Lab 06 -Kinetics of Crystal Violet Lab Report Worksheet 2022-1 copy
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Lab 06 - Kinetics of Crystal Violet
SUMMARY
1.
Provide a brief summary (one or two paragraphs) that describes what you did during the experiment (i.e. the method, not a procedure), what you determined from completing the experiment (i.e. results), and the
validity of your results (i.e. accuracy and precision). (8 pts)
In this experiment, we determined the order of a reaction by graphical method using spectroscopy. We also monitored the dependence of the reaction rate on the initial concentration of reactants. We observed a linear relationship between the increase in the concentration of reactants and an increase of reaction rate. This suggests that we had a first order reaction. Specifically, in first order reactions, doubling the concentration of reactants causes a doubling of the reaction rate. We found that the reaction rate of the solution increased with higher molarities of crystal violet. 2.
Kinetic Run #1: Based on the graphs for the first kinetic runs, what is the order of your reaction? (5 pts)
The order of our reactions was first order.
3.
Attach all three plots (zero, first and second order) to the end of this lab report. If printer is not working be sure to get professors signature before you proceed and close the graphs. (10 pts)
This was submitted during last week’s lab.
1
Reaction Rate Determination
4.
Fill in the table using absorbance values instead of concentration. NOTICE TABLE DOES NOT MATCH THE TABLE IN THE LAB TABLE IN THE PROCEDURE REGARDING PREPARATION – MAKE SURE YOU ARE ENTERING YOUR DATA IN THE PROPER PLACE!
(25 pts)
Run
Solution ∆t
Initial
absorbance at 5 sec
Final
absorbance
At 200 sec
Reaction rate
Absorbance/
t
(show computations
in your lab notebook)
1
(initial)
10 x10
–6
M
(=1.0x10
–5
M)
195s
0.7171
0.1175
-0.00307
2
8 x 10
–6
M
195s
0.5717
0.1044
-0.00240
3
4 x 10
–6 M
195s
0.3012
0.0720
-0.00118
4
2 x 10
–6 M
195s
0.2292
0.0739
-0.000796
5
1 x 10
–6 M
195s
0.1413
0.00455
-0.000701
5.
Based on your results in the table above, compare the changes in concentrations with the changes in reaction rates. (
Use 3 significant figures in all your data and answers for this problem
)
a)
Determine the reaction order by solving the following equations. Show a sample computation in your lab notebook. (Use ln function to solve) (9 pts)
rat e
2
rat e
3
=
[
C V
2
]
x
[
C V
3
]
x
⇔
x
=
¿
1.02
rat e
3
rat e
4
=
[
C V
3
]
x
[
C V
4
]
x
⇔
x
=
¿
0.568
rat e
4
rat e
5
=
[
C V
4
]
x
[
C V
5
]
x
⇔
x
=
¿
0.183
2
What happens to the reaction rate and slope when the concentration (absorbance) of the reactants is doubled
?
Given that the reactants are doubled, the reaction rate will also double. However, since K is independent of concentration, slope will remain the same. b)
Determine the reaction order by solving the following equations. Show a sample computation in your lab notebook. (6 pts)
rat e
2
rat e
4
=
[
C V
2
]
x
[
C V
4
]
x
⇔
x
=
0.796
rat e
3
rat e
5
=
[
C V
3
]
x
[
C V
5
]
x
⇔
x
=
0.376
What happens to the reaction rate and slope when the concentration (absorbance) of the reactants is quadrupled
?
The reaction rate will be quadrupled since it is directly proportional to concentration. Slope will still remain the same. c)
What happens to the reaction rate and slope when the concentration (absorbance) of the reactants is increased 8 times
? Select two appropriate runs to determine the reaction order using the method used
in a) and b). (4 pts)
The reaction rate will increase eight times since it is directly proportional to concentration. Slope will still remain the same. 6.
On average
(compute the average), are the reaction orders you computed in the previous problem consistent with the reaction order determined in the first part of the experiment? (4 pts)
Though the average was 0.589, the reaction order will still remain 1
st
order do the human inaccuracies during experimentation.
7.
What are the possible source of error? Discuss at least two. (4 pts)
The possible sources of error in this lab may have resulted from human inaccuracies. There may have been errors when measuring the concentration of each solution. Similarly, there are limitation in the spectrometer readings. For one, we may have not wiped off all fingerprints or 3
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dust particles which the system may have detected as particulates and thus given a slightly altered reading. We may have also not put in the cuvette exactly when the reaction started to occur.
All calculations (including prelab problems) should be shown in your lab notebook and carbon copy stapled to the back of the report. (5 pts)
4
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