Lab report Exp 6 HYFLEX Rate Determination and Activation Energy

A lab report of experiment rate determination and activation energy.

Experiment 6
RATE DETERMINATION AND ACTIVATION ENERGY
0
Rate Determination and Activation Energy
OBJECTIVES




To determine the effect of temperature on chemical kinetics.
React solutions of crystal violet and sodium hydroxide at four different temperatures.
Measure and record the effect of temperature on the reaction rate and rate constant.
Calculate the activation energy, Ea, for the reaction.
LECTURE TOPIC REFERENCES
Review the following before performing the experiment:
Chapter Title: Chemical Kinetics
Section Title: The Rate Law: The Effect of Concentration on Reaction Rate; The Effect of
Temperature on Reaction Rate
Tro, N. (2017). Chemistry: A Molecular Approach. 4th Edition. Boston: Pearson. (Or latest edition)
CONCEPTS
An important part of the kinetic analysis of a chemical reaction is to determine the activation
energy, Ea. Activation energy can be defined as the energy necessary to initiate an otherwise
spontaneous chemical reaction so that it will continue to react without the need for additional
energy. An example of activation energy is the combustion of paper. The reaction of cellulose and
oxygen is spontaneous, but you need to initiate the combustion by adding activation energy from
a lit match.
In this experiment you will investigate the reaction of crystal violet with sodium hydroxide. Crystal
violet, in aqueous solution, is often used as an indicator in biochemical testing. The reaction of this
organic molecule with sodium hydroxide can be simplified by abbreviating the chemical formula
for crystal violet as CV+.
CV+ (aq) + OH– (aq) → CVOH (aq)
As the reaction proceeds, the violet-colored CV+ reactant will slowly change to a colorless product,
following the typical behavior of an indicator. You will measure the color change with a
Colorimeter (Figure 1). You can assume that absorbance is directly proportional to the
1
concentration of crystal violet according to Beer’s law (A = cb, where A is absorbance; c is
concentration in M; light path in cm).
The molar concentration of the sodium hydroxide, NaOH, solution will be much greater than the
concentration of crystal violet. This ensures that the reaction, which is first order with respect to
crystal violet, will be first order overall (with respect to all reactants) throughout the experiment.
You will monitor the reaction at different temperatures, while keeping the initial concentrations of
the reactants the same for each trial. In this way, you will observe and measure the effect of
temperature change on the rate of the reaction. From this information you will be able to
calculate the activation energy, Ea, for the reaction.
Figure 1 Colorimeter Schematic Diagram
MATERIALS
Vernier computer interface or LabQuest
Crystallization dish
Computer
ice
Colorimeter
two 10 mL graduated cylinders
Temperature Probe
two scintillation vials
5 plastic cuvettes
30 mL beaker
0.10 M sodium hydroxide, NaOH, solution
watch with a second hand
2.5 × 10–5 M crystal violet solution
PROCEDURE
Note: You will be preparing a series of water baths during this experiment. Measure the temperature
of the water baths in whatever way you wish, but make sure that your measurements are as accurate
as possible.
2
1. Obtain and wear goggles.
2. Calibrate the colorimeter with a blank.
3. Prepare a blank by filling a cuvette 3/4 full with de-ionized water. To correctly use cuvettes,
remember:
• Wipe the outside of each cuvette with a lint-free tissue (Kimwipes).
• Handle cuvettes only by the top edge of the ribbed sides (not the clear sides).
• Dislodge any bubbles by gently tapping the cuvette on a hard surface.
• Always position the cuvette so the light passes through the clear sides. Cover the cuvette.
4. Connect the Colorimeter to the computer interface. Prepare the computer for data collection by
opening the file “35 Activation Energy” from the Advanced Chemistry with Vernier folder of
Logger Pro.
5. Open the Colorimeter lid, insert the blank, and close the lid. Make sure the clear sides of cuvettes
face the light path of the Colorimeter, not the ribbed sides.
6. To calibrate the Colorimeter, press the < or > button on the Colorimeter to select the wavelength
of 565 nm (Green). Press the CAL button until the red LED begins to flash and then release the CAL
button. When the LED stops flashing, the calibration is complete. Remove the cuvette from the
Colorimeter, dispose of the water, dry it with a kimwipe, and save it for Step 8. Click on the
video link https://youtu.be/xs8T_dKsPjg to see how to use the colorimeter with the LabQuest
alone or with a computer.
