Chapter 7 Laboratory: Solubility and Solutions 143POCEDURER
CUTIOA nS:
Copper sulfate is moderately toxic by ingestion or
inhalation and is irritating to eyes and skin. Wear splash
goggles, gloves, and protective clothing at all times.z
PRTI: A mA kE UpREfERENCE SoLUTIoNS
If you have not already done so, put on your splash
goggles, gloves, and protective clothing.
Label six test tubes #1 through #6.
Use the 5.00 mL pipette to transfer 10.00 mL of distilled
water into test tube #1, and 5.00 mL of distilled water
into each of the other five test tubes.
Place a weighing paper on the balance and tare the
balance to read 0.00 g.
Weigh out about 2.40 g of copper sulfate, record the
mass to 0.01 g on line A of Table 7-2 under “Test tube #1,”
and transfer the copper sulfate to test tube #1.
Swirl test tube #1 until all of the copper sulfate
has dissolved.
Use the 5.00 mL pipette to transfer 5.00 mL of the
copper sulfate solution from test tube #1 to test tube #2.
Swirl test tube #2 until the distilled water and copper
sulfate solution is thoroughly mixed.
Repeat steps 7 and 8 for test tubes #3, #4, and #5.
When you finish, each of the five test tubes should
contain a solution of copper sulfate at half the
concentration of the preceding tube. Test tube #1 should
have an intense blue color, with each succeeding test
tube a paler blue.
Calculate the mass of copper sulfate in each of the tubes
#2 through #5 and the mass-to-volume percentage of
tubes #1 through #5, and enter those values in lines A and
B of Table 7-2.
This laboratory has two parts. In Part I, we’ll make up solutions
that contain known concentrations of copper sulfate. In Part
II, we’ll make up a solution with an unknown concentration of
copper sulfate and estimate the concentration of that unknown
solution using visual colorimetry.
dISpoSAL: Copper sulfate solutions may be neutralized
with sodium carbonate and the precipitate can then be
disposed of with household waste. Alternatively, small
amounts of copper sulfate solution may be flushed down
the drain. (Copper sulfate is, after all, sold as root killer,
for which purpose it is—you guessed it—flushed down
the drain.)TABLE 7-2:
Determine concentration of a solution by visual colorimetry (standard solutions): observed and calculated data
Item Test tube #1Test tube #2Test tube #3Test tube #4Test tube #5A. mass of
copper sulfate___._________ g___._________ g___._________ g___._________ g___._________ gB. mass-
to-volume
percentage____.________%____.________%____.________%____.________%____.________%