For each organic compound, determine if it is an alkane, alkene, or alkyne. (No ringed structures and only one multiple bond per structure.)

1. C10H18 - alkyne
2. C15H32 - alkane
3. C20H40 - alkyne
4. C5H10 - alkene
5. C3H6 - alkene
6. C7H16 - alkane
I am not sure on number 3

1 answer

#3 is an alkene.

I don't know how you've been taught to do this but I do it this way.
CnH2n+2 = alkane
CnH2n = alkene (this is C20H40 and C5H10 as well as C3H6)
CnH2n-2 = alkyne