7.
Prepare the NaOH and crystal violet solutions for the first trial.
a. Use a 10 mL graduated cylinder to obtain 3 mL of 0.10 M NaOH solution. Transfer the solution
to a 20 mL white-capped vial. WARNING: Sodium hydroxide solution, NaOH: Causes skin and
eye irritation.
b. Use another 10 mL graduated cylinder to obtain 3 mL of 2.5 × 10–5 M crystal violet solution.
Transfer the solution to a second 20 mL white-capped vial. WARNING: Aqueous crystal violet:
May be harmful if swallowed. May cause skin irritation and eye damage.
c. Prepare the water bath using a round crystallization dish. Use the hot tap water or ice, as
needed. Note: Fill the dish about half-way to avoid content overflowing and vials floating.
d. Cap the two vials tightly and place them in the water bath. Make sure that the level of the
solutions inside the vials is below the level of the water bath. The vials containing the
solutions should be in the water bath for at least one minute.
8. Conduct the first trial at approximately 25 oC. Be ready to time the reaction.
a. Check the temperature of the water bath; it should be holding steady at or near 25°C.
(Note: If room temperature is 25 oC or higher, better to lower the target temperature to
about 23-24 oC).
3
b. Dip the temperature probe in the NaOH inside the vial to make sure it is also holding steady at
25°C (again, preferably 1 to 2 oC lower than this target temperature if room temperature is
25 oC or higher as the temperature may go up after 1 minute reaction time). Once this
desired temperature is achieved, carefully pour the NaOH and crystal violet solution into a
30 mL beaker. Start timing the reaction using the second hand on your watch (you may use
your mobile phone, but make sure to clean it after the lab). Let the reaction run for one
minute before proceeding to Step c (while carefully stirring with the temperature probe).
Make sure to hold the beaker inside the water bath while stirring to avoid reaction content
spillage.
c. After letting the reaction to run for one minute from Step b, record the temperature of the
reaction mixture on the Data and Calculations section.
d. Fill a clean, dry cuvette (preferably the cuvette from step 6 or use a similar cuvette) about 3/4
full with the reaction mixture. Cover the cuvette. Clean the clear sides of cuvette with a
Kimwipe and place it properly (clear sides along the light path) inside the Colorimeter. Close
the lid on the Colorimeter. Promptly conduct this step to minimize erroneous results.
e. Click
. The default settings are 0.25 sample per second for 180 seconds. You may click
to end the data collection early (You may set the time to collect data for 60 seconds
by clicking the
icon). Observe the progress of the reaction.
f. When data collection is complete, carefully remove the cuvette from the Colorimeter. Dispose
of the contents of the beaker and cuvette as directed.
9. You learned from the Concept section of this procedure that the reaction is first order with respect
to crystal violet, hence, you can determine the rate constant, k, by plotting a graph of ln
Absorbance vs. time by performing the following steps.
a. Choose New Calculated Column from the Data menu.
b. Enter “ln Absorbance” as the Name, and leave the unit blank.
c. Enter the correct formula for the column into the Equation edit box by choosing “ln” from the
Function list, and selecting “Absorbance” from the Variables list. Click
.
d. Click the y-axis label. Choose ln Absorbance. A graph of ln absorbance vs. time should now be
displayed. Change the graph scale, if needed (Click the Autoscale icon on the menu bar).
e. Click Linear Regression, . Record the slope value in your data table as the rate constant, k.
Read the PROCESSING THE DATA section to guide you in interpreting the graph.
f. Properly label (e.g. Figure 1, then provide the title for the first graph) and save the graph (Go
to menu bar and click on File, then Save As).
10. Follow Steps 7 to 9 to collect the data and create graphs for the other trials. Choose “Clear Latest
Run” from the Experiment menu to create a new graph.
11. Repeat the necessary steps to complete trials 1–3. The next trials will be at ~20°C, ~15°C, and
~10°C. (Note: Include all four graphs in your lab report.) Note: See Sample graphs below.
