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Why doesn't all of the liquid in a distillation flask vaporize at once when the boiling point isreached?
Not all the molecules will reach the boiling point all at once. Some will vaporize quicker than others.
Why should a distillation flask not be filled much more than half-full?
Bumping (liquid boiling into condenser) occurs. The condenser and distillate will be contaminated with the undistilled liquid.
What is the disadvantage of using a distillation flask whose capacity is four or five times (or more) the volume of the liquid being distilled?
1) lower the yield of distillation.2) rate of distillation reduced, more time consuming.
If the thermometer bulb is not kept moist with condensate during a distillation, will the boiling point reading tend to be high or low? Explain reasoning.
Low, because vapor is condensing below the position you're measuring.
If a liquid is contaminated with a soluble, but nonvolatile, solid, would you expect the impure liquid to have a higher or lower boiling point than the pure liquid?
no effect because nonvolatile solids do not contribute to the vapor pressure of the liquid
Use a temperature - composition diagram to explain why fractional distillation of twocomponents is more easily accomplished if the components have boiling points that differby 20 oC or more.
If the difference is less than 20 degrees celsius the separation of the two components will not be effective because the two components will not distill out together
Why was a stir bar added to the cyclohexane - toluene mixture prior to the start of the fractional distillation?
1. It helps in a controlled boiling
2. It prevents overheating of the liquid present in the flask and mixture into condenser.
Why is it important to perform a fractional distillation slowly? What happens if a fractionaldistillation is done very quickly by rapidly raising the temperature of the heat source?
A slow, even distillation is necessary to achieve a good separation because only under these conditions will vapor and liquid be in equilibrium with one another in the distillation apparatus. If a mixture is heated too rapidly the rising vapor will have a chance of being carried over to the receiver without condensing.
If a fractional distillation failed to separate two components efficiently, what alternatives would one consider to effect clean separation by distillation?
the addition of a fractional column through a fractional still
