Name:
Partners:
It’s time for the Copper Cycle Lab!
Per:
Beaker Code: _______________
The purpose of this laboratory procedure is to: illustrate different types of chemical reactions; show how a quantity of an
element can be carried through a series of chemical transformations without significant loss of mass, thereby illustrating
the law of conservation of matter; and to provide you with experience in fundamental laboratory procedures such as
transferring a reagent form a reagent bottle, transferring a solution or a solid from one vessel to another, decanting,
filtering, drying, washing, and dissolving a precipitate.
You will receive a pre-weighed quantity of copper metal and carry out the following chemical transformations: copper to
cupric nitrate to copper (II) hydroxide to cupric oxide to copper (II) chloride to cupric phosphate to copper (II) sulfate and
back to copper. When you have completed all of the transformations the amount of copper metal you recover should,
theoretically, be equal to the amount of copper metal you started with. The procedures will take approximately four class
days. You will not be told how much copper you began with until you have completed the entire lab and have measured
the amount of copper you ended with.
To ensure that you understand what you will be doing each day, you will begin each session by making sure that you have
correctly balanced equations to work with and on days one and two by predicting how much precipitate should be in your
filter paper at the end of the day (based upon some made-up amount of stuff you began the day with). At the end of the
lab, of course, you will calculate your percent error for the entire lab. Your grade for this lab will be based partially on how
small your percent error is.
In Part A, copper metal is oxidized by nitric acid to produce a blue solution containing cupric nitrate and water and
nitrogen dioxide, a brown, poisonous gas.
Equation A:
In Part B, the blue cupric nitrate solution reacts with sodium hydroxide in a double replacement reaction to produce a
blue precipitate of cupric hydroxide and sodium nitrate.
Equation B:
In Part C, the blue cupric hydroxide solid is decomposed with heating into black cupric oxide solid and water.
Equation C:
In Part D, the black cupric oxide undergoes an acid-base neutralization reaction with hydrochloric acid to form a green
cupric chloride salt solution, and water.
Equation D:
Part E involves a double replacement reaction between the cupric chloride and sodium phosphate to produce a blue
precipitate of cupric phosphate and sodium chloride.
Equation E:
Part F involves another acid-base neutralization reaction as sulfuric acid dissolves the cupric phosphate to produce a blue
cupric sulfate solution and phosphoric acid.
Equation F:
The final reaction in Part G involves the replacement of a less active metal (copper) by a more active mental (zinc). Zinc
is reacted with the cupric sulfate forming zinc sulfate and copper.
Equation G:
Name_____________________________________________ Period #_______Cu Beaker Code____________
For each step (A-G) of the copper lab, answer the following questions:
a) After Part A, the copper will be in the form of _______________ (molecular formula with state) and will look
____________(color).
b)
Draw what’s occurring during the reaction at a microscopic level.
c)
What type of reaction is this?
__________________________________________________________
d)
What is the driving force in this reaction?
__________________________________________________________
e) If you started with 1.583 g of the copper containing substance at the beginning of reaction A, how many grams of the copper
containing substance are you going to end up with at the end of the reaction A? Show your Calculations Below:
a) After Part B, t the copper will be in the form of _______________ (molecular formula with state) and will look
____________(color).
b)
Draw what’s occurring during the reaction at a microscopic level.
c)
What type of reaction is this?
__________________________________________________________
d)
What is the driving force in this reaction?
__________________________________________________________
e) If you started with 1.583 g of the copper containing substance at the beginning of reaction A, how many grams of the copper
containing substance are you going to end up with at the end of the reaction B? Show your Calculations Below:
a) After Part C, t the copper will be in the form of _______________ (molecular formula with state) and will look
____________(color).
b)
Draw what’s occurring during the reaction at a microscopic level.
c)
What type of reaction is this?
__________________________________________________________
d)
What is the driving force in this reaction?
__________________________________________________________
e) If you started with 1.583 g of the copper containing substance at the beginning of reaction A_, how many grams of the copper
containing substance are you going to end up with at the end of the reaction C? Show your Calculations Below:
a) After Part D, the copper will be in the form of _______________ (molecular formula with state) and will look
____________(color).
b)
Draw what’s occurring during the reaction at a microscopic level.
c)
What type of reaction is this?
__________________________________________________________
d)
What is the driving force in this reaction?
__________________________________________________________
e) If you started with 1.583 g of the copper containing substance at the beginning of reaction A, how many grams of the copper
containing substance are you going to end up with at the end of the reaction D? Show your Calculations Below:
a) After Part E, the copper will be in the form of _______________ (molecular formula with state) and will look
____________(color).
b)
Draw what’s occurring during the reaction at a microscopic level.
c)
What type of reaction is this?
__________________________________________________________
d)
What is the driving force in this reaction?
