ChemLab #35 - Transformations of Copper
Date of Lab:   Teacher's Lab Score:
Lab Group Members:
 
The Lab Problem: Transform copper metal into ions and back to copper metal: a guided discovery.
Research References:   You will use knowledge and skills from chemistry class this year to work your way through this process.
DAY 1 - Conversion 1: Change elemental copper to copper (II) nitrate.
Pre-lab Assignment
Copper metal reacts with nitric acid to produce aqueous copper (II) nitrate, nitrogen dioxide gas, and water.

1. Write a balanced equation for the reaction.

 

 

2. If 1.48 g of copper are used, how many moles of copper (II) nitrate should be produced?

 

 

 

Day 1 Procedure
  1. Obtain between 0.5 g and 0.8 g of copper metal. Record in Data Table 1.
  2. Place the copper in 250 ml beaker and add 20 ml 1 M HNO3. The acid must cover all the copper metal.
  3. Immediately place a watch glass on top of the beaker.
  4. Record your observations below.
  5. Place the beaker on a lab tray overnight.
Observations from procedure

 

 

Data Table 1

 

Original amount of Copper:

 

pH of Cu(NO3)2 solution:

 

pH of 6M NaOH:

 

pH of NaOH + Cu(NO3)2 solution:

 

Mass of filter paper:

 

Mass of filter paper and Copper product:

 

*Mass of copper product:

 

Mass of Theoretical Yield:

 

*% Yield of Copper:
 

 
DAY 2 - Conversion 2: Change copper (II) nitrate to copper hydroxide.
Pre-lab Assignment Part 1
A precipitation reaction reaction occurs with aqueous copper (II) nitrate and aqueous sodium hydroxide.

1. Write a balanced equation for the reaction.

 

 

2. How many grams of the solid product are produced from 0.0233 moles of copper (II) nitrate?

 

 

 

Day 2 Procedure Part 1
  1. Test the pH of the Cu(NO3)2 solution by placing a drop on pH paper. Record in Table 1.
  2. Pour 20 ml of 6M NaOH into a graduated cylinder. Test the pH by placing a drop on pH paper. Record in Table 1.
  3. Put the 250 ml beaker with Cu(NO3)2 solution inside a 600 ml beaker half full of cold water. (this serves as a cooling bath)
  4. SLOWLY pour the 6 M NaOH into the Cu(NO3)2 solution. Stir and check with pH paper. The resulting solution must be basic. Record in Table 1.
Observations from procedure

 

 

Day 2 - Conversion 3: Change copper hydroxide to copper oxide.
Pre-lab Assignment Part 2
When heated, solid copper (II) hydroxide decomposes into solid copper (II) oxide and water.

1. Write a balanced equation for the reaction.

 

 

2. How many grams of solid product are produced from 4.37 g of copper (II) hydroxide?

 

 

 

Day 2 Procedure Part 2
  1. Add 100 ml of distilled water to the beaker.
  2. Heat the solution to a GENTLE boil. Continue to boil until no more color change is observed.
  3. Allow to cool for 5 minutes.
  4. Decant (pour off) the CLEAR LIQUID.
  5. Wash the precipitate by adding 100 ml of distilled water.
  6. Allow the precipitate to settle over night.
Observations from procedure

 

 

 
DAY 3 - Conversion 4: Change copper oxide to copper (II) chloride and water.
Pre-lab Assignment Part 1
Solid copper (II) oxide reacts with hydrochloric acid to produce aqueous copper (II) chloride and water.

1. Write a balanced equation for the reaction.

 

 

2. If 1.85 g of copper (II) oxide reacts with 0.05 moles of hydrochloric acid, which reactant would be limiting and which would be in excess?

 

 

 

3. How many moles of copper (II) chloride can be produced?

 

 

 

Day 3 Procedure Part 1
  1. Decant the clear liquid.
  2. Add 50 ml of 6 M HCl to the black CuO in the beaker.
  3. Stir for several minutes.
Observations from procedure

 

 

Day 3 - Conversion 5: Change copper (II) chloride to elemental copper.
Pre-lab Assignment Part 2
Aqueous copper (II) chloride reacts with aluminum metal to produce copper metal and aqueous aluminum chloride.

1. Write a balanced equation for the reaction.

 

 

2. What is the theoretical yield (in grams) of solid copper if 0.0233 moles of copper (II) chloride react with excess aluminum metal.

 

 

 

3. What is the percent yield if a student produced 1.13 grams of copper in the lab?

 

 
Day 3 Procedure Part 2
  1. Add a piece of aluminum wire bent into the shape of an "L" to the CuCl2 solution.
  2. Dislodge the copper from the wire. (do not remove the Al wire)
  3. Cover the beaker with a watch glass and place on a lab tray over night.
Observations from procedure

 

 

 
DAY 4 - Procedure:
  1. Remove the excess aluminum wire with forceps.
  2. Decant the CLEAR liquid.
  3. Wash the copper in the beaker three times with 50 ml each of HOT distilled water. Allow the precipitate to settle after each wash and decant.
  4. Weight a piece of filter paper. Record in Table 1.
  5. Add 50 ml of hot water to the beaker and filter the product.
  6. With a distilled water wash bottle, rinse all remaining copper metal from the beaker into the filter funnel.
  7. WHEN ALL BURNERS ARE PUT AWAY, wash the copper with a small amount of acetone.
  8. Place the washed copper and filter paper on a watch glass on a lab tray over night.
 
DAY 5 - Procedure:
  1. Weigh the dried sample and record in Table 1.

Final Questions:

  1. What is the theoretical yield of copper, the amount of copper that should be in the dried sample?
     
     
  2. Calculate the actual yield of copper.*
     
     
     
  3. Calculate the percent yield of copper.*
     
     
     
  4. There are many times during this experiment where copper might have been lost. Identify at least two of these.
     
     
     
  5. What kind of error would result in the final amount of copper being greater than the theoretical amount?