Chromatography Questions PDF

# Chromatography Questions 1. Consider the separation of black ink on paper using water * What is the stationary phase? * What is the mobile phase? 2. What term is used to describe the way the solvent moves up the stationary phase? 3. How must the base line be drawn (using what and why)? 4....

# Chromatography Questions 1. Consider the separation of black ink on paper using water * What is the stationary phase? * What is the mobile phase? 2. What term is used to describe the way the solvent moves up the stationary phase? 3. How must the base line be drawn (using what and why)? 4. What can you say about dyes that move a long way the stationary phase in terms of their solubility in the solvent? 5. What can you say about dyes that do not move very far in terms of their affinity for the stationary phase? 6. Where do you draw the solvent front? 7. Different black ink pens made by different companies are likely to contain different dyes. Describe how the chromatograms for two different pens will compare. 8. What is the formula for calculating an Rf value? 9. Would you get the same Rf values if a different solvent was used e.g. ethanol compared to water? 10. Calculate the Rf values for X Y and Z (to 2dp) ## Chromatogram Diagram The diagram shows a chromatogram with three spots, labelled X, Y, and Z. * The solvent front is at 3.20 cm * The origin is at 0.00 cm * The distance travelled by spot X is 2.75 cm * The distance travelled by spot Y is 2.15 cm * The distance travelled by spot Z is 1.70 cm ## Calculating Rf values The following equations can be used to calculate the Rf value for spot X, spot Y, and spot Z. $R_f = \frac{distance travelled by substance}{distance travelled by solvent}$ $R_f_X = \frac{2.75}{3.20}$ = 0.86 (to 2dp) $R_f_Y = \frac{2.15}{3.20}$ = 0.67 (to 2dp) $R_f_Z = \frac{1.70}{3.20}$ = 0.53 (to 2dp)