Consider the gas-phase reaction: H₂(g) + I₂(g) → 2 HI(g) The reaction was experimentally determined to be first order in H₂ and first order in I₂. Consider the proposed mechanisms. Proposed mechanism I: H₂(g) + I₂(g) → 2 HI(g) Single step Proposed mechanism II: I₂(g) Δk1k-12 I(g) Fast H₂( g) + 2 I( g) → k22 HI( g) Slow b. What kind of experimental evidence might lead you to favor mechanism II over mechanism I?

Video transcript

Hi everyone here we have a question asking us to consider the reaction below A plus C forms A C. The reaction is first order in a and first order and see two mechanisms are proposed for the reaction mechanism. One A plus C forms a C mechanism to B plus C. Forms Bc fast and A plus B. C forms A C plus B slow are both mechanisms is valid if yes. What experimental data would you need to identify to favor? Mechanism to? So be plus C. Forms B C is fast, A plus B. C forms A C plus B is slow and it is right determining and the rate equals K. Three times the concentration of a. Terms of concentration of B. C. A plus C forms. Since the concentration of B C is an intermediate, it cannot appear on the rate law. So we will replace it with C. Using the rate law of the first step. So right equals K. One times the concentration of B. Times the concentration of C equals K. Two B. C. So K one B. See equals K two B. C. So our rate equals three K. Three times the concentration of A times K. One Divided by K. two times the concentration of B times the concentration of C. B is the catalyst since it was reformed. So I write equals okay, times the concentration of a times the concentration of C and simplify K. Rate equals K times a time C. And this agrees with the given reaction orders. So yes, it is valid mechanism to might be favored if B. C Is present in large amounts in the solution relative to a sea during the start of the reaction. And this is because the formation is slowest, so our answer is yes. This is valid. Thank you for watching. Bye.