The reaction 2 , NO _2(g)+ F _2(g) ; ;2 , NO _2 F (g) was studied at 298 K

CHEMISTRY · Multi-part · A Level · Chemistry · Rate equations · Rate equations

Problem

The reaction 2 NO2(g)+F2(g)  ⟶  2 NO2F(g)2\,\text{NO}_2(g)+\text{F}_2(g)\;\longrightarrow\;2\,\text{NO}_2\text{F}(g) was studied at 298 K. A student collected the following initial-rate data:
Trial[NO2_2]0_0 (mol L−1^{-1})[F2_2]0_0 (mol L−1^{-1})Initial rate (mol L−1^{-1} s−1^{-1})
10.100.101.6×10−31.6\times10^{-3}
20.200.103.2×10−33.2\times10^{-3}
30.100.203.2×10−33.2\times10^{-3}
40.300.209.6×10−39.6\times10^{-3}
Two different mechanisms have been proposed. Mechanism A (1) NO2+F2  ⟶  NO2F+F_2+\text{F}_2\;\longrightarrow\;\text{NO}_2\text{F}+\text{F} (slow) (2) NO2+F  ⟶  NO2F_2+\text{F}\;\longrightarrow\;\text{NO}_2\text{F} (fast) Mechanism B (1) NO2+NO2  ⟶  N2O4_2+\text{NO}_2\;\longrightarrow\;\text{N}_2\text{O}_4 (slow) (2) N2_2O4+F2  ⟶  2 NO2F_4+\text{F}_2\;\longrightarrow\;2\,\text{NO}_2\text{F} (fast) Answer the following questions. (a) Using the data in the table, determine the experimental rate law, including the numerical value of the rate constant kk with appropriate units. (b) Show how the molecularity of the slow step in Mechanism A leads to a predicted rate law. Compare the predicted rate law to the experimental rate law from part (a). State whether Mechanism A is consistent with the experimental data and justify your answer. (c) Repeat the analysis for Mechanism B. Clearly state whether it is consistent with the experimental data and justify your reasoning. (d) The student doubles the initial concentration of F2_2 while keeping [NO2_2] constant. Predict the factor by which the initial rate will change. Explain how your prediction follows from the rate law you determined in part (a).

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