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State the principle on which all chromatographic separation techniques are based - Leaving Cert Chemistry - Question c - 2005
Question c
State the principle on which all chromatographic separation techniques are based. Describe with the aid of clearly labelled diagrams how you could carry out an expe... show full transcript
Worked Solution & Example Answer:State the principle on which all chromatographic separation techniques are based - Leaving Cert Chemistry - Question c - 2005
Step 1
State the principle on which all chromatographic separation techniques are based.
Answer
Chromatographic separation techniques are based on the selective adsorbance of substances on a stationary phase and their relative affinities for a mobile phase. The principle relies on the partitioning of components between a stationary phase, which is fixed in place, and a mobile phase, which moves through or along the stationary phase. This allows for the separation of components based on their different interactions with these phases.
Step 2
Describe with the aid of clearly labelled diagrams how you could carry out an experiment to separate a mixture of dyes (or indicators) using paper chromatography.
Answer
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Setup: Prepare a chromatography setup with a chromatography plate (paper) and a suitable solvent.
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Application of the Mixture: Use a dropper to place small spots of the dye mixture about 2 cm from the bottom of the paper strip.
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Development: Immerse the bottom of the paper strip in the solvent, allowing it to ascend by capillary action. Ensure that the solvent level is below the spots of dye.
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Observation: After a predetermined time, remove the paper and mark the solvent front. Observe the different colored bands that indicate the separation of dyes, which can be further analyzed.
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Labeling: The paper should be clearly labeled with the position of the initial dye spots and the resultant bands of colors for clarity.
Step 3
Describe with the aid of clearly labelled diagrams how you could carry out an experiment to separate a mixture of dyes (or indicators) using thin-layer chromatography.
Answer
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Preparation of the Plate: A thin-layer chromatography (TLC) plate is coated with a thin layer of stationary phase (usually silica gel).
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Application of the Mixture: Apply small drops of the dye mixture onto the base line of the TLC plate, spaced evenly.
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Development: Place the plate in a developing chamber containing a solvent. The solvent will rise up the plate by capillary action.
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Observation: Remove the plate and mark the solvent front. Observe the different colors corresponding to the components of the mixture, noting the distance traveled.
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Labeling: Clearly label the TLC plate with the initial spot positions and the resulting separated components.
Step 4
Describe with the aid of clearly labelled diagrams how you could carry out an experiment to separate a mixture of dyes (or indicators) using column chromatography.
Answer
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Column Setup: Prepare a chromatography column packed with a stationary phase (e.g., silica gel or alumina).
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Application of the Mixture: Apply the dye mixture at the top of the column, typically dissolved in a small volume of solvent.
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Elution: Add the mobile phase solvent gradually to the column, allowing it to run through the packed stationary phase. Different components will travel at different rates based on their affinities for the phases.
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Collection: Collect the separated components in different receivers as they exit the column, allowing the identification of the various colors.
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Labeling: Each collected fraction should be labeled for clarity, indicating the composition and the order of elution.