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Lesson: Filtration

Worksheet • 9 Questions

Q1:

After a Büchner filtration, solid is observed in the collected filtrate. Which of the following is the least likely explanation?

  • ASolvent added to wash the filtered solid caused further precipitation in the filtrate.
  • BThe solid passed through the filter paper.
  • CThe filter paper was not properly sealed to the Büchner funnel.
  • DThe Büchner funnel or flask were not properly washed before use.
  • EPrecipitation was caused by cooling of the filtrate under vacuum.

Q2:

What is the main disadvantage of using a smaller funnel for a gravity or a vacuum filtration?

  • ASolvent flows through the funnel more slowly, increasing the time needed to complete the filtration.
  • BThe solid product forms a thicker and more compact layer, making it more difficult to retrieve.
  • CThe funnel is more difficult to handle, increasing the chance of breakages when the apparatus is assembled.
  • DFor a given volume of washing solvent, the final purity of the product is reduced.
  • EThe funnel is more difficult to clean after the filtration is complete.

Q3:

In gravity filtration, filter paper is often folded into a fluted shape, as shown. Why is the efficiency of filtration increased if fluted filter paper is used instead of a simple paper cone?

  • A For a given funnel, fluted filter paper has a larger surface area than a filter paper cone.
  • B The folds in fluted filter paper channel solvent onto the solid contents, reducing the volume of solvent needed.
  • C For a given funnel, fluted filter paper can accommodate a larger solvent volume than a filter paper cone.
  • D When the filtration is complete, it is easier to retrieve a solid product from fluted filter paper.
  • E Fluted filter paper provides a better seal to a glass funnel than a filter paper cone.

Q4:

What is the main disadvantage of using a larger funnel for a gravity or a vacuum filtration?

  • AMore product adheres to the funnel, making it difficult to retrieve.
  • BSolvent flows through the funnel more slowly, increasing the time needed to complete the filtration.
  • CMore solvent is needed to wash the product effectively.
  • DThe funnel is more difficult to handle, increasing the chance of breakages when the apparatus is assembled.
  • EThe funnel is more difficult to clean after the filtration is complete.

Q5:

Which of the following physical processes is not likely to be observed in the filtrate during a vacuum filtration?

  • AMelting
  • BPrecipitation
  • CFoaming
  • DBoiling
  • EFreezing

Q6:

When a Büchner filtration is complete, in which order should the following actions be performed?

  1. Turn off aspirator.
  2. Disconnect aspirator from flask.
  3. Collect filtered solid.
  • A2, 1, 3
  • B3, 1, 2
  • C1, 2, 3
  • D3, 2, 1
  • E2, 3, 1

Q7:

When collecting a precipitate under suction, which of the following steps is not required?

  • AThe aspirator or vacuum pump is turned off before removing the tubing from the flask.
  • BA clamp is used to secure the Büchner flask.
  • CVacuum is applied using an aspirator or vacuum pump.
  • DThe Büchner flask is attached to the aspirator or vacuum line.
  • EA Büchner or sintered funnel is attached with a ground glass joint or rubber seal.

Q8:

Which of the following pieces of apparatus is not typically used in vacuum filtrations?

  • ACondenser
  • BClamp
  • CAspirator
  • DRubber tubing
  • EBüchner funnel

Q9:

A student performs a gravity filtration using the apparatus shown. In what way has the apparatus been incorrectly assembled?

  • A The flask should be clamped in a lower position.
  • B A sintered funnel has not been used.
  • C The wash solvent should be added using a volumetric pipet.
  • D A stir bar should be added to the filtrate.
  • E The Erlenmeyer flask should be heated.
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