This past week, I learned about the mole and it’s relevant measurement molarity. It's a pretty large part of stoichiometry. A mole is the number of atomic mass units needed to make a gram of hydrogen. Molarity is a measurement of the number of moles in a liter, similar to density. We were introduced to the colorimeter, an instrument used to measure color absorption.
The colorimeter's operation was simple enough, but (as always) it was important to go over equipment operation procedures before class. The cubettes it uses require careful handling to get accurate results. First we use water to calibrate the colorimeter, by putting dihydrogen monoxide in a cubette and inserting the cubette into the colorimeter.
In this lab I learned how to conduct a lab (this being my first in this class) and how to operate a colorimeter. I learned how to format my lab journal and submit a flowing lab report. I learned how to properly compile various data into a graph in the specified format and how to come up with an equation for it. We used this equation to find molecular absorption later in the lab.
The colorimeter's operation was simple enough, but (as always) it was important to go over equipment operation procedures before class. The cubettes it uses require careful handling to get accurate results. First we use water to calibrate the colorimeter, by putting dihydrogen monoxide in a cubette and inserting the cubette into the colorimeter.
We began the lab with two popular sports drinks: Powerade and Gatorade. Both use the dye “Brilliant Blue FCF” (C37H34N2Na2O9S3) for color (providing experimental consistency), making the two ideal for a lab. To begin the lab, we measured the (635 hz) absorption of BBFCF in various mixtures of stock solution and hydrogen hydroxide.
The procedure was simple: fill cubettes with designated stock/H2O mixture and write down what the colorimeter put out.
Class Results (Stock/H2O):
Stock:H2O ratio
|
Concentration (M)
|
Absorption (test 1)
|
Absorption (test 2)
|
Absorption (test 3)
|
10:0
|
7.5
|
1.062
|
0.968
|
1.104
|
8:2
|
6.8
|
0.824
|
0.873
|
0.765
|
6:4
|
4.5
|
0.567
|
0.531
|
0.435
|
4:6
|
3.0
|
0.427
|
0.412
|
0.435
|
3:7
|
2.3
|
0.347
|
0.328
|
0.370
|
2:8
|
1.5
|
0.152
|
0.229
|
0.150
|
1:9
|
0.75
|
0.063
|
0.100
|
0.098
|
0:10
|
0
|
0
|
0
|
0
|
We then tested the Gatorade and Powerade (among 14 groups) in the colorimeter to see its absorbance.
Various Group Results (Power/Gatorade Absorption Results):
Powerade Absorption
|
Gatorade Absorption
|
0.405
|
0.140
|
0.374
|
0.140
|
0.366
|
0.125
|
0.386
|
0.141
|
0.312
|
0.147
|
0.389
|
0.138
|
We had to calculate the molarity of both sports drinks, using the methods presented to us earlier in the week. In my opinion, this was the most confusing part, I still don’t fully understand it. I hope to have this figured out before the test.
After all this was done, we compiled our data in our journals to find a few things. We put our data in a graphing program (or Excel) and got a formula:
y = 0.1367x - 0.0102
After all this was done, we compiled our data in our journals to find a few things. We put our data in a graphing program (or Excel) and got a formula:
y = 0.1367x - 0.0102
This would come to help us later in the experiment.
In this lab I learned how to conduct a lab (this being my first in this class) and how to operate a colorimeter. I learned how to format my lab journal and submit a flowing lab report. I learned how to properly compile various data into a graph in the specified format and how to come up with an equation for it. We used this equation to find molecular absorption later in the lab.
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