I have this assumption: we can use either passive or active infinitives when there isn't the agent in the sentence and the characteristic belongs to the very thing, for example:
This jalapeno is too spicy to be eaten(the jalapeno itself is spicy)
However, when the characteristic doesn't belong to the thing itself, we can only use active infinitives, e.g:
Coins are pretty easy to find on the ground(not the coins are easy; the finding of them is easy)
But maybe I'm wrong and we can say:
Coins are pretty easy to be found on the ground.
So, please, let me know whether I have failed or not.