In this worksheet, we will practice describing the purification of solvents and other liquids by distillation, assessing hazards and common errors.
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.
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
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.
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.
Which of the following pieces of apparatus is not typically used in distillations?
- AHot plate
- BKeck clip
Which of the following pieces of apparatus is not used in distillations?
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.
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