Unless there was some reason for us to look deeply into Kobold lore we probably wouldn't know much about the different types.
Now on the other hand if we used a certain type of magic against them and saw that it had no effect, then we would know more and be able to adjust our methods of evisceration.
So it depends on whether or not we can make a Monster Knowledge check (given any +, or -'s depending on type of knowledge and whether studied or not given the quest). With Arcana I can check to see this information and I have a +11 to do so. Looking through the PLHBK page 180 it looks like I would be going against a DC of 25 (for resistances and vulnerabilities). So I would need to roll greater than 14.
Thing I am wondering is whether or not we would have the time to do so. How long would a check like that take, my guess is it would take at least a move action. Considering I am moving currently to cast in the blast radius than it probably wouldn't be until my next turn.
Unless I am looking at it all wrong which occasionally happens...
