1.
Pre-Lab Assignment Kinetics of the Reaction of FD&C; Red #3 with Bleach I. Use Beer's law
to explain how the transmittance of a solution is affected by the concentration of the absorbing
species. 2. What are the units of the rate constant for a) a zero-order reaction; b) a first-order
reaction; c) a second-order reaction; d) a 1/2-order reaction? Express all concentrations in
molarity and time in seconds. 3. Suppose we found that the reaction of Red #3 with bleach is
first-order in hypochlorite. The observed rate constant (kobs) was determined to be 4.00x 10-3sIf
the concentration of hypochlorite was held fixed at 0.134 M, find the specific rate constant (k). 4.
A reaction between the substances A and B (3A+2B2C+D gives the following data: B) Rate of
appearance of C IA] (mol L-) (mol L-) 1.0 x 10-2 1.0x 10-2 3 2.0 x 102 2.0 x 102 3.0 x 10-2
(molL-1h-) 0.3 x 10-6 8.1 x 106 3.24 x 10- 1.20 x 10-6 7.30 x 10 Determine the rate law for the
reaction. 25
Solution
1. According to Beer's law, transmittance is related to concentration of species in solution. So as
the concentration of absorbing species increases, the transmittance goes down and vice versa.
2. Units of rate constant for,
a) zero-order reaction = M/s
b) first-order reaction = 1/s
c) second-order reaction = 1/M.s
d) 1/2-order reaction = M^(1/2)/s
3. specific rate constant here = 4 x 10^-3 s-1/0.134 M = 0.0299 1/M.s