For certain chemical reaction X→Y, the rate of formation of product is plotted against the time as shown in the figure. The number of correct statement/s from the following is _____.
(A) Over all order of this reaction is one
(B) Order of this reaction can't be determined
(C) In region I and III, the reaction is of first and zero order respectively
(D) In region-II, the reaction is of first order
(E) In region-II, the order of reaction is in the range of 0.1 to 0.9.
(A) Over all order of this reaction is one
(B) Order of this reaction can't be determined
(C) In region I and III, the reaction is of first and zero order respectively
(D) In region-II, the reaction is of first order
(E) In region-II, the order of reaction is in the range of 0.1 to 0.9.
Show answer and solution
Answer: 02
Solution
The graph shows three distinct regions: Region I (rate increases with time, curved), Region II (rate is constant, flat plateau), and Region III (rate decreases with time, curved downward).
In Region II, the rate of formation is constant (independent of concentration), which is characteristic of zero-order kinetics locally. In Region I, the rate is increasing — this does not correspond to simple first-order behavior. In Region III, rate decreases, resembling first-order decay. Since the overall rate-time profile shows this sigmoidal/trapezoidal shape with three distinct kinetic regions, the reaction does not follow a single simple integer order throughout. The overall order cannot be assigned as a single clean value from this complex profile.
Therefore, only statement (B) — "Order of this reaction can't be determined" — is correct, giving the answer as 1 correct statement (option 02, i.e., only statement B is correct).
In Region II, the rate of formation is constant (independent of concentration), which is characteristic of zero-order kinetics locally. In Region I, the rate is increasing — this does not correspond to simple first-order behavior. In Region III, rate decreases, resembling first-order decay. Since the overall rate-time profile shows this sigmoidal/trapezoidal shape with three distinct kinetic regions, the reaction does not follow a single simple integer order throughout. The overall order cannot be assigned as a single clean value from this complex profile.
Therefore, only statement (B) — "Order of this reaction can't be determined" — is correct, giving the answer as 1 correct statement (option 02, i.e., only statement B is correct).
[JEE Main 2023 · 29 Jan · Shift 1]