EXPERIMENT 3

1
EXPERIMENT 3

• A SEQUENCE OF COPPER REACTIONS

2
PURPOSE

• To use a cycle of copper reactions to illustrate
  several common reactions and laboratory
  techniques.

3

• Before coming to the laboratory, make sure you
  have calculated the volume or weight of each
  reagent required in the experiment for your
  assigned value of copper.

• Fill in the Data and Observation sheet where
• indicated, including the volume or weight of
• a. 8.0 M HNO3
• b. 4.0 M NaOH
• c. 1.0 M H2SO4
• d. solid zinc (calculate the weight required)

4
Obtain the weight of the copper sample by
difference, recording all weights to 0.01 g.
1. Weigh the vial copper.
Label a 150 mL beaker with your station number.
5
2. Transfer the copper to the beaker.
3. Re-weigh the empty vial
4. Obtain the weight of Cu by difference.
6
Keeping the beaker under the ventilation hood,
carefully pour about 5 mL HNO3 (8.0 M) into the
beaker containing the copper. The acid should
just cover the bottom of the beaker.
7
Leave the beaker under the hood and do not
proceed until all the copper has dissolved and
brown NO2 fumes are no longer evolved. Once this
is the case, add 10 mL H2O.
8
To obtain an accurate reading, you should be at
eye level with the meniscus (i.e. your line of
sight should be parallel with your reading).
9
Use the stirring rod to direct the addition of
water (or any other solvent) to your solution.
10
Keeping the beaker under the ventilation hood,
slowly add 15 mL of 4.0 M NaOH.
ATTENTION! Whenever you pour a reagent, keep
your hand over the label of the container.
CAUTION! The neutralization of concentrated HNO3
is an exothermic reaction and spattering may
occur.
11
If the solution is not strongly basic add more
NaOH.
Check the pH by dipping a stirring rod into the
solution and touching it to pH paper.
With completion of this step the solution can be
removed from under the hood.
12
Add 25 mL H2O and 2 boiling chips to the beaker.
Heat to boiling. Hold the beaker on the hot plate
with tongs and stir CONSTANTLY!
13
When all Cu(OH)2 has been converted to black CuO,
remove the beaker from the heat, place it on a
paper towel, and let the precipitate settle.
There should be no blue colour remaining.
14
Lab stand and clamp
Büchner funnel
Connect to the vacuum.
Filter flask
Set up the vacuum filtration apparatus.
15
Place a filter paper of the correct size on the
Büchner funnel and wet it with water.
16
For vacuum, move the lever to the down position
17
Decant the excess liquid into the funnel first,
then make a slurry of CuO and the remaining
liquid, and pour it into the funnel in one motion.
18
Place the filtered CuO and filter paper into the
150 mL beaker.
Measure 15 mL of 1.0 M H2SO4 into a graduated
cylinder and use small portions of this acid to
rinse any remaining CuO from the funnel into the
beaker.
Add the remaining acid to the beaker and stir to
dissolve all CuO.
19
Continue to stir the solution until no more black
CuO is visible, and the solution is blue.
20
Empty and wash the filter flask, and fit a
culture tube into the flask to catch the filtrate
(CAUTION! Make sure the liquid does not overflow).
Filter the solution to remove the filter paper
and boiling chips.
21
1. Tare an empty 250 mL beaker on the balance.
1
2. Add granular zinc to obtain between 0.80 - 1.0
grams
2
22
1. Pour the copper solution into the beaker
containing the zinc.
1
2. Put the solution under the hood while H2 gas
is being evolved.
2
23
Stir occasionally until the solution is
colourless.
24
Test for completion of the reduction reaction as
described in your laboratory manual.
25
Filter the copper granules by vacuum filtration
on the Büchner funnel wash 2-3 times with
distilled water, then with acetone.
Allow the copper to dry under suction for several
minutes.
26
Remove the copper to dry further on a large
filter paper placed on paper towels.
Determine the weight of copper obtained by
pre-weighing the empty glass vial, placing the
copper into the vial and then re-weighing the
vial plus copper.
Submit the copper sample to your TA in the vial
labeled with your name, day, group and station
number.