Question

What effect would changing the developing solvent from 4:6 hexanes:ethyl acetate to 8:2 hexanes:ethyl acetate have on the observed Rf value of 0.42 from a TLC plate? Explain your reasoning.

Answer 1

Rf value will decrease from 0.42 to 0.21

in your mobile phase

Hexane is non polar solvent and

ethyl acetate is polar solvent

in the first mixture

4 mL if hexane and 6 mL of ethyl acetate

means polar solvent quantity is more than non polar solvent

in second case

8 mL of hexane means compare to above case non polar solvent increased double

2 mL of ethyl acetate means polar solvent decreased half

so overall polarity decreased half

we know that if mobile phase polarity decreases Rf value will decrease