I am familiar with the idea that rate law must be determined experimentally. I am also familiar with the idea that there is no formulated way for coming up with the rate law besides just experimentation.
My question is: why isn't the rate law of:
$$ aA + bB \rightarrow \mbox{something}$$
just:
$$r = k[A]^a[B]^b$$
?
I mean, the equilibrium constant expression involves something to that effect, and the equilibrium constant expression should be precisely talking about when the rates for each direction are equal. So if the rate law is not the above, then why does the equilibrium have that expression?
EDIT: A bit off topic, but how is it possible for something to be zeroth order?