For a reaction:

Rate = k

(i) Write the order and molecularity of this reaction.

(ii) Write the unit of k.

(i) Order: The sum of the exponents (powers) in which the molar concentration is the rate law equation are raised to express the observed rate of the reaction is called the order of reaction. Thus, the order for the given reaction, 2NH₃→ N₂ + 3H₂ is zero order

Molecularity: The number of atoms, ions or molecules that must collide with one another simultaneously so as the result into a chemical reaction is called the molecularity of the reaction. Thus, the molecularity for the given reaction, 2NH₃→ N₂ + 3H₂ is 2 (bimolecular reaction)

(ii) The unit of K is mol L^-1 s^-1

Explanation:

Since concentration is usually expressed in moles/litre and the time

is taken in seconds.

Thus, the unit of the rate of reaction is mol L^-1 s^-1