Chapter 9 Laboratory: Introduction to Chemical Reactions and Stoichiometry 177
Carefully remove the filter paper from the funnel and set
it aside to dry. You can speed drying by placing the filter
paper and product under an incandescent lamp or by
drying it gently in an oven at the lowest heat setting.
Weigh the evaporating dish and record its mass to 0.01 g
on line F of Table 9-4.
Place the evaporating dish on the hotplate, transfer as
much of the filtrate as the dish can comfortably contain,
and turn the hotplate on, set to low heat. As the solution
in the dish evaporates, transfer more of the filtrate until
all of it has been transferred to the dish. Finally, rinse
the receiving beaker with a few mL of water, and transfer
the rinse water to the evaporating dish. When the liquid
in the evaporating dish is nearly gone, watch the dish
carefully and continue heating until the solution has
been evaporated to dryness.
While you are waiting for the copper(II) hydroxide and
sodium sulfate to dry, calculate the expected masses
for both of them based on the initial masses of the
copper(II) sulfate and sodium hydroxide. (Remember
that one mole of copper(II) sulfate reacts with two
moles of sodium hydroxide, and remember to determine
the limiting reagent before you calculate the expected
masses.) Enter the expected masses of copper(II)
hydroxide and sodium sulfate on lines G and H of Table
9-4, respectively.
When the copper(II) hydroxide is dry, weigh the filter
paper and product, and record their mass to 0.01 g on
line I of Table 9-4. Subtract the mass of the filter paper
(line E) from the combined mass of the filter paper and
product (line I) to determine the mass of copper(II)
hydroxide, and record that value to 0.01 g on line J of
Table 9-4.
When the sodium sulfate is dry, weigh the evaporating dish
and product, and record their mass to 0.01 g on line K of
Table 9-4. Subtract the mass of the evaporating dish (line
F) from the combined mass of the evaporating dish and
product (line K) to determine the mass of sodium sulfate,
and record that value to 0.01 g on line L of Table 9-4.
Calculate the actual percent yields of copper(II)
hydroxide and sodium sulfate, and enter those values on
lines M and N of Table 9-4, respectively.
FIGURE 9-5: The precipitate of copper(II) hydroxide
TABLE 9-4: Stoichiometry of a double displacement reaction—
observed and calculated data
Item Data
A. Mass of copper sulfate
pentahydrate
______.______ g
B. Moles of copper sulfate
pentahydrate
____.________ moles
C. Mass of sodium hydroxide ______.______ g
D. Moles of sodium hydroxide ____.________ moles
E. Mass of filter paper ______.______ g
F. Mass of evaporating dish ______.______ g
G. Expected mass of copper(II)
hydroxide
______.______ g
H. Expected mass of sodium sulfate______.______ g
I. Mass of filter paper + copper(II)
hydroxide ______.______ g
J. Actual mass of copper(II)
hydroxide (I – E) ______.______ g
K. Mass of evaporating dish + sodium
sulfate
______.______ g
L. Actual mass of sodium sulfate (K
______.______ g
M. Percent yield of copper(II)
hydroxide (100 · J/G)
__.__ %
n. Percent yield of sodium sulfate
(100 · L/H) ______.______ %
13.
14.
15.
16.
17.
18.
19.
