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?

  • ASeparating funnel
  • BFunnel
  • CStopper
  • DPasteur pipette
  • ERetort stand

Q2:

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

  • AThe separating funnel is inverted and shaken repeatedly.
  • BThe stopper is removed from the separating funnel.
  • CWater or brine are added to the separating funnel.
  • DThe aqueous solution is returned 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?

  • ACentrifuge the mixture.
  • BAdd salt.
  • CStir the mixture.
  • DRemove the stopper from the funnel.
  • 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, 2, 3
  • D1, 3, 2
  • E2, 3, 1

Q5:

A student is extracting a solute into a non-halogenated 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?

  • AClamp the Erlenmeyer flask.
  • BInvert and shake the flask again.
  • CAdd a stir bar to the Erlenmeyer flask and place it on a hotplate.
  • DRemove the stopper from the funnel.
  • EAdd an indicator to the funnel to highlight the liquid-liquid interface.

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

  • ADispense the top layer into another flask, return the bottom layer to the funnel, add pure organic solvent and repeat the extraction.
  • BLeave the top layer in the funnel, add distilled water and repeat the extraction.
  • CLeave the top layer in 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.
  • EReturn the bottom layer to the funnel, add pure organic solvent and repeat the extraction.

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