You are studying the kinetics of the reaction H2(g) + F2(g) †’ 2HF(g) and you wish to determine a mechanism for the reaction. You run the reaction twice by keeping one reactant at a much higher pressure than the other reactant (this lower-pressure reactant begins at 1.000 atm). Unfortunately, you neglect to record which reactant was at the higher pressure, and you forget it later. Your data for the first experiment are as follows:

When you run the second experiment (in which the higher-pressure reactant is run at a much higher pressure), you determine the values of the apparent rate constants to be the same. It also turns out that you find data taken from another person in the lab. This individual found that the reaction proceeds 40.0 times faster at 55oC than at 35oC. You also know, from the energy- level diagram, that there are three steps to the mechanism, and the first step has the highest activation energy. You look up the bond energies of the species involved and they are (in kJ/ mol): HOH (432), FOF (154), and HOF (565).
a. Sketch an energy-level diagram (qualitative) that is consistent with the one described.
b. Develop a reasonable mechanism for the reaction. Support your answer and explain the significance of each piece of information.
c. Which reactant was limiting in the experiments?

Transcribed Image Text:

Pressure of HF (atm) Time (min) 0.300 0.600 0.900 1.200 1.500 30.0 65.8 110.4 169.1 255.9