Topics: Distillation, Temperature, Chemical engineering Pages: 2 (589 words) Published: December 19, 2012
What is the effect of a non-volatile impurity on the boiling point of a substance? of a volatile impurity? A non volatile impurity which is added to the volatile liquid, it's boiling point will increase. It is due to some of effective surface area which is available for evoperation is occupied by non volatile substance. If another volatile impurity is added then 1) if it does not chemically react with given liquid then boiling point will decreade due to increase in vapour pressure. 2) if it chemically react or combine then it will deviate from ideal behaviour and it may increase or may decrease the boiling point of solution in coparision with boiling point of pure solvent. The presence of a non-volatile solute in a solution increases its boiling point. The amount of the elevation of the boiling point depends only on the number of molecules of solute present, and not on their identity. Why is the thermometer bulb positioned near the sidearm of the distillation flask instead of being dipped in the solution? Had you did it in the solution, the thermometer would have measured the temperature of the direct heat from the flame. However, what we want is the temperature at which a substance boils. Hence, by positioning the thermometer near the sidearm of the distillation flask measures the temperature of the vapour which is also the boiling point of that substance. what are the limitations of simple distillation?how to overcome these difficulties you can't purify completely a component only using distillation. If you try to seperate 2 components who have very close temperatures of ebulition, then you won't be able to get a lot more than a 50%-55% concentration with a simple distillation. To get better concentrations, use fractional distillation.

If this still isn't enough, then you'll have to use other methods (chemical reaction to change the properties of your component, then distillation, then another chemical reaction to get your original component back. - or...
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