Paper, Thin Layer, and Liquid Chromatography AP Chemistry Lab.
Paper, Thin Layer, and Liquid Chromatography
I. Purpose: The purpose of the experiment is to use four different methods of chromatography: paper (circle and strip), thin layer, and liquid chromatography. The purpose is to see the separation of dyes and to determine the ions present in an unknown sample (sample D for paper and sample 4 for thin layer).
II. Pre-Lab Questions:
1. What does the technique of chromatography allow us to do? Chromatography allows us to observe the separation of the components of a mixture and to identify compounds.
2. What is the meaning and utility of an Rf value? What would you expect to influence and Rf value? The Rf value is the ratio of the distance traveled by a compound to the distance traveled by the solvent. The Rf value is unique depending on the compound and solvent.
3. What are the developing reactions that allow the identification of Ni2+ and Cu2+? The developing reactions for the Ni2+ was using the dimethylglyoxime to form a red color and Cu2+ is the reaction with the ammonium hydroxide to form a deep blue color.
4. What forces cause the eluting solution to move along the chromatographic support material? Capillary action causes the solution to move along the chromatographic support material. The solvent and various components of the mixture each travel at different speeds along the paper.
5. Why should the solvent front be marked immediately? The solvent front should be marked immediately because it evaporates quickly.
6. If the solvent front is 66 mm and the ring front of an unknown is 48 mm, what is the Rf value? The Rf value is 0.7273.