Which procedure was more efficient at separating mixture into its compounds A pu

Question

Which procedure was more efficient at separating mixture into its compounds A pure liquid has a com uni boiling point, bur a liquid with a constant Soiling point it not necessarily pure. Explain. What effect does a reduction in the atmospheric pressure have on the boiling point of a liquid? Why doesn't a pure liquid in distilling flask vaporize all a once when the boiling temperature is reached? Why is it dangerous to heat a liquid in a distilling apparatus that is closed tightly at every joint and has no vent to the atmosphere? Why is it important that the cooling water in a distillation apparatus enter the condenser jacket at the lower end and exit at the upper end. and not vice versa? Why should a distilling flask be filled to not more than two-thirds of its capacity at the beginning of a distillation procedure?

Explanation / Answer

4) A pure liquid has fixed boiling point, so everytime it is boiled, it boils at constant boiling point.During distillation the temperature remains constant throughout the process,while the liquid boils to form vapour.(be it pure or not).

5)The boiling point of the liquid is the temperature, when the temperature when the vapour pressure of the liquid becomes equal to the atmospheric pressure.so when atmospheric pressure is reduced boiling point is ,consequently, reduced.

6)At boiling point, the molecules of liquid present in the surface vaporise first as they are held less strongly by the intermolecular forces of attraction than the molecules present in the bulk(volume).Also ,the energy required for phase change is slight more than that needed to bring the molecules to b.pt.Although a molecule reaches the b.pt , it does not necessarily posess extra energy to escape freely like gas molecules .

Those molecules that does not possess the extra energy needed for phase change may return to the liquid phase after cooling.Thus, the molecules move in and out of the liquid ,thereby offering some amount resistance to the escaping molecules.So all molecules doesnt escape at once.

7)The vapour pressure of the constant boiling liquid will increase ,and may apply excess pressure on the apparatus and make it to break.

8)The cooling water when passes through the condenser absorbs the heat of the vapours of the liquid boiling in the flask and form water vapours to some extent .As the vapours move up always so the the upper end of the condenser jacket is left open for water vapours to escape and thereby cool the water.Else the water vapours would not find any vent and mix with the cooling water introduced at the top and heat up the water.

9)Because there needs to be enough space above the boiling liquid in the distillation flask and that the liquid vapours are not pushed into the condenser jacket.

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