1. (1.5 pts) Two substances moved with the solvent front (R=1) during TLC analysis on a normal-phase chromatography, using isopropanol (acetone) as the developing solvent. Can you conclude if they are identical? If yes, why? If not, why? What additional experiment(s) would you perform? 2. (1.5 pts) Briefly compare any three advantages and limitations of column chromatography with those of thin-layer chromatography 3. (1.5 pts) Chemist started to carry out column chromatography on a Friday afternoon, reached the point at which the two compounds being separated were about three-fourths of the way down the column, and then returned on Monday to find that the compounds came off the column as a mixture. Speculate the reason for this. The column had not run dry over the weekend. 4. (1.5 pts) It is common to mix polar solvents (e.g., acetone) with non-polar solvents (e.g., hexane) to obtain an eluting solvent of intermediate polarity. Would it be appropriate to use a water-petroleum ether mixture? Explain your choice and discuss any two advantages or disadvantages. What is petroleum ether? 5. (1.5 pts) The Rf value of compound A is 0.29 when developed in heptane and 0.47 when developed in chloroform. Compound B has an R value of 0.45 in heptane and 0.69 in chloroform. Which solvent would be better for separating a mixture of compounds A and B. Briefly explain your choice. 6. (1.5 pts) Why is it necessary to run TLC in a closed container and to have the interior vapor saturated with the solvent? 7. (1 pt) Rank in order of increasing eluting power for normal phase column chromatography (1 = lowest eluting power; 5 = greatest eluting power). 1:2 ethanol/CHCI 1:1 ethanol/CHCI hexane ethanol CHCI