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JEE Main levelSingle correct optionDifficulty 2 of 3si082

On a silica gel TLC plate, spots A and B are at $2.4 cm$ and $4.5 cm$ from the baseline and the solvent front is at $6.0 cm$ . The $R_{f}$ values of A and B and the compound more strongly adsorbed on silica are

A0.40, 0.75 and B
B0.40, 0.75 and A
C0.75, 0.40 and A
D2.50, 1.33 and B

Answer: B

R_{f} (A) = 2.4/6.0 = 0.40

and

R_{f} (B) = 4.5/6.0 = 0.75

. The compound that travels less (lower

R_{f}

) is held more strongly by the stationary phase, so A is more strongly adsorbed.

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