4
SAMPLE GRAPHS
Sample Graph 1. Crystal Violet and Sodium Hydroxide Reaction (Zoom in to >200% for clarity)
Sample Graph 2. Crystal Violet and Sodium Hydroxide Reaction (Zoom in to >200% for clarity)
5
Sample Graph 3. Crystal Violet and Sodium Hydroxide Reaction (Zoom in to >200% for clarity)
Sample Graph 4. Crystal Violet and Sodium Hydroxide Reaction (Zoom in to >200% for clarity)
6
PROCESSING THE DATA
As CV+ decomposes, its purple color fades away, which makes CV+ a perfect indicator of the rate of
reaction. Since the rate of reaction is first-order with respect to the concentration of CV+, and the
disappearance of purple color CV+ (timing until color of CV+ dissipates) represents the concentration of
CV+, which indicates the rate of reaction, collecting and recording the absorbance readings as the
reaction proceeds (after one minute of mixing and maintaining the desired temperature setting) can
be graphed using the Vernier colorimeter set at 565 nm. The Absorbance of the mixture in the
Colorimeter is directly proportional to the concentration of Crystal Violet (Beer’s Law). Consequently,
Absorbance (A) can be substituted directly for the (CV+), so the equation then becomes
In [A]t = – kt + In [A]0
(Equation 1)
Since the reaction is first order with respect to CV+, the integrated rate law for the first order reaction
above will be used to obtain the rate constant, k. As you can see, the above equation shows a linear
relationship between the natural log of absorbance and time, t. Using the general equation of a
straight line (y = mx + b) to plot the integrated rate law equation for the first order reaction (Equation
1), a graph of ln [A] vs time can be created, which generated a straight line with a negative slope.
Using the graph of absorbance vs. time, convert the absorbance to In Absorbance on the y-axis, and
plot it against the time (60s). If the resulting graph gives a straight line with a negative slope, it
confirms that the rate of CV+ and OH- reaction is first order with respect to CV+, the negative slope (m)
represents the rate constant, k, in the integrated rate law equation.
In [A]
m=-k
In [A]t = -kt + In [A]0
y = mx + b
t
Figure 2 Natural Log of Absorbance versus Time (seconds)
Using the negative k from the graph in the integrated rate law equation for the first-order reaction
with respect to CV+, that is – (-k). Therefore, a negative times a negative means the k becomes
positive. Rate constants are supposed to be positive.
7
Once all the rate constants, k, are graphically determined at four different temperatures, the
Arrhenius equation can be manipulated or simplified to allow the graphical determination of
activation energy, Ea.
The original Arrhenius Equation shows the other factors that affect the E a:
K = Ae- Ea/RT
(Equation 2)
Represents the correct frequency of
collision with correct orientation.
Fraction of molecules with enough energy
to cross the energy barrier (Ea)
Manipulated or simplified Arrhenius equation (to obtain the straight line relationship) becomes:
−𝐸𝑎
𝐼
In k = [ 𝑅 ] [𝑇] + 𝐼𝑛 𝐴
(Equation 3)
This requires converting k to In k and t (oC) to T (Kelvins) and calculating 1/T. Since Equation 3
represents a linear relationship between ln k and 1/T, the data points can be plotted to determine
the slope, m.
In k
𝐼
𝑇
Figure 3 Natural Log of Rate Constant versus the Reciprocal of Absolute Temperature
Using Equation 3 and the slope, m, of the trend line, the energy of activation, Ea, can be calculated:

𝐸𝑎
𝑅
=-m
Ea = m x R
(where, R = 8.314 J/k . mol)
If the Ea is low, the energy required to start the reaction is low, hence the time it takes to start the
reaction is short.
8
LAB SAFETY AND WASTE DISPOSAL
Waste Disposal:
Collect and dispose of wastes from Trials I to IV, in the inorganic waste bottle. Dispose of unused crystal
violet in the organic waste bottle, and unused NaOH in the inorganic waste bottle. All waste bottles are
located in the Satellite Accumulation Area (SAA).
Lab Safety:
Wear the appropriate Personal Protected Equipment (PPE). Read all Safety Data Sheets (SDSs) provided by
instructor. Pay attention to the safety precautions mentioned in the procedure and by the instructor.
BIBLIOGRAPHY
Randall, J. and Volz, D. (2017). Advanced Chemistry with Vernier, 3rd edition. Rate Determination
and Activation Energy. Beaverton, OR: Vernier Software and Technology.
