Pre-lab 5 - Beer's law
.pdf
keyboard_arrow_up
School
Seton Hall University *
*We aren’t endorsed by this school
Course
109
Subject
Chemistry
Date
Feb 20, 2024
Type
Pages
2
Uploaded by Alan040802
74
·
Quantitative General Chemistry Lab Manual
Lab 5: Pre-Lab Assignment
Name:
Section:
1. Assuming Allura Red, molar mass 496.42 g/mol, has a molar absorptivity of about 25,000
cm
−
1
M
−
1
at 500 nm, what mass of it will you need to create 100. mL of a solution that
has an absorbance of 1.0 in a 1.0 cm cuvette?
2. Will you be able to accurately measure that mass using a top-loading balance? Why or
why not?
3. What about with an analytical balance? Why or why not?
Lab 5: Quantitative Analysis Using Beer’s Law
·
75
4. Considering this amount you would have to weigh out for a dilution to 100 mL in volu-
metric glassware, propose another volume to dilute to that might be easier to execute. Is
this volume practical considering you only need
∼
1 mL of the final solution to check its
absorbance at 500 nm?
5. If you think the molar absorptivity of this food dye is representative of most dyes at their
respective
λ
max
, do you think most dyes can be accurately weighed as a dry powder and
diluted in a single step using common volumetric glassware to achieve an absorbance value
in the linear range of a spectrophotometer? Would your answer be different if you were
aiming for an absorbance value of 0.1 instead of 1.0?
As part of your notebook preparation, create a diagram similar to Figure 5.4 for creating
the absorbance 1.0 solution of Allura Red based on your answers to the pre-lab assignment.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Related Questions
A. Copper sulfate pentahydrate is often used to teach students about Beer’s Law by making a standard curve (linear regression). The bright blue color of the solution has a peak absorbance in the red range of the electromagnetic spectrum. The absorbance value is proportional to concentration. How many grams of CuSO4 5H2O to make up 250 mL of a 0.2 M stock of this solution?
B. Using M1V1 = M2V2 how many mL would a student need to measure out in graduated cylinder to make up a 50 mL (V2) solution of 0.1M, 0.05 M, 0.025M 0.0125M solutions for a standard curve at the peak wavelenth for this compound?
arrow_forward
A. Copper sulfate pentahydrate is often used to teach students about Beer’s Law by making a standard curve (linear regression). The bright blue color of the solution has a peak absorbance in the red range of the electromagnetic spectrum. The absorbance value is proportional to concentration. How many grams of CuSO4 5H2O to make up 250 mL of a 0.2 M stock of this solution?
B. Using M1V1 = M2V2 how many mL would a student need to measure out in graduated cylinder to make up a 50 mL (V2) solution of 0.1M, 0.05 M, 0.025M 0.0125M solutions for a standard curve at the peak wavelenth for this compound?
I need help with part B of this question.
arrow_forward
A direct ELISA experiment was done to determine the amount of protein present in a sample. A standard curve was prepared by plotting log Absorbance versus log concentration of protein in (ng/mL). The equation of the line is Y= 0.895 X -1.25. If an unknown protein shows an absorbance of 1.23. Calculate the concentration of this protein in the sample in (ng/mL).
arrow_forward
Q)A histidine solution with a concentration of C = 60.5 mg/L has an absorbance of 0.794 when the light path length is 1.0 cm. Note that the molecular mass of tryptophan is 155.15 g/mol. 1-Calculate the molar absorbance of a histidine solution expressed as L.mol 1.cm-1.
2-Description of the preparation of 100 mL of a 15.0 ppm histidine solution mentioned above
arrow_forward
If a solution has an absorbance of 2 you can be certain that
the solution is highly diluted and needs to be concentrated
all the statements are correct
this is a reliable absorbance and downstream analysis can be done
the solution is highly concentrated and needs dilution
arrow_forward
23. How do you set up and solve absorbance problems like this?
arrow_forward
Can you help me on questions 2 AND 3
arrow_forward
Data complete
arrow_forward
What does a refractometer reading of 2 mean when distilling ethanol?
arrow_forward
22. To test a spectrophotometer's accuracy, a solution of 60.06 ppm K2Cr2O7 is
prepared and analyzed. This solution has an expected absorbance of 0.641 at
350.0 nm. Several aliquots of the solution produce the following absorbance
values.
