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Ch.14 - Chemical Kinetics
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Capitolo 14, Problema 49a,c

The gas-phase decomposition of NO2, 2 NO2(g) → 2 NO(g) + O2(g), is studied at 383°C, giving the following data:
Time (s) [NO2] (M)
0.0 0.100
5.0 0.017
10.0 0.0090
15.0 0.0062
20.0 0.0047 
(a) Is the reaction first order or second order with respect to the concentration of NO2?
(c) Predict the reaction rates at the beginning of the reaction for initial concentrations of 0.200 M, 0.100 M, and 0.050 M NO2.

Guida verificata passo dopo passo
1
Identify the rate law for the reaction. Since the reaction is 2 NO_2 \(\rightarrow\) 2 NO + O_2, it is likely a second-order reaction with respect to NO_2.
Use the integrated rate law for a second-order reaction: \( \frac{1}{[A]} = kt + \frac{1}{[A]_0} \), where \([A]\) is the concentration of NO_2 at time \(t\), \([A]_0\) is the initial concentration, and \(k\) is the rate constant.
Calculate the rate constant \(k\) using the given data. Choose two data points, for example, \([NO_2]_0 = 0.100\, M\) at \(t = 0\, s\) and \([NO_2] = 0.017\, M\) at \(t = 5.0\, s\), and substitute into the integrated rate law to solve for \(k\).
Once \(k\) is determined, use the rate law \(rate = k[NO_2]^2\) to calculate the initial reaction rates for the given initial concentrations: 0.200 M, 0.100 M, and 0.050 M.
Substitute each initial concentration into the rate law to find the initial rate for each concentration. Remember, the rate is dependent on the square of the concentration for a second-order reaction.

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