23.1.8 CIA Demonstration: Filtrations

Question 1

CIA Demonstration: Filtrations

Answer 1

• Gravity filtration uses the force of gravity to pull a liquid through a filter.
• Vacuum filtration is much faster than gravity filtration

Question 2

note

Answer 2

• When it is necessary to separate a solid in suspension from a liquid, the easiest method to use is filtration.
• Gravity filtration uses the force of gravity to pull a liquid through a filter.
• First, a piece of round filter paper is folded. Folding increases the surface area of the paper which will be in contact with the funnel.
• The filter is then placed into a funnel, which is placed on top of an Erlenmeyer flask. The filter paper is wetted with distilled water, and the suspension to be separated (iron(III) oxide in water) is added. A rubber policeman is used to guide the suspension into the center of the filter paper.
• The main disadvantage of gravity filtration is that it is often very slow.
• Vacuum filtration is much faster than gravity filtration.
• Vacuum filtration uses a vacuum flask, which has a side arm that can be attached to a water aspirator. The water aspirator creates a partial vacuum by running water past the side arm.
• Vacuum filtration also uses a special funnel called a Büchner funnel. The Büchner funnel runs through a rubber stopper, which creates a seal between the funnel and the vacuum flask.
• A small piece of round filter paper is placed flat in the Büchner funnel and wetted with distilled water. Once a vacuum is established, the suspension to be separated (iron(III) oxide in water) is transferred to the center of the filter paper in the Büchner funnel. Using vacuum filtration, the liquid (water) is quickly removed from the solid (iron(III)oxide). The air movement created by the vacuum also helps to dry the solid.
• When the filtration is complete, the vacuum must be broken at the vacuum flask before turning off the water—otherwise, water can flow back into the flask.