. For the reaction

2H2(g) + 2NO(g) → N2(g) + 2H2O(g)
The observed rate law is
Rate =k[NO]2[H2]
The mechanisms shown below have been proposed to explain the kinetics of the above reaction
Which of the following are acceptable mechanisms? Explain you answer
Mechanism I
2H2(g) + 2NO(g) → N2(g) + 2H2O(g)
Mechanism II:
H2(g) + NO(g) → N(g) + H2O(g) (slow)
N(g) + NO(g) → N2(g) + O(g) (fast)
H2(g) + O(g) → H2O(g) (fast)
Mechanism III

H2(g) + 2NO(g) → N2O(g) + H2O(g) (slow)
N2O(g) + H2(g) → N2(g) + H2O(g) (fast)

Mech. #3

The original and mech. #3 are both 2nd order and have the same rate law.
Rate law= k[NO]^2[H2]

To determine which mechanisms are acceptable for the given reaction, we need to consider whether the proposed mechanisms align with the observed rate law. Let's compare the rate law with each mechanism:

Mechanism I:
2H2(g) + 2NO(g) → N2(g) + 2H2O(g)

This mechanism matches the balanced equation for the reaction, but it does not follow the observed rate law of Rate = k[NO]2[H2]. Therefore, Mechanism I is not acceptable.

Mechanism II:
H2(g) + NO(g) → N(g) + H2O(g) (slow)
N(g) + NO(g) → N2(g) + O(g) (fast)
H2(g) + O(g) → H2O(g) (fast)

To determine the overall reaction rate, we need to consider the rate-determining step, which is the slowest step in the mechanism. In this case, the rate-determining step is the first reaction: H2(g) + NO(g) → N(g) + H2O(g).

Comparing this rate-determining step with the observed rate law, we find that the concentration of NO is squared, and the concentration of H2 is not. Therefore, Mechanism II does not align with the observed rate law and is not acceptable.

Mechanism III:
H2(g) + 2NO(g) → N2O(g) + H2O(g) (slow)
N2O(g) + H2(g) → N2(g) + H2O(g) (fast)

Again, we need to identify the rate-determining step, which is the first reaction: H2(g) + 2NO(g) → N2O(g) + H2O(g).

Comparing this rate-determining step with the observed rate law, we find that the concentration of NO is squared, and the concentration of H2 is not. Therefore, Mechanism III aligns with the observed rate law and is acceptable.

In conclusion, Mechanism III is the acceptable mechanism for the given reaction as it follows the observed rate law.

GIMME THE ABSOLUTE ANSWER

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