If you eluted a TLC of a compound using 60% hexanes / 40% ethyl acetate as the solvent and obtained an Rf value of 0.5. If you changed the solvent system to 30% hexanes / 70% ethyl acetate, how would the Rf value change

The Rf value change will be  >  0.5

Explanation:

Given that Change in Solvent is proportional to change in polarity of solvent system

The change from solvent composition of 60/40  to 30/70 will cause an increase in the polarity of the system .

and Increase in Polarity = Increase in Rf value  because the compound will move to a higher distance

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