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Archive for June, 2011

Thin Layer Chromatography and Paper Chromatography Abstract

In order to study distinct components of a mixture, they must be first separated individually. This is achieved through this lab by the technique called chromatography. We used two types of chromatography- thin layer and paper. They both involve a stationary phase which is either the paper or the TLC strip as well as a mobile phase, which could be one of two solvents used: iso-octane-acetone for TLC or ether acetone for paper. Chemicals in a sample separate due to their unique polarities. As a result, nonpolar substances move further than polar substances in this process.

Biological Molecules: Abstract

Throughout biology, structure determines function. As we begin to discover this theme, the lab completed serves as a prime example by testing for starch, reducing sugar, protein, and fat. On an atomic level, each of these molecules is composed of functional groups which distinguish to a certain extent a group’s chemical properties. As a result, these properties can be detected by specific tests such as an iodine test for starch, a Benedict’s test for reducing sugar, a Biuret test for protein, and a Sudan III test for fat. If amylose in starch is present, the effect is a deep, dark blue color when iodine is added because of starch’s unique coiled geometric arrangement. If none are present, then the color will remain orange or yellow. To test for the existence of a free aldehyde group, a Benedict’s test is conducted by heating a solution to form a precipitate that is blue, green, yellow, orange, or red in color; blue means there is no sugar present whereas the closer to brick-red the product is, the higher concentration of a reducing sugar is present. Consequently, a redox reaction occurs with the sugar oxidizing and the Benedict’s reagent reducing. The copper atoms in Biuret solution react with peptide bonds to produce a lavender or violet color, indicating the presence of proteins; otherwise, a light blue color appears if no protein is present. The Sudan III test reveals the nonpolar hydrocarbon groups remaining in the molecule by staining them red orange.

Spectrophotometry Lab Questions

  1. In graph (a), as the concentration increases, the absorbance increases

  1. In graph (b), as the concentration increases, the percent transmittance decreases

  1. If someone were to give you a solution of CuSo4, and to tell you that it had an absorbance of 0.1(or a percent transmittance of 90%), could you calculate the concentration of the solution? If you could how would you do it? Yes you could calculate the concentration of the solution by using the formula A=ebc. It states that A is absorbance (2 – log%T), e is the molar absorbtivity with units of L mol-1 cm -1, b is the path length of the sample – that is, the path length of the cuvette in which the sample is contained (cm), and c is the concentration of the compound in solution, expressed in mol L-1

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Haiku

Spring

The soft blowing wind

Creatures stirring from their nests

Fresh life sprouting up

 

Winter

Snow-covered tree limbs

Families in cozy homes

The gloomy dark sky