Arrange the reactions, having rate expressions as given below, in the increasing arrangement of the order of reactions:
(A) Rate = k[CHCl3][Cl2]1/2
(B) Rate = k[H2][NO]2
(C) Rate = k[N2O5]
(D) Rate = k[NO2]2
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (C), (A), (D), (B)
The order of a reaction is the sum of the powers of the concentration terms in the experimentally found rate law:
\( \displaystyle \text{Rate}=k[\mathrm{A}]^{x}[\mathrm{B}]^{y}\ \Rightarrow\ \text{order}=x+y \)
The order can be zero, a whole number or a fraction. Adding the powers for each rate law:
(A) Rate = k[CHCl3][Cl2]1/2: order = 1 + 1/2 = 3/2
(B) Rate = k[H2][NO]2: order = 1 + 2 = 3
(C) Rate = k\( \ce{[N2O5]} \): order = 1
(D) Rate = k[NO2]2: order = 2
Shortcut: (C) has the lowest order and (B) the highest. Only Option (2) starts with (C) and ends with (B).