The displayed formula of propene is shown. It has three carbon atoms, one of them in a methyl side group. What is the molecular formula of propene?
Question 1 Report
The displayed formula of propene is shown. It has three carbon atoms, one of them in a methyl side group. 
What is the molecular formula of propene?
Answer Details
Read the displayed formula atom by atom. Two carbon atoms are joined by the double bond; the left-hand carbon carries two hydrogen atoms, and the right-hand carbon carries one hydrogen atom and a CH3 group. Adding these gives 2 + 1 = 3 carbon atoms and 2 + 1 + 3 = 6 hydrogen atoms, so propene is C3H6.
C3H8 is propane, the saturated alkane, and choosing it usually means the double bond was ignored. Alkenes follow the general formula CnH2n, so three carbon atoms must carry six hydrogen atoms. C2H4 leaves out the methyl carbon altogether.
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