The gas-phase reaction 2NO(g)+O2(g)→2NO2(g) is studied at constant volume in a rigid container. Four experiments are conducted under the conditions below.
Experiment
Initial Partial Pressure of NO (atm)
Initial Partial Pressure of O₂ (atm)
Temperature (K)
Heterogeneous Pt Catalyst Present?
W
0.80
0.20
700
No
X
0.40
0.20
750
No
Y
0.80
0.20
700
Yes
Z
0.40
0.10
750
Yes
Assume the rate law is rate=k[NO]2[O2], where concentrations are proportional to partial pressures under the experimental conditions.
(1) Part 1: (a) Rank the four experiments from fastest to slowest initial rate. Report your answer in the form "___ > ___ > ___ > ___."
(2) Part 2: (b) Provide a detailed justification for each step in your ranking, explicitly addressing how changes in (i) reactant partial pressures, (ii) temperature, and (iii) catalyst presence combine to influence the overall rate.
(3) Part 3: (c) Between Experiments X and Y, conflicting kinetic factors are present. Identify the factor that exerts the dominant control on rate for this pair and justify your conclusion by quantitative or qualitative reasoning appropriate to the data.
(4) Part 4: (d) Suppose a fifth experiment is carried out at 815 K with the same partial pressures as Experiment Z but without the Pt catalyst. Predict whether the rate will be greater than, less than, or approximately equal to the rate in Experiment Z, and defend your prediction with reference to activation energy considerations.