Spectrophotometry DQ
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Mackenzie Tijerina Section 617 Spring 2024 CHEM 120 Spectrophotometry: Pigments, light, and concentration Discussion Questions
Make sure that your responses to these discussion questions is legible, if your responses are illegible they will not receive credit. We suggest that you type your responses. Using the data that you collected and wrote in your lab notebook during lab, organize your data into the required tables or graphs. Make sure that you format the table properly, i.e. include a title and labels for your columns, etc. Also make sure your plots are properly formatted and clearly labeled. 1.
In a single table, tabulate your calibration curve data points. Make sure to include all proper labels and units for your solutions, concentrations, and Absorbance values. Also include your λ
max
value (2 points). Solution Concentration (M) Absorption at λ
max = 664.8 nm Stock Solution 3.00 x 10
-4 0.353 Dilution 1 (50% concentration) 1.50 x 10
-4 0.175 Dilution 2 (25% concentration) 7.50 x 10
-5
0.096 Dilution 3 (12.5% concentration) 3.75 x 10
-5 0.061 Table 1: Calibration curve data points.
2.
Attach plot for your calibration curve. Please format your graph including a title, axis-labels and units. Include your best fit line displaying the appropriate slope, y-intercept and R
2
value. (2 points). Chart 2: Calibration curve of the spinach solution using the λ
max = 664.8 nm comparing the absorption verses concentration.
3.
While doing the calibration curve plot for Spectrophotometry experiment, Zack and Mario had a conceptual discussion about how they should plot their data. Zach thinks that they should force the trendline for the absorbance vs concentration through the origin. On the other hand, Mario thinks (0,0) should be added. Is Zack or Mario correct? Using your data, explain why. Is adding (0,0) equivalent to forcing the trendline through the origine? Please provide your answer in paragraph form (6 points) I think that Mario would be right because with 0 absorption there should be 0 concentration. I think if we went with Zack’s idea this would be forcing the trendline through the origin because we see that the y intercept is (0, 0.01365) and this is the actual value that is given with the data we got from this experiment. y = 1,120.69565x + 0.01365
R² = 0.99829
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0
0.00005
0.0001
0.00015
0.0002
0.00025
0.0003
0.00035
Absorption Concentration (M) Calibration curve of Solutions (Absorbance vs. Concentration)
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The spectroscopic data in the table is generated with five solutions of known concentration.
Concentration (M)
0.0133
m=
0.0266
0.0532
0.106
0.213
Absorbance
0.1271
What is the intercept of the linear regression line?
0.08531
0.5388
1.069
Use a spreadsheet program, such as Microsoft Excel, to graph the data points and determine the equation of the best-fit line.
1.954
What is the slope of the linear regression line formed by these points?
M-1
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Could you please help me format this question, I've been stuck on it for some time now.
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Just part b!!!
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口
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Alchemy Lesson 20 & 21 Worksheet
Andres Carrill
Andres Carrillo - Alchemy Lessons 20 & 21 Worksheet
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Arial
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BIUA
E = E = EE E - E E X
1
2
3
4
.. 6 I 7 O 8 1 IC
5
AIV-20: Getting Connected (Writing lonic Compounds)
Part 1: Putting together lonic Compounds
lonic compound
Metal
Number of
cation
nonmetal
number of
anion
total
total charge = 0
valence
valence
number of
electrons
electrons
valence
electrons
NaF, sodium fluoride
Na
Na +
(+1)+(-1) = 0
F-
8.
MgO, magnesium oxide
Mg
02-
(+2) + (-2) = 0
MgCl2, magnesium
chloride
Mg
CI
7
16
(+2) + 2(-1) = 0
Ne, neon
Ne
8
BeF2, beryllium fluoride
Be
MgS, magnesium sulfide
CaCl,, calcium chloride
Na
Br
K
Se
Al
Al203, aluminum oxide
Al
Al
F
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PLEASE Answer within 20-30 minutes. Thank you!
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PART ONE: Preparation of FECNS* Solution
Prepare the two solutions in table 1 by accurately measuring the required volumes of distilled
water and CNS into two labeled test tubes. The absorbance of the solutions must be measured
soon after adding the Fe" solution from a buret.