9
DATA AND CALCULATIONS
Trial
Temperature
(°C)
Rate constant, k
(s–1)
1
2
3
4
DATA ANALYSIS
1. Plot a graph of your data above, using temperature (°C) as the x-axis, and the rate constant, k,
as the y-axis.
a. Disconnect your Colorimeter and temperature probe from the interface.
b. Choose New from the File menu. An empty graph and table will be created in Logger Pro.
c. Double click on the x-axis heading on the table, enter a name and unit, then enter the four
values for the rate constant from your data table above.
Note: Attach this graph you created in your lab report as Figure 5 (title the graph properly).
Describe the relationship between rate constant (k) and temperature.
2. Determine the activation energy, Ea, by plotting the natural log of k (ln k) vs. the reciprocal of
absolute temperature (1/T). Note: Absolute temperature, T = oC + 273.
a. Choose New Calculated Column from the Data menu.
b. Create a column, ln rate constant, k.
c. Create a second column, reciprocal of absolute temperature, 1/(Temperature ( oC) + 273).
d. On the displayed graph, plot ln rate constants (ln k) on the y-axis and the reciprocal of
absolute temperature (1/T) on the x-axis by clicking on the respective axes labels. Autoscale
the graph if necessary.
Note: Attach this graph you created in your lab report as Figure 6 (title the graph properly).
Describe the relationship between ln k vs. 1/T.
10
3. Calculate the activation energy, Ea, for the reaction. To do this, first calculate the best fit line
equation (use linear fit) for the data in Step 2. Record the slope, m, of the linear fit below and
use it to calculate the activation energy, Ea, in units of kJ/mol.
Note: On a plot of ln k vs. 1/T,
Ea = m × R.
4. A well-known approximation in chemistry states that the rate of a reaction often doubles for
every 10°C increase in temperature. Use your data to test this rule. (Note: It is not necessarily
equal to 2.00; this is just an approximate value, and depends on the activation energy for the
reaction.)
CALCULATIONS:
Slope, m : ________________________________________________
Activation Energy, Ea (kJ/mol) : _______________________________
11
LABORATORY REPORT PREPARATION GUIDE
MASTER SQL
EXPERIMENT 6 Rate Determination and Activation Energy
I. Introduction
1. What does rate constant indicate in the rate law?
2. What is the well-known approximation in chemistry about the effect of temperature on the reaction rate?
3. What does the activation energy of a reaction indicate in terms of the effect of temperature on starting the reaction?
4. What does the Arrhenius Theory indicate in regards to the effect of temperature and other factors on the reaction
rate?
5. What were the objectives of this experiment?
6. How was the rate constant determined in this experiment?
7. What data were collected in this experiment?
8. Why is Beer’s law important in interpreting these data?
9. What were the hazards in this experiment and the safety precautions you implemented to reduce the risk of these
hazards?
II. Results Analysis
A. Data and Calculations
Summarize the important results here and refer the reader to the attached Data Sheet for details and calculations.
B. Discussion
1. What chemical reaction was performed to study the effect of temperature on the reaction rate? Show the equation.
2. What is the order of this reaction with respect to crystal violet?
3. How were the data gathered using the colorimeter?
4. What were the qualitative and quantitative signs of reaction completion?
5. How were gathered data manipulated to calculate the rate constant (k values) using the integrated rate law for the
first-order reaction? Support your answer using your graph.
6. What happened to the k values as the temperature increases? Support your answer using your graph.
7. Using the k values at different temperatures, how was the activation energy determined by graphical method?
Support your answer using your graph.
8. What equation was used to determine the activation energy of the crystal violet and sodium hydroxide reaction?
9. What is the activation energy of the reaction? What does this mean?
III. Conclusions
1. What conclusion can be drawn from the relationship between temperature and rate constant?
2. What happened to the rate constant when the temperature was increased by 10oC?
3. What was the activation energy of the reaction and what does this value indicate in relation to the rate of the
reaction?
4. If results were inconclusive, what could have happened that hindered your group from obtaining the desired results.
5. What could your group have done to avoid this error?
6. What is the importance of the concepts learned in this experiment? Give one practical application.
LABORATORY REPORT
Experiment 6 Rate Determination and Activation Energy
Name: ____________________________________________
Lab Partner’s Name: _________________________________
I. Introduction
II. Results Analysis
A. Data
Date: ___________________
Score: _________________
B. Discussion
III. Conclusion
References (APA Style)
ATTACHMENT 1
DATA AND CALCULATIONS
Trial
Temperature
(°C)
Rate constant, k *
(s–1)
1
2
3
4
* Note: Attach all graphs supporting the rate constant determinations.
