Lab 6-Colorimetry - absorbance increases The opposite is...

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Roshni Sheth CH 116-M3 Partners: Chris Suda, Kaity Brown October 21, 2009 Colorimetry 1. The Spectrophotometer The spectrophotometer was set to measure absorbance at 560 nm. The spectrophotometer is an instrument that has a hood that can be lifted to reveal a slot where the cuvet can be placed. It measures the intensity of how much light passes through a cuvet of a particular solution compared to a cuvet of a blank solution. Light is measured as a function of color, the wavelength. 2. Absorbancies Concentration (M) Absorbance Stock 0.02 0.6743 1 st 0.01 0.3046 2nd 0.007 0.2072 3rd 0.0012 0.0378 blank NH 3 0.0000 unknown unknown 1.8153 For the copper solutions (stock, 1 st , 2 nd , and 3 rd ), the concentration and absorbance are directly related. As the concentration of copper in the solution increases, the absorbance increases. The NH 3 , or the blank, has an absorbance of 0.0000 because it is colorless and used to dilute the copper solutions.
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3. The Calibration Curve Concentration and absorbance have a direct relationship. As concentration increases,
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Unformatted text preview: absorbance increases. The opposite is also true: as concentration decreases, absorbance decreases. Based on the graph, this relationship is acceptable because the R 2 value is 0.9962, which is only 0.0038 from being a true direct relationship of an R 2 value of 1. This means that the graph is accurate. 4. The Preparation of the Complex Ion As ammonia is added to the copper solution, the solution transforms into a deep royal blue color. As the solution is diluted and the concentration decreases, the shade of blue of the solution becomes lighter and lighter. 5. Concentration of the “Unknown” Using the equation from the graph, the concentration (M) of the unknown is approximately 0.0537. The standard deviation of the copper solutions with the unknown is ± 0.2590. The standard deviation of just the copper solutions (stock, 1 st , 2 nd , and 3 rd ) is ± 0.26916....
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This note was uploaded on 06/28/2011 for the course CH 116 taught by Professor March during the Fall '09 term at University of Alabama at Birmingham.

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Lab 6-Colorimetry - absorbance increases The opposite is...

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