The smart chimps do routinely use horrific chemical weapons to kill the ants en masse.
Yes, but it takes a while and depends on if the "ants" are in the "chimps"'s way.
I don't think we could make ants go extinct even if that was our sole purpose as humans. They're extremely adaptable and good generalists, plus they rival us in both total mass and ubiquity, at least outside of tundras. They survived past extinctions, they'll survive us.
As humans? Well, that’s an arbitrary bar. Are you a speciesist?
No, for obvious reasons.
But a bunch of other species did, including some fairly intelligent ones.
In fact, all the species with intelligence approaching or equal to Homo sapiens were wiped out.