0.640 0.638 0.640 0.639 0.640 0.639 0.638
is there any significant difference between the experimental mean and the expected
value at a 99.9% confidence level?
Yes because tcal>tcritical
Yes because tcaltcritical
No because tcal
arrow_forward
Which statement is true?
Statement 1: In Thin Layer Chromatography (TLC), the polar compounds will have a greater Rf value compared to that of non-polar compounds.Statement 2: The stationary phase in TLC is polar.
arrow_forward
GMU QUESTION 7
An ethanol solution of 3.5 mg/100 ml of compound Y (150.0 g/mol) in a 1.00 cm quartz cell has an absorbance (A) of 0.972 at Amax-235
nm. What is its molar extinction coefficient? Report your answer to the correct number of significant figures. Do not include units in your
answer.OGMU 2020
arrow_forward
Table II
Cuvette #
Concentration
Absorbance
0.50 M
1
1.049
2
0.40 M
0.926
3
0.20 M
0.740
0.298
4
0.10 M
5
0.05 M
0.202
Unknown # 9
0.427
Unknown # 10
7
0.646
Blank (DI water)
0
1. If Beer's Law is valid, the value of "E" should be constant. Use A = E*C*L or E=
A/(E*L) and the data from Table II to calculate values of E for the five solutions below
The value of L is normally 1 cm so E = A/C in this experiment.
Table III
Solution #
Calculated Values of E
1
2
3
4
5
arrow_forward
AP Questions // Questions 10 - 11) A student creates four solutions with varying
concentration of FeSCN2 and gathers the following data at 298 K using a spectrophotometer
calibrated to 460 nm:
[FESCN]
Absorbance
1.1 x 10-4 M
0.076
1.6 x 10-4 M
0.112
2.2 x 10-4 M
0.167
2.5 x 10-4 M
0.199
On the axis below, create a Beer's Law calibration plot for [FESCN2*]. Draw a best-fit line
through your data points.
arrow_forward
25. How would you set up and solve concentration problems like this which involve absorbance?
arrow_forward
Please do questions 2 and 3. Dont do it all, just show me how to solve one and I will do the rest.
arrow_forward
PLEASE Answer within 20-30 minutes. Thank you!
arrow_forward
How would I do 2? the concentration iron is 1.85mg/vitamin tablet, and the absorbance at 508nm is 0.37
arrow_forward
Using the following data, if an unknown solution of Orange Dye X had a measured absorbance of 0.345, what is the concentration Orange Dye X in the solution?
Concentration (mM)
Absorbance
0.005
0.143
0.010
0.285
0.015
0.428
0.020
0.570
arrow_forward
Given the following standard curve of Absorbance vs Concentration (mM), what in the concentration of Aspirin if the absorbance is 0.822?
arrow_forward
Can someone help me interpret this data to be put on my research paper? This is the absorbance spectrum fo Sulfamethoxazole (sulfonamide antibiotic). Thank you so much!
arrow_forward
A solution prepared by dissolving 25.8 mg of benzene (78.11 g/mol) in hexane (86.16 g/mol) and diluting to 250 mL had an
absorption peak at 256 nm and an absorbance of 0.266 in a 1.000-cm cell. What is the concentration of benzene solution?
O 1.20x10-3 M
O 1.32x10-3 M
O 1.32 M
O 1.20 M
arrow_forward
Conclusion 5: You are tasked with analyzing a suspiciously pink sample of drinking water to establish if it has unsavory levels of MnO4-contamination. It has an absorbance of 0.83 at 544 nm when measured in a cuvette that is 1 cm across.
Using the equation of your trend line from Plot 4, determine the concentration of KMnO4 in moles/liter.
Convert this concentration to grams of manganese/liter and compare it to the EPA guideline above.
Trandline is Absorbtion = 2000(Concentration KMnO4) (Y=Mx)
arrow_forward
A series of six solutions was prepared at the given concentrations.
Sample
AB C
D
E
F
Concentration (mM)
50 100 | 150 | 200 300 400
The absorbance of each solution was then measured using a colorimeter.
Sample
A
B
C
D
E
F
Absorbance
0.25
0.50
0.75
1.00
1.50
2.00
What is the concentration of the solution with an absorbance of 1.50?