DATA ANALYSIS
1. Plot a graph of your data above, using temperature (°C) as the x-axis, and the rate constant,
k, as the y-axis. Describe the relationship between rate constant (k) and temperature.
2. Determine the activation energy, Ea, by plotting the natural log of k (ln k) vs. the reciprocal
of absolute temperature (1/T). Absolute temperature (T) = oC + 273). Note: Attach this
graph you created in your lab report (title the graph properly). Describe the relationship
between ln k vs. 1/T.
3. Calculate the activation energy, Ea, for the reaction. To do this, first determine the best fit
line equation for your data in Step 2. Use the slope, m, of the linear fit to calculate the
activation energy, Ea, in units of kJ/mol. Note: On a plot of ln k vs. 1/absolute temperature,
Ea = m × R.
Calculations:
Slope, m : ________________________________________________
Activation Energy, Ea (kJ/mol) : _______________________________
4. A well-known approximation in chemistry states that the rate of a reaction often doubles
for every 10°C increase in temperature. Use your data to test this rule. (Note: It is not
necessarily equal to 2.00; this is just an approximate value, and depends on the activation
energy for the reaction.). Show your analysis below.

Don't use plagiarized sources. Get Your Custom Essay on
Lab report Exp 6 HYFLEX Rate Determination and Activation Energy
Just from $13/Page
Order Essay
Calculate the price
Make an order in advance and get the best price
Pages (550 words)
$0.00
*Price with a welcome 15% discount applied.
Pro tip: If you want to save more money and pay the lowest price, you need to set a more extended deadline.
We know how difficult it is to be a student these days. That's why our prices are one of the most affordable on the market, and there are no hidden fees.

Instead, we offer bonuses, discounts, and free services to make your experience outstanding.
How it works
Receive a 100% original paper that will pass Turnitin from a top essay writing service
step 1
Upload your instructions
Fill out the order form and provide paper details. You can even attach screenshots or add additional instructions later. If something is not clear or missing, the writer will contact you for clarification.
Pro service tips
How to get the most out of your experience with Writall
One writer throughout the entire course
If you like the writer, you can hire them again. Just copy & paste their ID on the order form ("Preferred Writer's ID" field). This way, your vocabulary will be uniform, and the writer will be aware of your needs.
The same paper from different writers
You can order essay or any other work from two different writers to choose the best one or give another version to a friend. This can be done through the add-on "Same paper from another writer."
Copy of sources used by the writer
Our college essay writers work with ScienceDirect and other databases. They can send you articles or materials used in PDF or through screenshots. Just tick the "Copy of sources" field on the order form.
Testimonials
See why 20k+ students have chosen us as their sole writing assistance provider
Check out the latest reviews and opinions submitted by real customers worldwide and make an informed decision.
Other
Great work as always
Customer 454983, January 28th, 2022
Nursing
Absolutely incredible service. Thank you
Customer 454925, May 15th, 2022
Business Studies
Excellent work
Customer 454241, November 28th, 2020
Computer science
Great Job!!
Customer 455111, November 15th, 2021
Law
Amazing work! 10/10
Customer 455105, December 5th, 2021
Health Care
I got an A and got a good feedback from the instructor. Thanks
Customer 453877, May 20th, 2020
Philosophy
Amazing job. My paper makes complete sense and the writer followed my instructions. Best writer I've had.
Customer 454983, November 20th, 2021
Health Care
Thank you very much :)
Customer 455247, February 6th, 2022
Other
Great Writer. One of the best they have.
Customer 454983, March 7th, 2022
Other
Thank you
Customer 454677, March 18th, 2021
Other
Great writer
Customer 454983, February 11th, 2022
Health Care
I got an A. on this project thanks
Customer 453877, June 6th, 2020
11,595
Customer reviews in total
96%
Current satisfaction rate
3 pages
Average paper length
37%
Customers referred by a friend
OUR GIFT TO YOU
15% OFF your first order
Use a coupon FIRST15 and enjoy expert help with any task at the most affordable price.
Claim my 15% OFF Order in Chat
Live Chat+1(978) 822-0999EmailWhatsApp

Order your essay today and save 20% with the discount code GOLDEN