A reaction in which A —–> products was monitored as a function of time and the results are shown below.
Time (s) —- [A] (M)
0 —- 1.000
25 —- 0.914
50 —– 0.829
75 —- 0.744
100 —– 0.659
125 —– 0.573
150 —– 0.488
175 —– 0.403
200 —– 0.318
Okay, well I know the order of the reactions is 0.
Determine the value of the rate constant.
What is the rate of reaction when [A] 0.20 M?
Zero order integrated rate law is:
[A] = [A]₀ – k∙t
[A]₀ denotes initial concentration.
So if you plot [A] versus t you get a straight line with the slope -k.
The result should be something about:
k = 3.4×10⁻³Ms⁻¹
Alternatively you can make regression analysis.
Least square fit of a line of the form
y = k∙x
to a set of data pairs (x,y)
k = ∑(y∙x) / ∑( x² )
(∑ denotes summation over all data points)
For this problem
x = t
y = [A]₀ – [A]
k = 3.41×10⁻³Ms⁻¹
The rate of a zero order reaction is dependent from the concentration level. As long as some reactant is present it will react away at the same, constant rate.:
rate = -d[A]/dt = k = 3.41×10⁻³Ms⁻¹