I keep going back and forth on the answer?? A student analyzes the product of hi
ID: 894928 • Letter: I
Question
I keep going back and forth on the answer??
A student analyzes the product of his fractional distillation and is dismayed by his results. The GC showed a nearly equal concentration of the two components he was trying to separate (the GC should show a more pure product than what he started with). Choose the statement that best describes the human error responsible for these results. Can you please explain why you think your selected answer is correct over the others.
1. The student did not inject his sample on the GC correctly.
2.The student did not properly clean his glassware.
3. The student was eager to finish and cranked the heat.
4. The student did not heat the sample enough.
1. The student did not inject his sample on the GC correctly.
2.The student did not properly clean his glassware.
3. The student was eager to finish and cranked the heat.
4. The student did not heat the sample enough.
Explanation / Answer
If the ratio of the more volatile to the less volatile components of the mxture injected in GC is seen equal even though they are not, the reason could be,
4. The student did not heat the sample enough.
It cannot be due to wrong injection of sample on the GC, becuase than ratio must not change. Cleaning the glassware is removed from option becuase it is not part of the procedure for injection on GC here. Even when you heat the sample fast, it will effect the separation of the components but not the ratio. A faster heating means less time spent on stationary phase so less separation. So it has to be due to 4. not heating the sample at enough temperature to vaporize all of the sample injected. If say 50 % sample is volatilized in GC, the ratio of higher volatile fraction would be more to the low volatile component. since, it is the less volatile component which needs greater temperature for converting it into gaseous phase before it goes onto the column for separation.