TABLE 1
Fe
5 ml
5S mL
Solution
Distilled Water
CNS
2 mL
Total Volume
3 ml
2 ml
10 ml
3 mL
10 ml
In this part of the experiment you are to explore what the above quote means. As a
PRELIMINARY Exercise, formulate a hypothesis as to what would happen under each of the
following circumstances:
1. 1ml of 0.0020 M CNS' solution is added to the unused portion of
solution 1 in the test tube
2. One drop of 0.20 M CNS solution is added to the unused portion of
solution 2 in the test tube.
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+
terface/acellus_engine.htm?ClassID=1467683063
Use the data below to determine the
mass ratio of iron to oxygen for
compound 2.
Compound
1
2
Et
onal Academy of Science. All Rights Reserved.
Mass Fe
(grams)
15.55
20.98
[20:1
Enter the answer that belongs in the green box.
Iron Ratio Cmpd 2
Mass O
(grams)
4.45
9.02
Sh
Enter
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You work in a research organization that is looking for markers of various diseases that can be used as a diagnostic for the disease. It has been reported in the past that high levels of Cu are found in the sweat of people with cystic fibrosis. One of the research projects is focused on looking for high levels of Cu in samples that can be obtained non-invasively such as saliva, sweat, hair, nails, etc.
The lab will analyze large samples for Cu. What instrument would you recommend purchasing to support this work, Atomic absorption spectrophotometer or an inductively coupled plasma atomic spectrophotometer? Explain the basis for your decision.
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Write the corresponding letters to the following descriptions. Each proposal can be associated with 0 or
1 match and each letter is not necessarily associated with a proposal.
a. [Ar] 4s?
b. 1s 2s2p63s23p3
c. 1s2s2p2
d. [Ne] 3s23ps
e. [Ar] 4s23d10
f. 1s22s!
g. None of those answers
1. I am a halogen
2. I am a transition metal
3. I am alkaline
4. I have exactly 2 single electrons
5. I am the smallest of the atoms presented here
6. I have exactly 3 valence electrons
7.I am the most paramagnetic of the atoms presented here
8. I am the copper
9.I am isoelectronic with Ti2+
IF
cessibility: Good to go
IA
16
SIS
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From the data in Table 2.5, compute the concentration of the undiluted and diluted ovalbumin samples (make sure to account for the appropriate dilution factors, DF, in the computation).
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H J K L
Enter
V
B
N M
Shift
Chapter 2 An Introduction to the Chemistry of Life
37
SELF-QUIZ: TESTING YOUR KNOWLEDGE
1. Each atom has a nucleus made up of
р. 24.
2. In atoms, the number of protons is usually equal to the number
of
3. The atomic number of an atom is equal to the number of
7. Proteins and carbohydrates consist primarily of carbon,
hydrogen, and oxygen; these two molecules are types of
and neutrons.
-compounds. p. 31.
8. On the pH scale, a pH of is neutral; a solution with a pH
less than this is
this is
9. Chemicals like bicarbonate that resist pH change are called
р. 25.
and a solution with a pH greater than
р. 32,
in the nucleus. p. 26.
4 An alternative form of an atom is called an
differs in the number of neutrons in the nucleus. p. 26.
5. A bond formed between two atoms that share electrons is called
it
p. 33.
10. When water molecules dissociate, they form and
ions. p. 32.
bond. p. 28.
bonds form between oppositely charged atoms of
a(n)
polar covalent bonds of…
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a. What instrument was used to discover the structure of DNA?
b. What shape was expected from the instruments output? VWhy?
c. Who were the four main scientists involved in discovering the structure
of DNA?
d. What did you notice about the process of science represented in the
video? Name at least three things that you noticed.
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DELL
F4
F5
F6
F7
F8
F9
F10
F11
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88888:
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4.
6.
