Introduction:

The goal of this experiment is to properly measure the absorption spectra of a series of solutions, by properly using a spectrometer, and by using a color chart to generate a rough measurement.

I hypothesize that by properly using the spectrometer, and cleaning the cuvettes beforehand, that one should be able to generate a graph showing the absorption spectra of the solutions analyzed.

Equipment:

• Data Collection System
• Spectrometer
• Cuvettes (6)
• Sensor Extension Cable
• Test Tubes (6)
• Graduated Cylinder, 10-mL
• 0.1 M Iron(III) Chloride, 10mL
• 0.1 M Copper(II) Chloride, 10mL
• 0.1 M Cobalt(II) Chloride, 10mL
• 0.1 M Nickel(II) Chloride, 10mL
• 0.1 M Sodium Chloride, 10mL
• Color Chart
• Wash Bottle with Deionized Water
• Marker

Method:

• Gathered Equipment and Materials. Set up data collection system, linked it to the spectrometer, and turned on the computer. 
• Cleaned test tubes and cuvettes. Added 10 mL of each solution to each test tube, the 6th of which received water. Filled each cuvette 2/3rds of the way with the solutions, and the 6th with water.
• Inserted each cuvette one at a time. Recorded absorbance of each solution, one at a time, saving each before moving on to the next. Linked to computer, and generated graph of absorption spectra for all solutions. Printed graph. Saved Data.
• Disposed of solutions in designated containers. Cleaned all test tubes and cuvettes, before returning all equipment to its point of origin.

Data Analysis:

(Note: All wavelengths are measured in nanometers, unless specified otherwise.)

From this, we can gather that the wavelength ranges absorbed by the various solutions to be as follows: Cobalt(II) Chloride (400-550 nm), Nickel(II) Chloride (410-480 nm, 610-800 nm), Iron(III) Chloride (380-570 nm), Copper(II) Chloride (670-900 nm), Sodium Chloride (none), and Water (also none).

Conclusion:

The goal of this experiment is to properly measure the absorption spectra of a series of solutions, by properly using a spectrometer, and by using a color chart to generate a rough measurement.

(Calculation of error not possible due to lack of accepted absorption values for the solutions measured.)

The wavelength ranges absorbed by the various solutions are as follows: Cobalt(II) Chloride (400-550 nm), Nickel(II) Chloride (410-480 nm, 610-800 nm), Iron(III) Chloride (380-570 nm), Copper(II) Chloride (670-900 nm), Sodium Chloride (none), and Water (also none).

Possible sources of error include:

• Failure to properly clean the cuvettes.
• Contamination of cuvettes while handling them.
• Contamination of solutions used, thus altering them from their formula and concentration.
• Contamination or other error, relating to the spectrometer (such as smudging the lens).
• Failure to generate a proper graph, due to lack of knowledge of the directions.
• Human error is always in effect, given that the laboratory does not function under ideal conditions. As such, there is always the possibility of inaccuracies with measurement, perception of measurement, inaccuracies of equipment, and other such errors. (However, this is not likely to be the sole cause of the inaccuracies within this experiment, though it may contribute to it.)

Possible improvements to this experiment include testing each solution multiple times (to average out their absorption spectra), using crystal cuvettes and using a more accurate spectrometer.