Question

how many isomers are possible in C3N3H9

Answer 1

Explanation:

In this case they are n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, and 2,3-dimethylbutane.

Any formula that goes by CnH2n+2 is an alkane.

There isn't a formula you can use to find out how many isomers there are for any given class of molecules with a specified number of carbons. You just have to think very systematically when you try to find them all.

As far as stereoisomers go, in general alkanes can have different stereoisomers but I don't think there are any for the C6 group of alkanes.