Visible Spectra of Soft Drink

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The Visible Spectra and Concentration of Beverages

Purpose: The purpose of this experiment is twofold. The first part is designed to determine the origin of the color of a carbonated beverage. Be specific in your Purpose, which soda are you measuring? In the second part you will determine how much a sample of grape soda has been diluted, i.e. its concentration. Be specific, what is the sample ID for your unknown? Work as a team, but each person has their own unknown and part of the score depends on you accuracy.

Procedure: The spectrum of a carbonated beverage is obtained by measuring the absorbance of a sample of the beverage at different wavelengths using a spectrophotometer. This spectrum can then be related to the color of the beverage. In the second part, a calibration curve is prepared by measuring the absorbance of different standard concentrations of grape soda at a single wavelength. The absorbance of the unknown solution can then be measured at the same wavelength and compared to the calibration curve to determine its concentration.

Any waste in this experiment can be poured down the drain.

Part I: The Visible Spectrum of the Soda Pop.

Sample Preparation: Pour about 15-20 mL of the beverage into a beaker and stir to remove the carbonation. Dilute it to about 50% of its original concentration by pouring 10 mL into a graduated cylinder and add an equal volume of water. Stir.

Measuring the Visible Spectrum of the Carbonated Beverage:

Be sure the spectrophotometer is turned on and warms up for at least 5 minutes. Set the wavelength knob to 600 nm.
Using the zero adjust knob on the left side, set the needle to read 0% transmittance (%T) on the top of the meter. [Nothing should be in the sample compartment]. Be careful not to read the absorbance scale. Fill one cuvette with distilled water, wipe it with a tissue or paper towel, and insert it in the sample compartment with the line facing the front. Close the top. Use the...
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