Is there a way to know if...

Yes, if it's in a steam redeemable format you can redeem it on steam.

Here's a list.
It's not the full list though.

Try it in Steam, and see what happens. It will tell you it is invalid if it isn't a Steam redeemable key. It will tell you you already own the game if you have it already (so the code doesn't go to waste) or it will add it to your account if it was valid.