Question

Experiment Lab Questions: Distillation of Alcohol

Reagents:

(1) Ethanol (C₂H₅OH) [ MW = 46.07 g/mol density = 0.789g/mL boiling point = 78.37 C ]

(2) Red food dye (non-volatile)

Questions:

1. What is the theoretical Yield

2. How can we improve the efficiency of this distilation experiment?

3. What is the reason for a sharp increase in temperature at one point?

4. What is the reason we can assume that distillation is completed when the temperature drops?

5. a. Discuss sources of error b. predict how boiling points may change as surrounding pressure changes c. explain and give examples of vacuum distillation

Lab Procedure: https://imgur.com/a/9MMTS0p

Answer 1

1. Theoretical yield will be Red food dye as it is non volatile so it will not be distillated .

2.We can improve the distillation efficiency in lab by slowly heating the distillation apparatus as distillate the ethanol in a very slow rate taking maximum time as possible and also maintaining the column temperature at around 75 c

3. when the ethanol will start boiling there will be air entrapment within the ethanol which will try to create max. amount of pressure to move upward this will result in foaming as well as sharp temperature increase .This is why one should heat the ethanol  until all of the liquid reach its equilibrium.

4.If a temperature transmitter is installed in the distillation column the temperature which shows in the transmitter is the the temperature of vapour produced so,clearly it can be said that no vapour is coming so the temperature is decreasing hence distillation has been ended.

5.a.the sources of error can be the reading of thermometer if digital thermometer not installed,if the distillation is carried vary fast foaming may occur, if the cooling medium provided is above 5-10 c vapour may go outside the collection flask which will lead to calculation error

b.boiling point increases as pressure increases and decreases if pressure decreases.

c. vacuum distillation is the way of distillating high bp components in very low temperature by decreasing  their pressure less than atmospheric pressure. e.g:The bp of lube base oil is 450 c in 1 atm but one can distillate it in 250 c by keeping the pressure of distillation column 0.001 atm