A chemist studies the decomposition of dinitrogen pentoxide,

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

Problem

A chemist studies the decomposition of dinitrogen pentoxide, N2O5\mathrm{N_2O_5}, in the gas phase. The following two elementary steps have been proposed: 1. N2O5→NO2+NO3\mathrm{N_2O_5 \rightarrow NO_2 + NO_3} (slow) 2. NO2+NO3→NO+NO2+O2\mathrm{NO_2 + NO_3 \rightarrow NO + NO_2 + O_2} (fast) The chemist adds varying amounts of nitric oxide, NO\mathrm{NO}, to the reaction flask and measures the initial rate of O2\mathrm{O_2} production at 25 ∘C25\,^{\circ}\text{C}. Initial‐rate data
Trial[N2O5]0[\mathrm{N_2O_5}]_0 (mol L−1^{-1})[NO]0[\mathrm{NO}]_0 (mol L−1^{-1})Initial rate of O2\mathrm{O_2} formation (mol L−1^{-1} s−1^{-1})
10.0200.0001.4×10−41.4\times10^{-4}
20.0200.0102.8×10−42.8\times10^{-4}
30.0200.0205.6×10−45.6\times10^{-4}
Answer the following questions. (a) Using the data, determine the experimental order of the reaction with respect to NO\mathrm{NO}. Show your reasoning. (b) Nitric oxide does not appear in either proposed elementary step, yet the data show that it affects the rate. Propose a modification to the mechanism that incorporates NO\mathrm{NO} into an elementary step consistent with the rate law you obtained in part (a). (c) Based on your modified mechanism, classify NO\mathrm{NO} as a catalyst, an intermediate, or a spectator ion. Justify your classification. (d) Explain how the presence of NO\mathrm{NO} changes the overall rate of decomposition of N2O5\mathrm{N_2O_5} without altering the stoichiometry of the net reaction.

Related theory

Browse the problem library