Chemistry Lab Filtering Technique

Objective:

The purpose of the lab is to learn filtering techniques. Specifically, to form and filter a calcium carbonate precipitate using a Buchner funnel.

Procedure:

a.) Prepared a mixture of .5 M calcium nitrate (45 mL) and .01 M sodium carbonate by combining and stirring the two liquids in a beaker. Allow the mixture to stand.

b.) Prepare the filtration assembly. The assembly consists of a tapered flask with a buchner funnel inserted in the top. The funnel has a rubber stopper attached to its stem in order to properly fit into the flask. The flask has a stem with a hose that is attached to a vacuum so that suction can be applied during filtering.

c.) Place a filter on a clean dry watch glass. Weigh the two items together and record the value.

d.) Place the filter in the Buchner funnel. Wet the filter with distilled water so it sticks to the bottom of the funnel.

e.) After the mixture from part (a) has separated, turn on the suction valve and then slowly pour the mixture through the filter in the Buchner funnel. Be sure to completely empty the beaker (use distilled water if necessary to wash the precipitate from the beaker).

f.) Wash the precipitate in the filter with two 20-mL portions of distilled water. Allow the suction to continue for several minutes.

g.) When the precipitate appears to be dry, turn off the suction and carefully remove the filter and precipitate and place them on the clean dry watch glass.

h.) Place the glass with the filter and precipitate under a heating lamp for approximately 15 minutes.

i.) Weigh the watch glass, filter, and precipitate and record the value.

j.) Repeat steps (h) and (i) until the weight remains constant.

Results and Discussion:

The measurements obtained from the experiment are as follows:

1st 2nd 3rd 4th 5th

Mass of glass, filter, and precipitate (g) 68.34 68.18 68.14 68.11 68.11

Mass of glass and filter only (g) 65.77 65.77 65.77 65.77 65.77