C =
mM
arrow_forward
Chemistry Question
arrow_forward
4. An ethanol solution of p-aminosalicylic acid has a molar absorptivity of 1.6 x 10ʻL
mol"cm at a wavelength of 284 nm. Calculate the absorbance of a 4.8 x 10°M
solution in a 1.000 cm cuvette at this wavelength.
arrow_forward
SEE MORE QUESTIONS
Recommended textbooks for you
Chemistry & Chemical Reactivity
Chemistry
ISBN:9781133949640
Author:John C. Kotz, Paul M. Treichel, John Townsend, David Treichel
Publisher:Cengage Learning
Related Questions
- A. Copper sulfate pentahydrate is often used to teach students about Beer’s Law by making a standard curve (linear regression). The bright blue color of the solution has a peak absorbance in the red range of the electromagnetic spectrum. The absorbance value is proportional to concentration. How many grams of CuSO4 5H2O to make up 250 mL of a 0.2 M stock of this solution? B. Using M1V1 = M2V2 how many mL would a student need to measure out in graduated cylinder to make up a 50 mL (V2) solution of 0.1M, 0.05 M, 0.025M 0.0125M solutions for a standard curve at the peak wavelenth for this compound?arrow_forwardA. Copper sulfate pentahydrate is often used to teach students about Beer’s Law by making a standard curve (linear regression). The bright blue color of the solution has a peak absorbance in the red range of the electromagnetic spectrum. The absorbance value is proportional to concentration. How many grams of CuSO4 5H2O to make up 250 mL of a 0.2 M stock of this solution? B. Using M1V1 = M2V2 how many mL would a student need to measure out in graduated cylinder to make up a 50 mL (V2) solution of 0.1M, 0.05 M, 0.025M 0.0125M solutions for a standard curve at the peak wavelenth for this compound? I need help with part B of this question.arrow_forwardA direct ELISA experiment was done to determine the amount of protein present in a sample. A standard curve was prepared by plotting log Absorbance versus log concentration of protein in (ng/mL). The equation of the line is Y= 0.895 X -1.25. If an unknown protein shows an absorbance of 1.23. Calculate the concentration of this protein in the sample in (ng/mL).arrow_forward
- Q)A histidine solution with a concentration of C = 60.5 mg/L has an absorbance of 0.794 when the light path length is 1.0 cm. Note that the molecular mass of tryptophan is 155.15 g/mol. 1-Calculate the molar absorbance of a histidine solution expressed as L.mol 1.cm-1. 2-Description of the preparation of 100 mL of a 15.0 ppm histidine solution mentioned abovearrow_forwardIf a solution has an absorbance of 2 you can be certain that the solution is highly diluted and needs to be concentrated all the statements are correct this is a reliable absorbance and downstream analysis can be done the solution is highly concentrated and needs dilutionarrow_forward23. How do you set up and solve absorbance problems like this?arrow_forward
- 22. To test a spectrophotometer's accuracy, a solution of 60.06 ppm K2Cr2O7 is prepared and analyzed. This solution has an expected absorbance of 0.641 at 350.0 nm. Several aliquots of the solution produce the following absorbance values. 0.640 0.638 0.640 0.639 0.640 0.639 0.638 is there any significant difference between the experimental mean and the expected value at a 99.9% confidence level? Yes because tcal>tcritical Yes because tcaltcritical No because tcalarrow_forwardWhich statement is true? Statement 1: In Thin Layer Chromatography (TLC), the polar compounds will have a greater Rf value compared to that of non-polar compounds.Statement 2: The stationary phase in TLC is polar.arrow_forwardGMU QUESTION 7 An ethanol solution of 3.5 mg/100 ml of compound Y (150.0 g/mol) in a 1.00 cm quartz cell has an absorbance (A) of 0.972 at Amax-235 nm. What is its molar extinction coefficient? Report your answer to the correct number of significant figures. Do not include units in your answer.OGMU 2020arrow_forwardarrow_back_iosSEE MORE QUESTIONSarrow_forward_ios
Recommended textbooks for you
- Chemistry & Chemical ReactivityChemistryISBN:9781133949640Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage Learning
Chemistry & Chemical Reactivity
Chemistry
ISBN:9781133949640
Author:John C. Kotz, Paul M. Treichel, John Townsend, David Treichel
Publisher:Cengage Learning