__________________________________________________________
e) If you started with 1.583 g of the copper containing substance at the beginning of reaction A, how many grams of the copper
containing substance are you going to end up with at the end of the reaction E? Show your Calculations Below:
a) After Part F, the copper will be in the form of _______________ (molecular formula with state) and will look
____________(color).
b)
Draw what’s occurring during the reaction at a microscopic level.
c)
What type of reaction is this?
__________________________________________________________
d)
What is the driving force in this reaction?
__________________________________________________________
e) If you started with 1.583 g of the copper containing substance at the beginning of reaction A, how many grams of the copper
containing substance are you going to end up with at the end of the reaction F? Show your Calculations Below:
a) After Part G, the copper will be in the form of _______________ (molecular formula with state) and will look like
____________(color).
b)
Draw what’s occurring during the reaction at a microscopic level.
c)
What type of reaction is this?
__________________________________________________________
d)
What is the driving force in this reaction?
__________________________________________________________
e) If you started with 1.583 g of the copper containing substance at the beginning of reaction A, how many grams of the copper
containing substance are you going to end up with at the end of the reaction G? Show your Calculations Below:
Questions to be answered when lab is completed:
1) What will happen if the copper is overheated during the drying process? How will this affect the percent of copper that you
will recover?
2) Comment on the physical appearance of the reclaimed copper at the end of Reaction G. How could it be made to look more
like the original copper?
3) List possible experimental errors that might lead to a mass of reclaimed copper less than that originally used.
4) List possible experimental errors that might lead to a mass of reclaimed copper greater than that originally used.
5) Why was it essential to have stochiometric (balanced) equations to work with in this lab?
YOU NEED DATA FROM FINAL WEIGH IN on the last day to complete the following:
WHAT WAS YOUR GROUP’S FINAL MASS OF copper:
______ = “GOT”
6) What mass of Cu should you have gotten?
______ = “Shoulda”
7) What was your Cu Team’s % error?
Calculations Shown Below:
_____ = %error
8) Is this percent error good or bad? Why?
Procedure:
Copper to Copper Day 1: A—C
Part A—Preparation of Cupric Nitrate by Oxidation of Copper with Nitric Acid
1. Place the beaker containing the copper in a fume hood. Use a Beral-type pipette to carefully add 5 ml
of 8 M HNO3 drop-wise to the beaker. Caution: Nitric acid is severely corrosive. Be sure to wear
chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron.
2. Warm the beaker gently on a hot plate set on low until the copper is completely dissolved. If
necessary, add a few more drops of 8 M HNO3 to dissolve any remaining copper. Caution: The
brown fumes released are poisonous; do not remove the beaker from the fume hood until all of the
copper is reacted and no more gas is released. Do not breathe the brown gas.
3. Dilute the solution in the beaker with 10 ml of distilled water.
Part B—Preparation of Cupric Hydroxide from Cupric Nitrate
4. To the solution from Part A, add 5 ml of 8 M NaOH with a disposable pipet while constantly stirring.
5. Allow the precipitate (solid) to settle a bit. Test for complete precipitation by adding 1 more drop of 8
M NaOH to the clear supernatant liquid. If no additional precipitate forms, the reaction is complete. If
additional precipitate does form, add more 8 M NaOH, drop wise, until precipitation is complete. If
you are unsure if more precipitate forms, add water until two distinct layers form then test as
described above.
6. Test the pH of the liquid by touching a stirring rod first to the solution and then to a piece of 1-12 pH
paper. The liquid should be basic, turning the pH paper to blue. Since the solution itself is blue, be
sure to look at the liquid as it touches the paper. If the solution is not basic, add more 8 M NaOH
drop by drop until it is basic.
Part C-Preparation of Cupric Oxide from Cupric Hydroxide by Decomposition
7. To the mixture from Part B, add enough distilled water to give the beaker a total volume of about 100
ml.
8. Using a hot plate, heat the mixture gently (level 5-6), stirring constantly, until the mixture turns a
different color.
9. Prepare a filtration setup. Carefully fold a piece of filter paper and fit it into a clean funnel. Moisten
the filter paper so that it fits snugly into the funnel. Test the filtration system with a small amount of
water to be sure the water flows freely and rapidly.
10. Filter the mixture. Do not add so much solution into the filter that it raises over the sides of the filter
paper. Wash any traces of solid from the beaker using a stream of water from a wash bottle. Make
sure to occasionally empty the filtrate (the solution inside of the flask below the funnel) as long as
there is no Copper in it.
11. If there is Copper in the filtrate, empty it into your beaker and re-filter the solution.
12. Wash the solid precipitate in the filter paper twice with hot distilled water. To do this, add enough
water to completely cover the precipitate and allow it to run through.
