CYCLE OF COPPER REACTIONS
NOTE: You must wear goggles and aprons throughout this experiment!! Follow all directions carefully!!
In this lab you will weigh a sample of copper metal and react it with nitric acid to form copper(II)nitrate.
From this blue solution, you will precipitate copper(II) hydroxide. Then, by thermal decomposition, the black
copper(II) oxide will be formed. The addition of sulfuric acid will produce copper(II)sulfate, from which you will
precipitate copper metal by displacement with zinc. From the initial weight and the final weight of the copper before
and after the reactions you will be able to determine a quantitative relationship between the reactants and the
products.
The numerous reactions in this lab will provide you with practice writing formulas and equations. The
quantitative relationships between the reagents will provide an experimental basis for balancing equations and for
the concept of conservation in a chemical reaction.
PROCEDURE:
1. Obtain a clean dry 400 ml beaker. Do all steps in this beaker.
2. Obtain a small 50 ml beaker (the product in step #8 will be dried in this beaker). Mark it with your
name with a lead pencil. Weigh it to the nearest 0.01 gram and set it aside.
3.
4
Carefully weigh around 0.50 grams of copper filings and place it in the 400 ml beaker. Record all
weights!!
Place your beaker in the fume hood and then add 4.0 ml concentrated HNO3. Caution: Nitric acid is
extremely dangerous. Handle with care!! The reddish brown fumes that are produced in this
step, NO2, are toxic. Keep the beaker in the hood until the gas is no longer evolved. (It helps to swirl
the liquid to drive the gas out.) When the reaction is complete, add about 125 ml distilled water and
then carry the beaker to your lab station. Observe and record the characteristic color of the copper(II)
solution. Record all observations of changes throughout this lab.
5
Add 30 ml of 3.0 M NaOH. Caution: NaOH is very corrosive. Handle with care!! The precipitate
that forms is copper(II) hydroxide.
6
Add a boiling chip to your solution. Heat, with stirring to prevent spattering, until the solution
boils. The black precipitate formed by thermal decomposition is copper(II) oxide. Let the solution
settle. Decant the supernatant liquid (it can go down the sink). To rinse the precipitate, carefully add
about 200 ml boiling water (in large beakers on hot plates). Let the solution settle and decant once
more. Cool.
7
In the fume hood, add 15 ml of 6.0 M H2SO4 (caution: this is very corrosive) to convert the CuO to
CuSO4. Remove boiling chip with tweezers.
8
In the fume hood, add 2.5 g of zinc granules to precipitate the copper metal. Stir until the supernatant
liquid is colorless and no more gas bubbling is observed. When the reaction is completed, return to
your lab station and decant the solution down the sink. Using a rubber policeman and a little distilled
water, transfer the solid to the small, labeled and massed beaker from step 1. Finish the next step in
this beaker.
9
Return to the fume hood. Add 5 ml of water, then 10 ml concentrated HCl (dangerous!!) to react with
and remove any zinc metal left over. When no more bubbling is apparent, return to your station and
decant the acid into the sink, flushing with lots of water. Add water to your beaker, stir, let settle,
then decant. Repeat washing the product with water. Finally, wash your product with 5 ml ethanol, let
settle, and decant the liquid into the sink. Place your product in the drying oven overnight.
10 Weigh and record the weight of your copper during the next class period. The copper precipitate can
be scraped out and disposed of in a labeled beaker. Clean your small beaker with soap and water.
Cycle of Copper Lab Write-up
1.
For all five reactions listed in your observation table that include copper:
a. Write a word reaction.
b. Write a balanced equation, complete with symbols for states of matter: (s), (l), (aq), (g).
The equation for the first reaction is:
Cu(s) + 4HNO3(aq)  Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l) + energy
c.
(This is a reaction type that we have not yet studied.)
Identify the type of reaction for all but the first reaction.
2.
a. Write a balanced equation for the reaction between zinc and hydrochloric acid solution.
b. What type of reaction is this?
c. What was the purpose of this reaction?
3.
Identify the ions dissolved in the solution that you decanted in:
a. Step 6
b. Step 8
c. Step 9
4.
Calculate the percent yield of copper metal (see Formal Lab Report Form)
If your yield is less than 100%, give one best reason for this loss.
If your yield is greater than 100%, give one best reason for this gain.
5.
This experiment involves copper cycling through solid to aqueous to solid states. Explain how this lab
supports the Law of Conservation of Matter.
For Data Book
Purpose: 1. To observe and identify different types of chemical reactions.
2. To write equations for each reaction
Data:
1. Masses:
50 mL beaker ___________ g
Initial copper mass __________g
50 mL beaker + copper product (Day 2) ____________g
Step
4.
2. Reactions
Reactants
Cu(s) + HNO3(aq) 
5.
Cu(NO3)2(aq) + NaOH(aq) 
6.
Cu(OH)2(aq) 
7.
CuO(s) + H2SO4(aq) 
8.
CuSO4(aq) + Zn(s) 
9.
Zn(s) + HCl(aq) 
(notice Cu is not involved in this reaction)
Observations