Question

1. you will be doing chromatography with a mixture of water and n-propanol. would it make sense to add hexane to this mixture to try and make it work better? EXPLAIN 2. Two cars full of people took a trip today. car A had a lot of kids and stopped at lots of rest stops and gas stations to give them a break. Car B had just adults in it, and only stopped once. Of course Car B got to the destination first. Explain how this is an analogy for the chromotography you are doing in this experiment.

Answer 1

Sol :-

(a). Hexane is a common non-polar solvent which is used in both thin-layer and chromatography . It can be used with a variety of polar solvents such as petroleum ether, pentane, carbon tetrachloride, benzene, toluene, chloroform, ethyl ether, ethyl acetate, ethanol, acetone, acetic acid, and methanol. The higher the percentage of a polar solvent, the faster the compounds will elute. The more polar the solvent, the faster compounds will elute, regardless of the polarity of the compound. This means changing the solvent polarity cannot change the order compounds elute from a TLC or column. The polar solvent would move a polar compound farther than a non-polar compound.  

From the above discussion, it is very clear that the addition of the non-polar solvent hexane will lead the clear separation of the non-polar component of the compound. As it will have a greater role in decrease the polarity of the combined three solvents as eluent. Thus it is more efficient if the hexane will be added in the mixture of the solvents of water and methanol since both are the highly polar solvents. To make the clear separation it will more useful to add the hexane in it.

(b). Car A has n-propanol which interacted with hexane at various destinations and reached the destination later

Whereas , Car B has water which are adults . As water haven't interacted with any of the solvent having same affinity, it reached the destination earlier.