE 2022 Chemistry 032, Question 1: Multiple Choice Items, item (vi)_
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