Thin layer chromatography of a mixture shows the following observation: The correct order of elution in the silica gel…

Step 1: Understand TLC and Column Chromatography Relationship

TLC and column chromatography (both using silica gel) share the same principle: differential adsorption. The TLC $R_f$ value directly predicts the elution order in column chromatography:

• Higher $R_f$ in TLC = elutes first in column chromatography (less polar, weaker adsorption)
• Lower $R_f$ in TLC = elutes last in column chromatography (more polar, stronger adsorption)

Step 2: Read $R_f$ Values from TLC

From the TLC figure (silica gel, same adsorbent as column):

• Compound C: travels furthest from baseline → highest $R_f$ → least polar
• Compound A: travels intermediate distance → intermediate $R_f$ → intermediate polarity
• Compound B: travels shortest distance → lowest $R_f$ → most polar

Step 3: Determine Elution Order

In silica gel column chromatography:

• Least polar (weakest adsorption) → elutes first
• Most polar (strongest adsorption) → elutes last

Order of elution:

1. A (highest $R_f$, least polar → exits column first)
2. C (intermediate $R_f$ → exits second)
3. B (lowest $R_f$, most polar → exits last)

Step 4: Conclusion

Correct order of elution: A, C, B → Option (a)

Key Points to Remember:

• TLC $R_f$ and column elution order are directly correlated (same adsorbent/solvent system)
• High $R_f$ in TLC = elutes first in column = less polar
• Low $R_f$ in TLC = elutes last in column = more polar
• TLC is widely used to predict and monitor column chromatography separation