Assignment:
Experimental Procedure
1. Obtain the following items:
a. 600 ml Beaker
b. A no. 2 lead pencil with a sharp point
c. A ruler graduated in centimeters
d. 2 sheets of 20lb. white copy paper
e. Food dyes (food coloring)
i. Red
ii. Blue
iii. Yellow
iv. Green
f. Eluting solvents of varying polarity
i. Isopropyl alcohol (rubbing alcohol)-low polarity
ii. Tap water/Isopropyl Alcohol (50/50 mixture)-medium polarity
• Plastic wrap
• Stapler
• Round tooth pick with a fine point
2. Cut the copy paper 24 cm long x 12 cm high. Draw a straight line (across the long dimension) 1 cm above the edge of the paper using a number 2 lead pencil.
3. Place equally spaced dots onto the sample line with the number 2 pencil. Label the spots as R for red, B for blue, Y for yellow, G for green, O for orange, P for purple, and K for black.
4. To make the orange dye, mix equal drops of red and yellow dyes. To make the purple dye, mix equal drops of red and blue dyes, and to make the black dye mix equal drops of all the dyes.
5. Put drops of each dye on a flat surface.
6. Begin 1cm from the left hand edge of the paper and using a fine point, place small amounts of each dye on the spots on each of the two chromatography sheets.
7. Let the sample spots dry. Fold the sheets into cylinders making sure the edges don't overlap, and staple the edges together - top, middle, and bottom.
8. Place a minimum amount of the eluting solvent into the 600ml beaker. Be sure the depth is below the sample spot line.
9. Set the paper cylinder into the beaker with the sample spot line above the liquid level.
10. Cover the container to retain solvent vapor inside the chromatography container (beaker).
11. Let the solvent advance up the chromatography paper until it is within a 0.50 inch of the top of the paper, or as high as it will go.
12. The isopropyl / water solvent will advance to roughly half of the height.
13. Remove the cylinder from the container, open it up, lay the sheet flat on pieces of absorbent paper towels and draw a line (#2 pencil) across the solvent front.
14. Measure the distance from the sample spot line to the mid-point of each color spot.
15. *Compute the Rf values for the components of each spot and record them in the space below.
16. Repeat steps 2-13 using a 50/50 mixture of water and isopropyl alcohol as the solvent.
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Solvent
Substance
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Isopropyl
Alcohol
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Water/Isopropyl
Mixture
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Yellow Dye
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Rf = spot distance
Solvent front distance
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Blue Dye
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Red Dye
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Orange Dye
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Purple Dye
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Black Dye
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Based on the Rf values of the different dyes and mixtures in the less polar (isopropyl) and the more polar (mixture), answer the following questions about dyes.
1. Which dye is the most polar?
2. What two components are found in the green dye?
3. Which dye is the second most polar dye?
4. Which dye has large Rf values in both solvents?
a. Is this dye polar? Yes or No?
b. Is this dye non polar? Yes or No?
c. Is this dye attracted to the stationary phase? Yes or No. Explain