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Fantastic Four Cola Lab

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Anurag Khandavalli

on 3 October 2013

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Transcript of Fantastic Four Cola Lab

Spectrometer 20
Spectrometer 20 (Spec 20) - a scientific instrument used to measure light absorbance and percentage transmittance at certain wave length
Four Basic Components:
Wavelength control knob
Light control knob
Power knob
Sample holder
Warm up Spec 20
Calibration required before every test at different wavelength
Take care not to touch test tube to ensure better results
Experimental Design
3 Parts of Experimental Design
Learning how to proficiently use a Spec 20 and determining analytical wavelength
Using different molarities of a substance to create a calibration curve
To analyze level of phosphoric content in various cola samples
The results of the data indicate that the coke is the cola sample that has the highest concentration of phosphoric acid
The discrepancies in the data stem from human error in measuring, and some degree of mechanical error from the Spec 20.
Cola Analysis Lab
Understand the Spec 20
Read manual and understand various tenets. (transmittance knobs, blank tubes, etc.
Understand Relationship between color and wavelength
KMNO4 and Food Coloring
Understand Relationship between absorbance and concentration
Test and Check
Determine Phosphoric Acid content in Colas
3 Different solutions of Cola and AVM
Difference of Molarity and Wavelength and Effect on % T and Abs.
K2HPO4 + AVM Effects on % T and Absorbance
Table 1: Difference of Color and Wavelength and Effect on % T and Absorbance.
For All Dilution Calculations: Use (M1)(V1) = (M2)(V2)

0.1 M of K2HPO4 was diluted to 0.0002 M in two steps.
First 5 mL of the original concentration was diluted to 100 mL of 0.005 M concentration
Then 4 mL of the 0.005 M concentration was diluted to 100 mL of 0.0002 M.

Next 10 mL of 0.0002 M K2HPO4 and 10 mL of the Ammonium Vanadomolyvdate (AVM) were combined and the solution was tested in the Spec 20.
The calculations between 350 and 550 nm are shown in Table 3.
At a wavelength of 350 the Spec 20 was unresponsive, so the tests began at 375 nm.
In between each test, the Spec 20 was checked to make sure it was still at the right percent transmittance by using a “blank” composed of 10 mL H2O and 5 mL of AVM.

After the previous test, the analytical wavelength was found to be 400 nm.
For the next test the molarity was adjusted and the wavelength was kept at 400 nm.
The molarity was adjusted by trial and error in order to find solutions that would give percent transmittance between 15% - 85%.
However, in order to achieve a lower percent transmittance the initial volume and concentration would have had to be changed too, which was not an option for the group.

Gaining Proficiency
Yellow and blue food coloring drops were added to 100 mL of water
Solution of .004 M KMnO4 diluted to .001 M KMnO4
Solutions tested for absorbency and transmittance levels at increments of 50 nm (350 - 650)
Wavelength that yielded highest level of absorbency found to be analytical wavelength.
Calibration Curve
Solution of .01 M K2HPO4 diluted to .0002 M
5 mL of K2HPO4 mixed with 5 mL ammonium vanadomolybdate (AVM)
Analytical wavelength determined to be 400 nm
Different solutions of various molarities of K2HPO4 created from solution of 0.0002 M
5 mL of solution of varying molarity mixed with 5 mL of AVM
Different molarities absorbance and transmittance graphed against molarity(calibration curve)
Determining Cola Content
Three solutions of Cola heated for twenty minutes to get rid of carbonation
5 mL of each Cola solution mixed with 5 mL of cola
Solution placed in Spec 20 to determine absorbance
Absorbance used to find concentration of phosphate by using the calibration curve
Concentration of Phosphate by Cola Proportion
As indicated by the results, the normal Coke had the highest concentration of phosphate.
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