 |
 |
2 of 15 |  |
 |
 |
A-2
EXPERIMENTAL METHOD
Copper metal will be weighed out on the analytical balance in the laboratory. Your laboratory instructor will
show you the correct weighing technique that is to be used in this course. In the fume hood, you will add
nitric acid to the copper metal, and form copper(II) nitrate. The other products of this reaction are nitrogen
monoxide (NO) and water.
Copper(II) carbonate will be prepared by the addition of sodium carbonate (Na2CO3) to the copper(II)
nitrate. Note that an excess of Na2CO3 is used (see Advance Study Assignment, question #2). The excess
Na2CO3 is needed to ensure that any unreacted nitric acid from Part I is neutralized. Copper(II) carbonate
is insoluble in water; it is the precipitate formed when sodium carbonate reacts with copper(II) nitrate.
Copper(II) carbonate is separated from solution by vacuum filtration. You will then wash the copper(II)
carbonate with water which will remove any water soluble impurities by washing them into the filtrate.
The filtrate is the liquid that passes through the filter paper into the filter flask. Because copper(II)
carbonate is very insoluble in water, the filtrate should be nearly colorless.
Copper(II) sulfate (CuSO
4
) is prepared by reacting copper(II) carbonate with sulfuric acid (H2SO
4
). As
you will crystallize the copper(II) sulfate in the last step of the experiment, only a very small amount of
water is added. If too much water is present, the solution will not be saturated and the copper(II) sulfate
will not crystallize. During the addition of H2SO
4
, there will be considerable evolution of a gas. What is this
gas?
The grade for your copper(II) sulfate crystals will be included in your mark for
Experiment A. You will use this copper(II) sulfate as the starting material in Experiment B.
In this experiment, you will use several methods to drive the reactions to completion. These methods
include the use of excess of one or more reagents, formation of a gas that escapes from solution and
formation of a precipitate. It is important to use the amount of each reagent specified in the experiment and
to become familiar with the equipment described in the procedure.
Your laboratory instructor is present to answer any questions. Because some of the chemical reagents are
potentially dangerous, it is necessary for you to take care that you do not splash or spill chemicals on
yourself or your neighbors. In this course, you must wear your safety glasses at all times in the
