ANSWER ALL QUESTIONS PLEASE THANK YOU WILL BE HIGHLY RATED 1 of 3 Mid Term Exam
ID: 489091 • Letter: A
Question
ANSWER ALL QUESTIONS PLEASE THANK YOU WILL BE HIGHLY RATED 1 of 3 Mid Term Exam 1. Do all the mixtures of two different organic compound exhibit a broad melting point range? Explain. 2.Do organic compounds that exhibit polymorphism have different melting points? Explain 3. Why is it not good practice to mix two components by simply stiming them together and then sampling them from a mixed melting point? 4. A student accidentally broke some pieces of glass which fell into the sample. The student found that the melting point for that sample was 187-9. Is it necessary for the student to take the melting point again? 5. Can an azeotropic mixture be separated by distillation? Explain. 6. A student forgot to put boiling stones while performing a distillation and started heating the liquid; suddenly, he remembered that he forgot to do so. Should he a) Continue with the distillation. b)Add boiling stones to the hot liquid. 7. Could cyclohexene (bp 80°C) be separated from hexane (bp 690C) via the distillation process? Explain 8.A mixture of two miscible liquids with widely different boiling points is distilled. The temperature of the distilling liquid is observed to plateau, then drop before rising again. Explain the drop in the temperature. 9. Would water be an appropriate recrystallization solvent for each of the following compounds? Explain a) (mp 80 b) (mp 94)Explanation / Answer
1. No , because eutectic mixture means (a mixture of substances having minimum melting point) , melt with a sharp melting point range
2.Yes , because variations in the intermolecular attraction of different crystalline forms can cause polymorphs to have different but sharp melting point
3. It is not good practice because stirring two solid components does not yeild a homogeneous mixture. A small sample for a melting point determination might this be practically 100% one component .
4. No, insoluble impurities such as glass does not affect melting point.
5. No, because an azeotrope is a mixture of constant composition with a constant boiling point just as that of the pure component.
6. Cool the liquid and add boiling stone because it is safe and not affected the distillation .
7. No, because distillation can performed where the boiling point difference between both compound atleast 20 0C
8.The temperature drop because the lower boiling compounds finishes distilling before the vapours of higher boiling compound can fill the distillation head.
10. A. Yes because they are miscible with each other
10.B. NO because they are immiscible with each other
11.A. if the melting point is lower than the boiling point of solvent used. A very impure compound may oil out because the impurities depressed the melting point below room temperature.
11.B. Reheat the mixture and the allow it cool slowly.
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