1. Define simple and fractional distillations. 2. Describe the similarities and
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Question
1. Define simple and fractional distillations. 2. Describe the similarities and the differences between simple and fractional distillations 4. In your own words describe the theory of distillation as described on pages 87 to 91·(ou may not quote the book, you must read the chapter pages. understand the section and put the meaning of the passage into your own words) 5. What is an azeotrope and give a real word example? 6. What are the advantage(s) of simple distillation over fractional distillation? When would a chemist use simple distillation rather than fractional distillation? 7. What are the advantage(s) of fractional distillation over simple distillation? When would a chemist use fractional distillation rather than simple distillation? 8. Why does a packed column in fractional distillation better able to separate compounds with similar boiling points than simple distillation? 9. Given what you have leamed about simple and fractional distillation describe which technique would be better to separate toluene and cyclohexane?Explanation / Answer
1.Simple distillation is a procedure by which two liquids with different boiling points can be separated. With the help of simple distillation a pure liquid can be obtained by condensing the vapour of the liquid mixture.
Fractional distillation is the process of heating a chemical mixture to separate out the various components in that mixture.
2.Differences:-
a. Simple distillation is the method used to separate substances in mixtures with significantly different boiling points, while fractional distillation is used for mixtures containing chemicals with boiling points close to each other.
b. Simple distillation will only have one distillation (vaporization-condensation) cycle in the whole process, while the fractional cycle will have at least two cycles.
c. Fractional distillation will use additional equipment called the ‘fractionating column’, while the simple distillation dosnt need that column.
d. Simple distillation is often used to separate the liquid substance from the solid substance,where as in fractional distillation mainly liquid mixtures are used.
Similarities:-
a.They both uses the same equipment and they both separate mixtures.
3. A chemist actually carry out many condensations and distillation inorder to get a pure compound.
4.87-91 page number is not available in question.
5.Azeotrope-Azeotropes are defined as the mixtures of liquids which boil at constant temperature like a pure liquid and possess same composition of components in liquid as well as in vapour phase.
ex-As we know the boiling point of azeotropes are either higher or lower than the boiling points of thieir constituents.So taking an example of ethanol(bp 78.4oC) and water (bp 100oC) , while the azeotrope boils at 78.2oC.
6.Advantage of Simple distillation-
a.It is not that expensive as compared to fractional distillation(the column costs much).
b.Compared to fractional distillation techniques it does not require more energy.
c.In one cycle it gives the desired/quality product.
Disadvantages:-
a.Since the mixture in simple distillation is only boiled and recondensed once, the final composition of the product will match the composition of the vapor, which means it may contain significant impurities.
b.Heating a mixture to boiling point could cause undesirable chemical reactions to occur, which may be a problem if we are trying to isolate a specific product.
7.Advantages of Fractional distillaton:-
a.It has high efficiency. Fractional distillation systems have up to 50 plates at atmospheric pressure. For higher efficiency, distillation columns can be stacked for maximum efficiency.
b.Fractional distillation is easy to use. we only required to operate the maintaining conditions.
c.It is easy to use.
Disadvantages:-
1.fractional distillation is expensive because it requires large structures, heavy-duty materials, and specialized machineries.
2.It itself is not harmful but the for an example lile refining crude oil leads to release in harmful chemicals.
3.It might get exlode.
8. A packed column is better because Inside the column, the downflowing reflux liquid provides cooling and condensation of upflowing vapors thereby increasing the efficacy of the distillation tower. The more reflux and/or more trays provided, the better is the tower's separation of lower boiling materials from higher boiling materials.
9.Simple Distillation would be better to separate toule and cyclohexane.
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