CLEAR HANDWRITING Post Lab Questions Use a temperature-composition diagram to ex
ID: 1028334 • Letter: C
Question
CLEAR HANDWRITING
Post Lab Questions Use a temperature-composition diagram to explain why fractional distillation of two components is more easily accomplished if the components have boiling points that differ by 20 °C or more. 1. 2. Why were one or two boiling chips added to the A-Bmixture prior to the start of the fractional distillation? 3. Why is it important to perform a fractional distillation slowly? What happens if a fractional distillation is done very quickly by rapidly raising the temperature of the heat source? If a fractional distillation failed to separate two components efficiently, what alternatives would one consider to effect clean separation by distillation? 4.Explanation / Answer
1. Distillation is the technique used to separate components in liquid, based on the difference in their boiling point. Fractional distillation is generally used for separating mixtures of liquids with difference in their boiling points by more than 20oC.If the difference in boiling point of the two components is less than 20oC, the separation will not be effective as the the two components will distilled out together. In fractional distillation the components with low boiling point will pass through the fractional column while the component with high boling point will condense at the bottom.
2. The boiling chips are added to the A-B mixture during fractional distillation as it hepls in controlled boiling and prevents overheating of the liquid in the flask, and also prevent the bumping of the liquid mixture into the condenser.
3. Degree of separation in fractional distillation depends on the rate at which it is performed. The best results for separation is obtained when the distillation is carried out slowly as it increases the number of evoparation and condensation in the fraction distillation column. When fractional distillation is performed rapidly at high temperature, the components will not separate properly with unwanted component in the final mixture.
4. If fractional distillation failed to separate two components then one could consider the follwing alternatives:
a. Using more efficient fractionating column with more theoritical plates (more condensation-evopation cycles ). This can be achieved by inceasing the surface area in the fractionating column which in turn inceases the contact time of vapor and liquid, resulting in better separation
b. The heat applied should be constant for effective separation.