3.13 The reaction F + H H + HF is the rate-limiting elementary step in the...

  

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3.13 The reaction F + H H + HF is the rate-limiting elementary step in the overall reaction H + F 2 HF. This latter process is the key reaction in the HF chemical laser. The reaction proceeds through a transition state: H + F (HHF)* H + HF. Suppose that the activated complex is linear. Some properties of the reac- tants and the activated complex are given in Table 3.2. The threshold energy is estimated to be * = 6.6 kJ mol-. TABLE 3.2 (10-1 m) I (10-47 kg m) v (103 S-) Properties in the F + H Reaction (Problem 3.13) Electronic degeneracy H 2.7 0.46 13.19 1 F 1.8 4 (HHF)* 7.43 12.02 1.19 1.19 4 a. Use collision theory to calculate the preexponential factor and the rate constant for the reaction at 298 K. Compare your answer to the exper- imental result of A = 2 10 L mol- s-. b. Use activated complex theory to calculate the rate constant for the reac- tion at 298 K. Assume that the electronic degeneracy for F and for the activated complex is 4. 3.13 The reaction F + H H + HF is the rate-limiting elementary step in the overall reaction H + F 2 HF. This latter process is the key reaction in the HF chemical laser. The reaction proceeds through a transition state: H + F (HHF)* H + HF. Suppose that the activated complex is linear. Some properties of the reac- tants and the activated complex are given in Table 3.2. The threshold energy is estimated to be * = 6.6 kJ mol-. TABLE 3.2 (10-1 m) I (10-47 kg m) v (103 S-) Properties in the F + H Reaction (Problem 3.13) Electronic degeneracy H 2.7 0.46 13.19 1 F 1.8 4 (HHF)* 7.43 12.02 1.19 1.19 4 a. Use collision theory to calculate the preexponential factor and the rate constant for the reaction at 298 K. Compare your answer to the exper- imental result of A = 2 10 L mol- s-. b. Use activated complex theory to calculate the rate constant for the reac- tion at 298 K. Assume that the electronic degeneracy for F and for the activated complex is 4.