For an elementary reaction given below :
A + B → Product
the rate law is :
r = K[A]1[B]1
Molecularity of above reaction will be
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 2
The molecularity of an elementary reaction is the number of reacting species (atoms, ions or molecules) that must collide at the same time for the reaction to occur. It is always a whole number (1, 2 or, rarely, 3) and can never be zero or a fraction. For an elementary reaction, the order equals the molecularity.
Here one molecule of A and one of B collide:
\( \displaystyle \text{Molecularity} = 1 + 1 = 2 \) (bimolecular), which matches the rate law r = k[A]1[B]1, of order 2.