Worksheet: Liquid–Liquid Separation

In this worksheet, we will practice describing the use of separatory funnels for washing and extraction methods, assessing hazards and common errors.

Q1:

Which of the following pieces of apparatus is not typically used when separating liquids?

  • AFunnel
  • BSeparating funnel
  • CStopper
  • DRetort stand
  • EPasteur pipette

Q2:

When extracting a solute from an organic solvent into water, which of the following steps is not required?

  • AThe stopper is removed from the separating funnel.
  • BThe separating funnel is inverted and shaken repeatedly.
  • CThe aqueous solution is returned to the separating funnel.
  • DWater or brine are added to the separating funnel.
  • EThe mixed liquids are left to stand until separation takes place.

Q3:

After washing a reaction mixture, an emulsion is observed instead of separate aqueous and organic layers. Which of the following actions would not improve the separation?

  • AStir the mixture.
  • BRemove the stopper from the funnel.
  • CAdd salt.
  • DCentrifuge the mixture.
  • EWait.

Q4:

After adding a liquid mixture to a separating funnel and inserting a stopper, in which order should the following actions be performed?

  1. Shake or swirl the funnel.
  2. Vent the funnel.
  3. Invert the funnel.
  • A3, 2, 1
  • B3, 1, 2
  • C1, 3, 2
  • D2, 3, 1
  • E1, 2, 3

Q5:

A student is extracting a solute into a nonhalogenated organic solvent using a separating funnel. After inverting and shaking the flask, the apparatus appears as shown.

What must the student do before dispensing liquid from the separating funnel?

  • AAdd a stir bar to the Erlenmeyer flask and place it on a hotplate
  • BAdd an indicator to the funnel to highlight the liquid–liquid interface
  • CClamp the Erlenmeyer flask
  • DRemove the stopper from the funnel
  • EInvert and shake the flask again

A large amount of solute remains in the aqueous layer. After dispensing the bottom layer from the funnel, what must the student do?

  • ALeave the top layer in the funnel, add pure organic solvent, and repeat the extraction
  • BLeave the top layer in the funnel, add distilled water, and repeat the extraction
  • CReturn the bottom layer to the funnel, add pure organic solvent, and repeat the extraction
  • DDispense the top layer into another flask, return the bottom layer to the funnel, add distilled water, and repeat the extraction
  • EDispense the top layer into another flask, return the bottom layer to the funnel, add pure organic solvent, and repeat the extraction

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