Page 100 - Introduction to chemical reaction engineering and kinetics

82 Chapter 4: Development of the Rate Law for a Simple System

(Millard 1953, p. 453):

t/ruin 0 88 300 412 reaction complete
V/cm3 0 5.9 17.3 22.1 49.5

(a) Write the equations for the reactions occurring during hydrolysis and analysis.
(b) If the reaction is first-order with respect to CHsBr(A), show that the rate constant may be
calculated from k~ = (l/t) ln[VJ(V, - V)], where t is time, V, is the volume of AgN03
required for titration when the reaction is complete, and V is the volume required at any
time during the course of the reaction.
(c) Calculate values of kA to show whether the reaction is first-order with respect to CHsBr.
4-4 Ethyl acetate reacts with sodium hydroxide in aqueous solution to produce sodium acetate and
ethyl alcohol:

CHsCOOC2Hs(A) + NaOH + CHsCOONa + CzHsOH

This saponification reaction can be followed by withdrawing samples from a BR at various
times, adding excess standard acid to “quench” the reaction by neutralizing the unreacted
hydroxide, and titrating the excess acid with base. In a particular experiment at 16”C, samples
of 100 cm3 were withdrawn at various times; the concentration of acid used (HCl) was 0.0416
mol L-l. The following results were obtained (V, is the volume of acid solution required to
neutralize umeacted NaOH at time t) (Glasstone, 1946, p. 1058).
tls 0 224 377 629 816 00
V,/cm3 62.09 54.33 50.60 46.28 43.87 33.06
Using this information, obtain the rate law for the reaction.
4-5 The rate of decomposition of gaseous ethylene oxide (Cz&O), to C& and CO, has been stud-
ied by Mueller and Walters (1951) by determination of the fraction (f~) of oxide (A) reacted
after a definite time interval (t) in a constant-volume batch reactor. In a series of experiments,
the initial pressure of the oxide (PAo) was varied. Some of the results are as follows:

PA&h 27.1 37.2 40.4 55.3 58.6
tls 2664 606 2664 2664 1206
fA 0.268 0.084 0.274 0.286 0.139
From these results, determine the order of reaction and the value of the rate constant (specify
its units).
4-6 The rate of reaction between hydrocyanic acid (HCN) and acetaldehyde (CHsCHO) to give
acetaldehyde cyanohydrin has been studied in a constant-volume batch reactor at 25°C in
dilute aqueous solution, buffered to keep the pH constant (Svirbely and Roth, 1953). The
reaction is

HCN + CH3CH0 -+ CH3CH(OH)CN

A typical set of results is given below, where the concentrations are in mol L-l

tlmin 3.28 11.12 24.43 40.35 67.22 00
CHCN X 10’ 6.57 6.19 5.69 5.15 4.63 2.73
3.84 3.46 2.96 2.42 1.90 0.00
CCH$HO x lo2
Determine the rate law for this reaction at 25”C, and calculate the rate constant, and the initial
concentrations of HCN(CA,) and CHsCHO(ca,).
4-7 The rate of acetylation of benzyl chloride in dilute aqueous solution at 102°C has been studied
by Huang and Dauerman (1969). The reaction is