The diagram shows a chromatogram after the run is complete. Which label marks the level reached by the solvent, called the solvent front?
Question 1 Report
The diagram shows a chromatogram after the run is complete.
Which label marks the level reached by the solvent, called the solvent front?
Answer Details
Two horizontal lines appear on a finished chromatogram. The lower one is the pencil baseline where the sample was applied; the upper one is the solvent front, the highest level the solvent reached before the paper was taken out and that level was marked. On this diagram the lower line carries the label P and the upper line carries the label Q, so Q marks the solvent front.
The remaining label sits on a circle part-way up the paper, which is a separated spot rather than a level. The front must be pencilled in immediately, before the solvent evaporates and its position is lost, because both distances used in the Rf calculation are measured between these marks.
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