Question

What is the molecularity of an elementary step, given its rate law is as follows: rate = k[a]2[b]?

Answer 1

Chemical reaction: 2A + B → unkwown product.
Molecularity is the number of molecules that come together to react in an elementary (single-step) reaction and Molecularity in chemistry is the number of molecules that come together to react in an elementary (single-step) reaction and is equal to the sum of stoichiometric coefficients of reactants in this elementary reaction.
This reaction is termolecular (or trimolecular) because three molecules react (two A and one B).