Student C measures distances to a dye spot and to the solvent front from the lowerd edge of a chromatogram ins

Question

Student C measures distances to a dye spot and to the solvent front from the lowerd edge of a chromatogram instead of from the origin line as instructed. he obtains the following values for the measurements:
Dye spot - 12.8 cm
Solvent front - 19.8 cm
his origin line was drawn 2.5 cm from the lower edge. which of teh dyes could have caused the spot? (carmine yellow, visual purple, or skyy blue?)

if student c had followed the instructions for the preparation of the chromatograph, what would be the distance from teh bottom edge of teh chromatogram to the solvent front and to the dye spot in a properly prepared chromatograph developed for teh same period of time?

Answer 1

Your first question does not give Rf values for the dyes to compare. The values both need to have 2.5 subtracted from them to get the correct Rf value (10.3/17.3=0.60. The value using the numbers obtained by the student give 0.64 which is close to the correct value but is still improperly measured. Until the solvent reaches the origin nothing has happened so it is irrelevant where the spot is placed on the plate (so long as it is above the solvent pool).