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CHEM 237L LAB REPORT - ACCURATE AND PRECISE MEASUREMENT OF VOLUME SUBMITTED APRIL
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CHEM 237L LAB REPORT - ACCURATE AND PRECISE MEASUREMENT OF VOLUME SUBMITTED APRIL
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CHEM 237LLAB
REPORT
2024
NAME: Allan Goldbert
STUDENT ID NUMBER: 202478901
PARTNER’S NAME: Shantelle Belle
SECTION NUMBER: 002
LOCKER NUMBER: C-301
EXPERIMENT TITLE: Accurate and precise measurement of volume
DATE EXPERIMENT PERFORMED: April 10, 2023
DATE REPORT DUE: April 24, 2023
DATE REPORT SUBMITTED: April 24, 2023
GRADE: A+
Lab Submission Declaration:
I, (the undersigned), declare that this submission is my own work and has not been copied from any other
source without attribution, that this submission is not the result of collaborative effort with
another individual(s) and that this report is being submitted for the first-time for academic evaluation.
I acknowledge that severe penalties exist for any copying of material from other sources without attribution,
for excessive collaboration and for repeat submissions, including a mark of zero (0) for this course.
,Results
Data and calculations
Table 1: Absorbance of serial dilutions of Coomassie blue at 595nm
Solution Dilution Concentration Total volume Contents Absorbance Colour intensity
(mg/mL) (mL) (at 595nm) (relative)
Coomassie blue Stock 0.5 - - - -
1 1/5 stock 0.1 10 2mL CB, 8mL H2O 2.7511 ++++++
2 1/10 #1 0.01 2 1mL #1, 9mL H2O 0.4156 +++++
4/5 4/5 #2 0.008 2 1.6Ml #2, 0.4Ml H2O 0.2828 ++++
3/5 3/5 #2 0.006 2 1.2Ml #2, 0.8Ml H2O 0.2155 +++
2/5 2/5 #2 0.004 2 0.8Ml #2, 1.2Ml H2O 0.1393 ++
1/5 1/5 #2 0.002 2 0.4Ml #2, 1.6Ml H2O 0.0661 +
Table 2: Volume measurement by mass with average/deviation
Volume setting Mass Average mass Deviation Average deviation
Pipettor
(Ul) (g) (g) |g| (g)
0.7911 0.0013
800 0.7933 0.7924 0.0009 0.00087
Blue 0.7928 0.0004
(1000 Ul) 0.2951 0.0010
300 0.2923 0.2941 0.0018 0.00117
0.2948 0.0007
0.0781 0.0007
80 0.0792 0.0788 0.0004 0.00050
Yellow 0.0792 0.0004
(100Ul) 0.0292 0.0005
30 0.0300 0.0297 0.0003 0.00033
0.0299 0.0002
Table 4: Arbitrary slope with varying path length so au(mg/mL)-1 auM-1cm-1
Original slope Molar mass l = 1cm l = 2cm l = 4cm
42.125 mL/mg 854g/mol 35975 auM-1cm-1 17987 auM-1cm-1 8994 auM-1cm-1
Table 3: Sample calculations
Average mass Average = Sum of masses / N
= (0.0781 + 0.0792 + 0.0792) / 3
= 0.0788
Average deviation Average deviation = Sum of |deviations| / N
= ( |-0.0013| + |0.0009| + |0.0004|)/3
= 0.00087
Dilution C1V1 = C2V2
C1V1 = (0.5mg/Ml) (2Ml) / 10Ml
C1V1 = 0.1mg/Ml
Arbitrary slope Concentration / Molar mass where
mL x g x 1L x 1000mg therefore
mg mol 1000mL 1g
42.125 mL/mg x 854 g/mol = 35975auM-1
, Graphical data
Absorbance as a function of concentration at 595nm
0.45
y = 42.125x - 0.0289
0.4
R² = 0.9811
0.35
0.3
Absorbance
0.25
0.2
0.15
0.1
0.05
0
0 0.002 0.004 0.006 0.008 0.01 0.012
Concentration (mg/mL)
Questions
1: What trend did you see between the colour intensity and the absorbance value recorded? What can you
conclude from this observation?
The more intense the colour, the higher the absorbance value recorded. One can conclude from this observation that Beer
Lambert Law (Abs = ECl) holds true where absorbance is directly proportional with the sample concentration.
2: What is the slope value for the line of best fit from your graph?
The slope value is 42.125 au(mg/mL)-1.
3: For the slope value obtained from your plot, convert the mg/mL to M-1. Use the molar mass of 854g/mol for
Coomassie Brilliant Blue G-250. Your final slope value should be in units of M-1 or arbitrary units M-1. What does
this slope value mean with respect to the absorbance property of Coomassie Blue and the Beer-Lambert law
equation assuming that the cuvette used in the lab has a 1.0cm path length?
The arbitrary slope is 35975auM-1. The absorbance properties of the Coomassie Blue molecules depend on the mobility
of its chromophores where higher the molar absorptivity, the higher the slope. Beer Lambert’s law confirms this as it
states that absorbance is directly proportional to concentration and path length (as observed in question 1).
4: How do you expect the slope value to change if you used a cuvette with a path length of 4.0cm? What if the path
length was 2.0mm? Give a brief explanation to your reasoning
As path length increases, slope decreases because absorbance is directly proportional to path length according to the Beer
Lambert Law (Abs = ECl) but this slope requires path length to be in cm instead of be cm-1, therefore causing a division
by the path length (decrease) rather than a multiplication (increase).
Summary
Identify the Beer-Lambert relationships regarding absorption and concentration, determine the molar extinction
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