Worksheet: Distillation

In this worksheet, we will practice describing the purification of solvents and other liquids by distillation, assessing hazards and common errors.

Q1:

What is the main reason for adding a stir bar to the pot still in a distillation?

  • AStirring the liquid reduces the risk of bumping.
  • BStirring the liquid prevents phase separation as the temperature increases.
  • CStirring the liquid ensures the vapor composition is uniform.
  • DStirring the liquid increases the rate of boiling, making the distillation more efficient.
  • EStirring the liquid allows it to be heated more uniformly.

Q2:

How could elastic bands be used in a vacuum distillation?

  • ATo improve the vacuum seal by applying tension to the condenser joints
  • BTo improve the condensation rate by insulating the condenser joints
  • CTo secure the thermometer in the correct position near the opening of the condenser
  • DTo prevent breakage by securing the apparatus in an upright position
  • ETo prevent water leakage by securing the condenser tubes in the correct positions

Q3:

When performing a vacuum distillation, why is it often advantageous to use a pig adapter?

  • AMultiple fractions can be collected without releasing the vacuum.
  • BThe distillate can be protected from contamination if bumping takes place.
  • CSamples of the distillate can be collected without releasing the vacuum.
  • DMultiple fractions can be collected and stored at different vacuum pressures.
  • EA larger volume of distillate can be collected.

Q4:

Which of the following precautions is most important for ensuring that the apparatus for a vacuum distillation is well sealed?

  • AThe ground glass joints are secured with Keck clips.
  • BThe condenser is maintained at a low temperature.
  • CThe receiving flask is supported by a jack.
  • DThe ground glass joints are greased.
  • EElastic bands are stretched between the still head and condenser.

Q5:

Which of the following pieces of apparatus is not typically used in distillations?

  • AHot plate
  • BKeck clip
  • CFunnel
  • DCondenser
  • EThermometer

Q6:

Which of the following pieces of apparatus is not used in distillations?

  • A
  • B
  • C
  • D
  • E

Q7:

A student sets up a vacuum distillation using the glassware shown, in addition to other apparatus. Some connectors and other parts of the glassware are labeled.

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To which position should the vacuum pump be connected?

Which positions should be supported by a clamp?

  • A6 and 10
  • B4 and 6
  • C4 and 5
  • D3 and 10
  • E3 and 5

To which position should the pig adapter be attached?

To which female connectors would the attachment of Keck clips be potentially hazardous?

  • A4 and 5
  • B6 only
  • C5 only
  • D4 and 9
  • E6 and 9

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