MediumChemistryHigh School (11–12)Organic Chemistry: Some Basic Principles and Techniques › Purification and Analysis of Organic CompoundsNumericalA-LevelIBNEET
On a TLC plate the solvent front rose 7.5 cm above the starting line…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
On a TLC plate the solvent front rose above the starting line. A mixture gave two spots, at and at above the line. A known compound X, run on the same plate, had an of . Find the of each spot, and say which spot is X.
Need a reminder? The key ideaShow
Purification: sublimation (a solid that turns to vapour and back), crystallisation (hot saturated solution, then cooling), distillation (simple, fractional, under reduced pressure, steam) and differential extraction. Chromatography separates by different clinging to a stationary phase, and , the distance moved by the substance over the distance moved by the solvent front. In steam distillation, .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The lower spot. .
Step 2. The upper spot. .
Step 3. Compare. The upper spot has the same as X, under the same conditions.
Answer: the spots have values and , and the upper spot is compound X.
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