Chromatography - Experiment 1 Revision 1.1 Paper...

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Experiment 1 Revision 1.1 Paper Chromatography of a Metal Cation Mixture To learn about the separation of substances. To learn about the separation technique of chromatography. To learn how to use properties of known substances to identify unknown substances. In this laboratory exercise we will separate and identify the cations in an aqueous mixture that possibly contains Fe 3+ , Ni 2+ or Cu 2+ salts. The separation will be achieved using Paper Chromatography. Identification of the cations will be affected by simultaneously running separate solutions, each containing a single salt of these ions, through the chromatographic system and comparing the results against those of the unknown solution. Separation of substances is a key component in most chemical processes. Reaction products need to be separated from associated by-products, complex natural systems need to be separated to obtain a desired component, etc. Thus, in some sense, the science of chemistry is really the science of separations. And, over the years, chemists have developed an enormous array of techniques for the separation of substances. In 1906 the Russian scientist Mikhail Semenovich Tswett reported separating the different colored pigments of plant leaves by passing a liquid extract of the leaves through a column of calcium carbonate (think powdered chalk). He coined the term chromatography, from the Greek words χρώμα (chroma or color”) and γραφειν (graphein or “to write"), to describe this process. Presently, chromatography is the general name applied to a series of separation methods that employ a system with two phases of matter; a mobile phase and a stationary phase. The separation process occurs because the components of the mixture have different affinities for the two phases and thus move through the system at different rates. A component with a high affinity for the stationary phase moves more slowly, whereas one with a high affinity for the mobile phase moves more rapidly. Paper chromatography, probably the simplest chromatographic system, employs a strip of porous paper for the stationary phase. A drop of the mixture to be separated is placed on the paper, which is then dipped into a liquid, the mobile phase. The liquid travels up the paper as though it were a wick. The separation occurs as the liquid moves along the paper, carrying along with it, most rapidly, those components with a low affinity for the paper and leaving behind those with a high affinity for the paper.
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Chromatography - Experiment 1 Revision 1.1 Paper...

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