To Separate Mixture Components by Chromatography (Class 10 Chemistry Practical)
To separate and identify the different pigments in plant leaves or ink using paper chromatography.
TL;DR: To separate and identify the different pigments in plant leaves or ink using paper chromatography.
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Aim: To separate and identify the different pigments in plant leaves or ink using paper chromatography.
Materials Required
- Chromatography paper
- Beaker
- Solvent (alcohol or petroleum ether)
- Green leaf or colored ink
- Pencil
- Clips
- Scissors
Theory
Paper chromatography is a separation technique based on differential solubility and adsorption. Different pigments move at different rates (Rf values) in the solvent. Pigments in plants include chlorophyll a, chlorophyll b, carotene, and xanthophyll, each with distinct colors and Rf values.
Procedure
- Cut a strip of chromatography paper and draw a pencil line 2 cm from the bottom
- Crush a green leaf in a little solvent to extract pigments
- Apply the extract as a small spot on the pencil line using a dropper
- Pour the solvent into a beaker to a depth of 1 cm
- Hang the paper strip in the beaker using a clip such that the spot is above the solvent level
- Allow the solvent to move up the paper (capillary action) until it reaches near the top
- Remove the paper and immediately mark the solvent front line with pencil
- Observe the different colored bands of pigments on the paper
- Calculate Rf values for each pigment: Rf = Distance traveled by pigment / Distance traveled by solvent
Observation
Different pigments separate and appear as distinct colored bands: Yellow (carotene), orange (xanthophyll), blue-green (chlorophyll a), and yellow-green (chlorophyll b). Each pigment has a characteristic Rf value.
Result
The leaf pigments are successfully separated by paper chromatography, revealing four main pigments. The Rf values and colors confirm the presence of chlorophyll a, chlorophyll b, carotene, and xanthophyll.
Precautions
- Use a pencil (not pen) as the baseline as pen marks may dissolve in the solvent
- Keep the spot above the solvent level initially to prevent direct dissolution
- Avoid touching the paper with fingers to prevent contamination
- Ensure the chamber is sealed to maintain constant solvent vapor
- Work in a well-ventilated area due to solvent fumes
Viva Questions
What is paper chromatography?
Paper chromatography is a separation technique that separates components based on their differential movement in a solvent.
What is the Rf value?
Rf (retention factor) is the ratio of distance traveled by solute to distance traveled by solvent front.
Which pigment travels farthest in chromatography?
Carotene (orange) travels farthest as it is most soluble in the solvent used.
Why are there multiple pigments in a leaf?
Leaves contain multiple pigments for efficient photosynthesis and light absorption at different wavelengths.
More Class 10 Chemistry Practicals
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- To Study a Double Displacement (Precipitation) Reaction
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- To Verify the Law of Conservation of Mass
- To Study the Effect of Temperature on Reaction Rate
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