Chemiluminescence

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General Chemistry Laboratory 151

Chemiluminescence

Introduction:
The objective of tis experiment was to carry out systematic series of experiments in order to determine which chemicals and which ratios of chemicals produce the brightest light. Also, this experiment will determine which chemical produces the longest light. Chemiluminescence is the emission of light (luminescence), as the result of a chemical reaction. There may also be limited emission of heat. This occurs because the energy excites the product molecules into which it has been funneled. A molecule in this excited state either relaxes to the ground state, with the direct emission of light, or transfers its energy to a second molecule, which becomes the light emitter. Luminol (3-aminophthalhydrazide) is used in a commercially available portable device called the Luminox that measures minute concentrations (parts per billion) of the pollutant nitrogen dioxide in air. Luminol is also used frequently in laboratory demonstrations of the chemiluminescence phenomenon. Luminol-mediated chemiluminescence is the result of an oxidation reaction. The oxidation proceeds in two steps, which ultimately lead to the production of the aminophthalate anion in an excited state and the elimination of water and molecular nitrogen. The formation of the strong triple bond (N≡N) is a major factor in the release of energy in the form of light.

Luminol, a chemical widely used in the forensics community, reacts with iron to generate a luminescent reaction. When forensics teams want to determine whether or not traces of blood are at a crime scene, they can spray the site with Luminol to generate a reaction. It can also be used to check for traces of other reactants at a site, assuming that a chemical, which generates a chemiluminescent reaction, can be obtained. Some gas phase reactions also exhibit this property, so chemiluminescence can be used to check for traces of certain impurities in the air. Chemiluminescence can be observed in the glow of light sticks. It is also found in the glowing of fireflies and the light admitted by jellyfish and other sea creatures in the dark abyss of the sea.

This experiment involved two methods of systematically studying chemiluminescence; using a tad of powdered Luminol as well as a liquid solution of made with Luminol and sodium hydroxide. Bleach, sodium hydroxide, hydrochloric acid, hydrogen peroxide, DMSO and potassium solution (Our group only) where the chemicals used in the trial in error process. Heating and chilling certain chemicals where also used in determining which chemicals where the most vital, also the order in which they need to be added. Research was conducted in order to find other methods and chemical that could help ensure success. Each trial was preformed in individual wells with small amounts of Luminol (tad powder, 1ml liquid solution) to stretch the number of trials preformed. After achieving and recording the best trial the group must then be able to recreate that best trial. Results:

Table 1: Day 1
Trial| Luminol| Bleach| DMSO| 1ml NaOH| 1ml HCl| H2O2| Observations (1 sec)| A1 A6| Tad (1)| 5D (2)| 5D (3)| 6D (4)| | | Orange fizz | A2 B6| Tad (1)| 5D (3)| | | | 5D(2)| Blue Flash|

A3 C6| Tad (1)| 10D(4)| 10D(3)| | | 10D(2)| Blue Flash| A4 D6| Tad (1)| 10D(5)| 10D(4)| 10D (3)| | 10D(2)| Blue Flash| A5| Tad (1)| 10D(5)| 10D(4)| | 10D(3)| 10D(2)| Nothing| B5| Tad (1)| 10D(5)| | 10D(3)| 10D(2)| | Flash|

C5| Tad (1)| 10D(4)| 10D(3)| 10D(2)| | | Blue Flash| D5| Tad (1)| 10D(2)| | | 10D(3)| 10D(4)| Nothing|
A4| Tad (1)| 10D(2)| | 10D(3)| | | Nothing|
B4| Tad (1)| 10D(4)| | 10D(2)| | 10D(3)| Blue/Green Flash | C4| Tad (1)| 10D(4)| | 5D(2)| | 10D(3)| Blue/Green Flash| D4| Tad (1)| | 5D (3) | | 5D(2)| | Nothing|
B1| Tad (1)| 5D(4)| | | 20D(2)| 5D(3)| Nothing|
C3| Tad (1)| 5D(2)|...
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