13. Discard the filtrate as instructed. Leave the product in the filter paper to dry overnight if possible.
Copper to Copper Lab Day 2: D-E
Part D—Preparation of Cupric Chloride form Cupric Oxide
14. Place the filter paper with the precipitate from Part C in a funnel. Place your cleaned 250-ml beaker
below the funnel.
15. Dissolve the solid in the filter paper by carefully pipetting 8 ml of 6 M HCl directly into the funnel.
Allow the resulting solution to run into the beaker.
16. If the solid does not completely dissolve when the HCl runs through the filter the first time, the liquid
that has run through should be squirted back through the filter using a pipette. This process should
be repeated until ALL the solid has dissolved completely.
17. When the solid is completely dissolved, the filter should be washed twice, until all of the color has
been washed out of the filter paper, with a minimal amount of cold distilled water. The washing
should be allowed to run into the beaker with the solution.
Part E—Preparation of Cupric Phosphate from Cupric Chloride
18. Neutralize the solution by first adding 8 M NaOH, drop by drop with constant stirring, until the liquid in
the beaker acquires a lasting cloudiness (one that does not dissolve with stirring).
19. Then add 6 M HCl, drop by drop with constant stirring, just until the cloudiness disappears.
20. Add 15 ml of 0.3 M Na3PO4 slowly and with constant stirring. Observe precipitate formation.
21. Allow the precipitate to settle a bit. Test for complete precipitation by adding 1 more drop of 0.3 M
Na3PO4 to the liquid. If no additional precipitate forms, the reaction is complete. If additional
precipitation does occur, add more 0.3 M Na3PO4 drop wise until precipitation is complete. If you are
unsure if more precipitate forms, add water until two distinct layers form then test as described above.
22. Using a hot plate, very carefully heat the solution while stirring constantly at low heat (level 4-5) until
it just begins to show signs of boiling. This will make filtration easier by helping to consolidate the
precipitate. Do not allow the mixture to boil vigorously. If it turns black, return to the steps
in part C.
23. Prepare a filtration setup as done previously. (See Step C if you need a reminder).
24. Filter the mixture. Do not add so much solution into the filter that it raises over the sides of the filter
paper. Wash any traces of solid from the beaker using a stream of water from a wash bottle.
25. Wash the solid precipitate in the filter paper twice with hot distilled water. To do this, add enough
water to completely cover the precipitate and allow it to run through.
26. Discard the colorless filtrate as instructed. Leave the product in the filter paper to dry overnight if
possible.
Copper to Copper Lab Day 3: F-G
Part F—Preparation of Cupric Sulfate from Cupric Phosphate
27. Place a cleaned 250-ml beaker below the funnel from Part E containing the precipitate.
28. Dissolve the solid by carefully pipetting 12 ml of 2M H2SO4 directly into the funnel. Allow the resulting
solution to run into the beaker.
29. If the solid does not completely dissolve when the H2SO4 runs through the filter the first time, the
liquid that has run through should be recycled and re-pipetted through the filter. This should be
repeated until ALL the solid completely dissolves.
30. When the solid is completely dissolved, the filter should be washed twice with a minimal amount of
cold distilled water, until all of the color is gone from the filter paper. The washings should be allowed
to run into the beaker with the solution.
Part G—Preparation of Copper from Cupric Sulfate
31. To the solution form Part F, add about 2 grams of mossy zinc.
32. Allow the solution to stand, with occasional stirring, until it is entirely colorless. This indicates that all
of the copper has been removed from solution. If absolutely necessary, add more zinc to the solution.
33. Once the solution is colorless, the excess zinc must be removed.
a. Large pieces can be removed with plastic tweezers. Rinse back into the beaker any copper that
clings to the solid Zn with a wash bottle.
b. Very small pieces should be dissolved. To do this, add 2 M H2SO4 in 1-ml portions while stirring
until the excess zinc is completely dissolved. Warm the solution to speed the rate of reaction.
Complete dissolution of zinc will be indicated by the fact that the precipitate is uniformly
copper-colored and no more hydrogen gas bubbles are produced.
34. Allow the copper to settle. Decant off and discard the supernatant liquid. In the process of decanting,
the liquid is carefully poured off while the solid remains behind. To avoid loss of solid, the liquid is not
drained off completely; some is allowed to remain behind with the solid.
35. Wash the copper in the beaker three times with cold distilled water. To do this, add about 20 ml of
water to the precipitate in the beaker. Stir thoroughly with a stirring rod, allow the precipitate to
settle, and decent off the supernatant clear liquid. Repeat this two more times.
36. Weigh a clean, dry filter paper.
37. Prepare a filtration setup as done previously. (See Step C if you need a reminder).
38. Filter the mixture. Do not add so much solution into the filter that it raises over the sides of the filter
paper. Wash any traces of solid from the beaker using a stream of water from a wash bottle.
39. Dry the copper overnight. If desired during class you can dry the copper under a heat lamp.
40. Weigh the filter paper and the copper.