Lab Report

Lab ReportJune 172013General Chemistry II - 182

Bezawit WubeExperiment 4 Summer session

Abstract:Students will have the opportunity to learn how mixtures of compounds can be separated and determine what food dyes are found in certain foods by using paper chromatography. They will learn how solubility is affected by polarity.Purpose: To learn how mixtures of compounds can be separated To learn what food dyes are found in certain foods In this exercise we will separate food dyes from a variety of sources. The separation is based on polarity. Most dyes are all polar and will be soluble in water

Materials used:

Distilled water1 Salt1 Ruler1 Scissors1 Stapler1 Pencil1 Tape16 Toothpicks1 Kool-Aid drink mix: strawberry1 Kool-Aid drink mix: grape1 Set of food colorings usually boxed in small vials of red, yellow, green, & blue1 Small bag of M&M candyBeaker, 50 mL, plastic1 Petri dish, 60 mm1 Well-Plate-24Experiment Bag Chromatographyof Food Dyes 1 FDC Blue Dye #-1 - 0.5 mL in Vial1 FDC Blue Dye #-2 - 0.5 mL in Vial1 FDC Red Dye #-3 - 0.5 mL in Vial1 FDC Red Dye #-40 - 0.5 mL in Vial1 FDC Yellow Dye #-5 - 0.5 mL in Vial1 FDC Yellow Dye #-6 - 0.5 mL in Vial1 Unknown - 0.5 mL in VialSpecial Papers Bag Special PapersBag-CK-2 3 Filter Paper Chrom 14x7 cm

Procedure:1. Using the 50-mL beaker, dissolve a pinch of salt into 50 mL of warm (room temperature) distilled water. Stir until completely dissolved and set aside.2. . Obtain two sheets of Filter Paper Sheets Chromatography 14 x 7cm from your LabPaq3. . On Sheet 1, from left to right, lightly label in pencil each section between the cross lines with the abbreviation for the six FD&C food colors from your experiment bag that will be tested, i.e., B1, B2, R3, R40, Y5, and Y64. Also on Sheet 1, but now right to left, place the labels KG and KS to represent the Kool-Aid Grape and Kool-AidStrawberry drink mixes to be tested5. On Sheet 2 from left to right, lightly label in pencil each section between the cross lines with the abbreviation for the grocery store food colorings that will be tested, i.e., R, Y, G,B a6. Also on Sheet 2, but now from right to left, place the label UK for unknown and then M plus A letter for the color of four different candies from your bag of M&Ms, i.e., MR, MY, MB, etc.7. Set Sheet 2 aside and perform the following for Sheet 1. After you have completed the experiment for Sheet 1, repeat for Sheet 2.8. For each dye on the sheet to be tested9. Now form the paper into a cylinder with the edges touching, but NOT overlapped, and staple at the top and bottom.10. The salt water (~0.1% NaCl) you previously prepared will be your eluting solvent and a petri dish will be your elution chamber. Pour salt water into the clean and empty petri dish to depth of about 1/2 cm.11. Set your cylinder next to the petri dish with the spots at the bottom and look to make sure the solvent level is below the line of dye spots12. Carefully drop the dye cylinder into the eluting chamber, making sure not to touch the petri dish sides13. When complete remove the cylinder from the chamber and immediately mark the top of each solvent-front with a pencil. Allow the paper to dry for several minutes14. Then measure to the nearest millimeter and record the heights of the dye and solvent-front in each column:15. Calculate and record the Rf value for each spot: Rf = dye distance/solvent distance16. Repeat Steps 8 through 15 for the items listed on Sheet 2.17. 17. By comparing the color columns of the unknown sample and the food items with those of the FD&C food dyes it is possible to determine which dyes are used in the Kool-Aid, in the grocery food colorings, and in the M&Ms.Observations: Data table Sheet1:FD&C Food Colors

SubstanceBlue1Blue2Red3Red40Yellow5Yellow6Splvent

Distance(mm)

Rf

Data Table Sheet1:Drink Mixes

SubstanceKool-Aid GrapeKool-Aid strawberrySolvent

Distance(mm)

Distance(mm)

Rf

Data Table Sheet2:candy colors

SubstanceM&M GreenM&M Yellow M&M BlueM&M RedSolvent

Distance(mm)

Rf

Questions:A. Why cant a pen be used to draw the baseline on the chromatography paper? B. Why it is important to stop the chromatograph before the solvent reaches the top of paper? C. Why is it important to keep the dye spots above the solvent level? D. Why is it important to mark the solvent level on the chromatography paper when you remove it from the petri dish?