2 3 Thin layer Chromatography Post Lab Questions 1 4pts What if any are the consequences of failing to remove a TLC plate from the solvent chamber before the eluent reaches the top of the plate How will this affect your ability to interpret use the plate s data Be detailed in your explanation I believe that the consequence of letting them reach the top of the TLC plate is that the chemicals would start to merge together thus making you unable to see the separation and therefore you wouldn t be able to determine the Rf values 4pts How would the TLC plate development be affected if you only allowed the eluent to move halfway up the plate before removing it and marking the solvent front Be detailed in your explanation The consequence of this could be that the component spots may be overlapping from not letting it fully reach the top If one of the components may have a dot that s much higher up but by stopping it short it will cause it to possibly overlap making it much harder to determine the identity of the component and the compound 4pts Assuming that the separation of a binary mixture in ideal circumstances would be relatively small less than 0 5 cm what would be the result of applying too large of a spot of this mixture to the TLC plate How would it affect your ability to distinguish one component from the other on the plate How would it affect your Rf values Draw a sample TLC plate to help illustrate your answer If the spot is too big it may start to overlap with the other compound spots making it hard to distinguish one compound spot from another Thus it would make it hard to determine the Rf values and even if you were able to distinguish the compound spots from one another the Rf values may not be accurate And if there are two spots that are close together and you place one big dot you may not be able to see the two dots separate 4 4pts What would happen if your origin line was oriented so low on the TLC plate that when it was lowered into the TLC chamber it was positioned below the level of the developing solvent eluent If the origin line was too low then the compounds would just end up dissolving in the solvent instead of travelling up the plates 5 4pts Unknown compound Q is spotted on a TLC plate that is then developed in dichloromethane The solvent front is measured at 5 2 cm and the distance traveled by compound Q is measured at 3 4 cm A sample of aspirin is spotted on a TLC plate that is then developed in dichloromethane The solvent front is measured at 4 15 cm and the distance traveled by aspirin is measured at 2 70 cm What can be determined about the identity of compound Q in light of this data Compound Q Rf 3 4 5 2 0 654 Aspirin Rf 2 7 4 15 0 650 They have Rf values that are incredibly close so it would be a viable conclusion that compound Q is in fact aspirin however more information would be necessary to guarantee that they are 100 the same 6 4pts Is it possible or experimentally useful to compare thin layer chromatography results for an unknown compound and a reference standard developed on separate TLC plates of differing lengths ie 5cm vs 7cm Why or why not Be detailed in your explanation It is very possible and experimentally useful to compare the two even if the TLC plates are of differing lengths because ultimately we will be looking at the Rf values which are ratios thus the length shouldn t cause any kind of major effect
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