Page 81 - Introduction to chemical reaction engineering and kinetics

3.6 Problems for Chapter 3 63

(ii) By graphical means, find the time required to reach 20%, 50%, and 90% of the
ultimate concentration for each case.
(iii) Compare results of (a) and (b), (b) and (c), (c) and (d), (a) and (e), and (a) and (f).
Explain any differences.
3-11 Diazobenzenechloride decomposes in solution to chlorobenzene and nitrogen (evolved):

C,sHsNzCl(solution) + C6HsCl(solution) + Nz(g)

One liter of solution containing 150 g of diazobenzenechloride is allowed to react at 70°C.
The cumulative volume of N;?(g) collected at 1 bar and 70°C as a function of time is given in
the following table:

tlmin 01 2 3 4 5 6 7
volumeof N& 0 1.66 3.15 4.49 5.71 6181 7.82 8.74
(a) Calculate the concentration of diazobenzenechloride at each time, and hence calculate the
rate of reaction by a difference method for each interval.
(b) What reaction order fits the data?
(c) What is the value (and units) of the rate constant for the reaction order obtained in (b)?