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Lesson: Liquid–Liquid Separation

Worksheet • 5 Questions

Q1:

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?

  • ARemove the stopper from the funnel.
  • BAdd an indicator to the funnel to highlight the liquid-liquid interface.
  • CInvert and shake the flask again.
  • DAdd a stir bar to the Erlenmeyer flask and place it on a hotplate.
  • EClamp the Erlenmeyer flask.

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.
  • BReturn the bottom layer to the funnel, add pure organic solvent and repeat the extraction.
  • CDispense the top layer into another flask, return the bottom layer to the funnel, add distilled water and repeat the extraction.
  • DLeave the top layer in the funnel, add distilled water and repeat the extraction.
  • ELeave the top layer in the funnel, add pure organic solvent and repeat the extraction.

Q2:

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.
  • A1, 3, 2
  • B2, 3, 1
  • C3, 1, 2
  • D1, 2, 3
  • E3, 2, 1

Q3:

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

  • APasteur pipette
  • BRetort stand
  • CFunnel
  • DStopper
  • ESeparating funnel

Q4:

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

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

Q5:

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?

  • ARemove the stopper from the funnel.
  • BWait.
  • CAdd salt.
  • DStir the mixture.
  • ECentrifuge the mixture.
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