Imagine a sealed chamber with electrodes or an RF coil to turn gases inside into a plasma. Into the chamber we will put methane. There would be only methane inside, no other gas would be present.
Then the methane will be turned into plasma by the electric current. Will it turn into other stable molecules? If yes, how many? For example will it only turn into ethane and ethane will not turn into anything, so the total number of hydrocarbon molecule types will be 2,or will it dissociate the methane into individual hydrogen and carbon atoms and from this create every possible hydrocarbon in existence given long enough time?