Yeah, except I don't think I ever see it by itself like that. I see "split asunder", "tore asunder", or maybe "came asunder". Just like with "apart", I guess I might see "the two halves of the plate are apart", but could I say "the plate is apart"? I suppose it works if "The couple is asunder". In that case, let's translate this:
I will sunder it asunder and after that sunderance, I'll see it to be asunder, for it will have sundered.
There's a lot of regional variation here. Some people say ta sönder, others prefer göra sönder or ha sönder. According to this article: http://sverigesradio.se/sida/artikel.aspx?programid=411artikel=759942, the most neutral version is ha sönder:
Den karta vi kan rita upp om dessa uttryck visar att ”ha sönder” är det mest standardspråkliga uttrycket, det finns på flest ställen, men är övervägande nordligt. I södra Sverige, Halland, Skåne, Blekinge, Småland säger man ”ta sönder”. I västra Sverige, ungefär Västra Götalands län, ”gör man sönder, och norr därom kommer ”ha sönder”.
To me personally, ha sönder and göra sönder both sound OK, but ta sönder is something I mostly hear from children.
I should add that these three are active verbs for when someone breaks something. When something breaks, like the glass broke, there's only one version: gå sönder, in this case glaset gick sönder.
sönder is actually an adverb. That is why it clashes with the grammar of some native speakers to use it like this - e.g. TobyOak above who considers it ungrammatical. I would never use sönder like this either, personally, but obviously other contributors disagree since it's in the course. :)