Worksheet: Rotary Evaporation

In this worksheet, we will practice describing the removal of solvent in vacuo by rotary evaporation, assessing hazards and common errors.

Q1:

Which component of a rotary evaporator is typically secured with a Keck clip?

  • AEvaporating flask
  • BCollecting flask
  • CSplash guard
  • DWater bath
  • ECondenser

Q2:

Which component of a rotary evaporator is typically secured with a pinch clamp?

  • ASplash guard
  • BEvaporating flask
  • CCondenser
  • DWater bath
  • ECollecting flask

Q3:

Which piece of apparatus is not used in the normal operation of a rotary evaporator?

  • ATwo-necked flask
  • BVacuum pump
  • CCondenser
  • DWater bath
  • EKeck clip

Q4:

When removing a solvent in a rotary evaporator, which of the following steps is not required?

  • AThe pressure in the flask is accurately measured.
  • BThe solution is placed in a round-bottom flask.
  • CThe condenser is filled with dry ice and acetone or a water flow.
  • DThe collected solvent is disposed of safely.
  • EA Keck clip is used to secure the flask in place.

Q5:

When performing a rotary evaporation, which of the following is not a reason for lowering the pressure gradually?

  • AVigorous boiling may force solution out of the flask.
  • BThe rate of evaporation is more easily controlled.
  • CThe solvent may freeze.
  • DThe condenser may be less effective at very low pressures.
  • EThe contents of the flask may foam.

Q6:

When performing a rotary evaporation, which of the following is not a reason for setting a low water bath temperature?

  • AVigorous boiling may force solution out of the flask if the temperature is too high.
  • BHeating may cause solutes to precipitate.
  • CHeating may cause undesirable reactions of the flask contents.
  • DThe solvent vapor may not condense if the flask temperature is too high.
  • EThe rate of evaporation is more easily controlled.

Q7:

When performing a rotary evaporation, which of the following is the best immediate course of action if the solvent starts to bump?

  • ATurning off the pump
  • BRaising the flask from the water bath
  • COpening the tap to introduce air into the system
  • DStopping the rotation
  • EIncreasing the set pressure

Q8:

When a rotary evaporation is complete, in which order should the following actions be performed?

  1. Introducing air into the system
  2. Turning off the pump
  3. Stopping the flask rotation
  • A3, 1, 2
  • B3, 2, 1
  • C1, 3, 2
  • D1, 2, 3
  • E2, 3, 1

Q9:

When setting up a rotary evaporation, in which order should the following actions be performed?

  1. Lowering the flask into the water bath
  2. Gently applying the vacuum
  3. Starting the flask rotation
  • A3, 1, 2
  • B1, 2, 3
  • C2, 1, 3
  • D3, 2, 1
  • E2, 3, 1

Q10:

The water bath of a rotary evaporator is set to 50C. Which of the following solvents could be removed safely and efficiently at this temperature?

  • ADichloromethane
  • BWater
  • CAcetone
  • DChloroform
  • EDiethyl ether

Q11:

A student is about to remove a volatile solvent from his reaction mixture using a rotary evaporator. After the water bath has been filled and water begins to flow through the coil condenser, but before the pump has been turned on, the apparatus is assembled as shown below.

Which of the following is not a mistake in the setup of this apparatus?

  • AThe evaporator flask is already immersed in a hot water bath.
  • BThe vent tap has not been closed before turning on the pump.
  • CThe evaporator flask is rotating too rapidly.
  • DThe solvent collection flask has not been secured with a pinch clamp.
  • EThe solvent collection flask has not been emptied.

The reaction mixture contains a surfactant and is likely to foam under vacuum. How could the rotary evaporator setup be modified to to account for this possibility?

  • AImmerse the evaporator flask in ice during the evaporation.
  • BAttach an anti-climb guard to the evaporator flask.
  • CIncrease the water bath temperature.
  • DAdd bumping granules to the evaporator flask.
  • EIncrease the water flow rate in the condenser.

During rotary evaporation, the reaction mixture begins to foam. How should the student respond?

  • AStop the rotation of the evaporator flask.
  • BOpen the vent tap.
  • CRaise the evaporator flask out of the water bath.
  • DIncrease the set pressure on the pressure controller.
  • ETurn off the pump.

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