7
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7. You can see an MSDS below. Please answer the following questions related to the MSDS.
a) What is the name of this chemical?
b) What should you do if someone drinks the chemical?
c) Would this chemical catch on fire if it was exposed to flames?
d) If this chemical gets in your eye what should you do?
e) What color is this chemical?
f) What should you do if someone spills a small amount of the chemical?
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Using the data below, please create a calibration graph and determine the concentration of
the unknown sample.
Standard #1
Standard #2
Standard #3
Unknown sample
Concentration
1.5 x 10 M
2.0 x 103 M
2.5 x 10 M
?
Absorbance
0.61
0.80
0.98
0.72
a) 1.6 x 10 M
b) 1.8 x 10° M
c) 2.1 x 103M
d) 2.2 x 10 M
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Which one is it?
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When do you need to blank a spectrophotometer (Spec 20)?
After completing all data collection.
After the wavelength is changed.
Before running a set of samples.
Between each sample, even if the wavelength remains the same.
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Table 1. pH of water samples
Sample No.
Water Samples
pH
1
Tap water from household
6.59
2
Water from creek
7.35
3
Water from river
7.35
4
Unknown sample
7.00
Table 2. Absorbance of Samples
Table 3. Calibration Curve Data*
Sample No.
Absorbance
Absorbance
3-
Concentration of PO4
Ions, ppm
(1 pt each)
1
1.33
1.0
0.050
2
3.26
2.0
0.093
0.89
3.0
0.137
4
0.099
4.0
0.185
5.0
0.230
*Provided by the instructor
II. Graph
Determination of Phosphate Concentration
3-
1. Using Excel, plot the concentration of PO4* (x-axis) vs. absorbance (refer to Table 3) The olot
must show the equation of the best-fit (or trend) line of the graph. Attach the graph below
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Which one is it?
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If the standard addition intercept is the major source of uncertainty, find the uncertainty in the concentration of Sr in tooth enamel in parts per million. Find the 95% confidence interval for Sr in tooth enamel.
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Using the lab instructions and data table with data, please help me complete part 1 and 2 of my lab worksheet
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M
(2022-23) Unit 1: Mole Concept,
Unit 4 (FR) (Version 2) Assessment: Chemical Reactions
0.90
0.80-
0.70-
3 0.60
0.50-
0.40-
0.30-
Absorbance
2.
To spectrophotometrically determine the mass percent of cobalt in an ore containing cobalt and some inert
materials, solutions with known [Co²+] are prepared and the absorbance of each of the solutions is measured at
the wavelength of optimum absorbance. The data are used to create a calibration plot, shown below.
0.20
0.10-
0.00+
ㅏ
0.005
0.010 34 0.015
Concentration (M) .04
co₂
100-
pertoc
A 0.630 g sample of the ore is completely dissolved in concentrated HNO3(aq). The mixture is diluted with
water to a final volume of 50.00 mL. Assume that all the cobalt in the ore sample is converted to Co²+ (aq).
(a) What is the [Co²+] in the solution if the absorbance of a sample of the solution is 0.74 ?
(b) Calculate the number of moles of Co²+ (aq) in the 50.00 mL solution.
(c) Calculate the mass percent of Co in the 0.630 g sample of the ore.
Answer…
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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
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Please find standard de
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What safety rules did Andrew break?
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The light absorbance A of a molecule in solution is measured as a function of concentration [X].
[X]/M A
0 0
1.0 × 10–4 0.157
3.0 × 10–4 0.482
5.0 × 10–4 0.713
7.0 × 10–4 1.15
9.0 × 10–4 1.37
Use spreadsheet software to graph the data and calculate a best–fit linear trendline.
What is the equation of the line that best fits the data?
Question 5 options:
A = (1.55 × 103 M–1) [X] + (4.93 × 10–4)
A = (1.13 × 103 M–1) [X] + (2.52 × 10–4)
A = (9.94 × 102 M–1) [X] + (3.81 × 10–4)
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From the following data, calculate the concentration of the analyte in the sample read at 700 nm: Absorbance of unknown sample = 0.807 Absorbance of a 130 mg/dl standard = 0.234
Do not answer in image format.
Maintain accuracy and quality in your answer.
Answer completely.
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