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Relationship Between Index of Refraction and Concentration of Trihexylmethylammonium. An Experiment by the Group “Isn’t It Ionic?” Melissa Castillo, Tony Roerig, Amanda Tucek, and Marty Walsh April 2006. What is the Refractive Index?. Light bends in different mediums
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Relationship Between Index of Refraction and Concentration of Trihexylmethylammonium An Experiment by the Group “Isn’t It Ionic?” Melissa Castillo, Tony Roerig, Amanda Tucek, and Marty Walsh April 2006
What is the Refractive Index? • Light bends in different mediums • Snell’s Law Gives Equation for Refractivity: n1sin(i) = n2sin(r)
What is the Refractive Index? • Each substance has its own unique index of refraction
What is the Refractive Index? • If the RI for two substances is the same, they will be visually indistinguishable
How does Solution Concentration Influence the Index of Refraction in Ionic Liquids? Experimental Question:
How does Concentration Relate to Refraction? • Beers Law relates concentration to absorbance • As demonstrated in our previous lab, absorbance is directly proportional to concentration • ? What happens to refraction? Is it the same?
Testing Procedures • Use Chemistry handbooks to look up RI values for known liquid • Measure the RI values for dilutions of glycerol • Graph the relationship: [solvent] vs. RI • Measure the RI values for ionic liquid • Compare the behavior of IL vs. glycerol
Results: Known Substance • [Glycerol] and RI have a direct linear relationship • It is important to dilute the substance being tested with something that has a different RI value
Results: Trihexylmethylammonium • [Trihex] and RI also display a direct linear relationship
Conclusion • Trihexylmethylammonium is consistent with other solutions in that the amount of refraction is directly proportional to the solution concentration • A question for further study is: Do all Ionic Liquids behave in this fashion?