Answer:
Mechanism (I).
Explanation:
<em>The given chemical reaction</em><em>: </em>
2NO(g) + O₂(g) → 2NO₂(g)
<em>The given rate equation for the reaction</em><em>:</em>
rate = k [NO]² [O₂]
The rate equation of a given chemical reaction is equal to the product of the concentration of reactants raised to the power the partial orders of reaction.
The overall rate of a given multi-step chemical reaction depends on the slowest step in the reaction mechanism.
Therefore, the slowest step of a given chemical reaction is called the rate-determining step (RDS).
<em>The proposed reaction mechanisms:</em>
(I). 2NO(g) + O₂(g) → 2NO₂(g)
In an elementary (single step) reaction, the rate equation can be written as:
rate = k [NO]² [O₂]
(II). 2NO (g) ===> N₂O₂ (g) [fast]
N₂O₂(g) +O₂(g) ===> 2NO₂ (g) [slow] ⇒ RDS
In an complex (multi-step) reaction, the slow step is the rate determining step (RDS). So, the rate equation can be written as:
rate = k [N₂O₂] [O₂]
(III). 2NO(g) ===>N₂(g) + O₂(g) [fast]
N₂(g) + 2O₂(g) ===> 2NO₂(g) [slow] ⇒ RDS
In an complex (multi-step) reaction, the slow step is the rate determining step (RDS). So, the rate equation can be written as:
rate = k [N₂] [O₂]²
<em>Thus, the rate equation of the reaction mechanism: (I). is the same as the given rate law of the chemical reaction.</em>
<u>Therefore, reaction mechanism (I). is consistent with the rate law of the given chemical reaction.</u>
