Question

enumerate the 100 alkanes and its molecular formula

Answer 1

You must be kidding? First, there are many more than 100 alkanes and second, surely you don't expect us to write all of them down for you.

Answer 2

The general formula for alkanes is

CnH(2n+2)

n=1 methane (CH4)
n=2 ethane (C2H6)

and so on to C100H202 or hectane

I don't understand what is meant by "enumerate the 100 alkanes"