Lesson

Background

Most metals found on earth are not found in their elemental state, but rather they are combined with one or more other elements. The mixtures of minerals that contain these recoverable metals are called ores. Metal ore is a type of rock from which a metal can be extracted. Ores are most often oxides; a common example is hematite (Fe₂O₃). But metals can also be found in sulfides (like ZnS), sulfates (like BaSO₄), or carbonates—like what you will work with today. Copper can be found in a couple of different ores—one of which is malachite, which contains copper(II) carbonate.

In this lab, you will extract copper from copper carbonate in two different ways, and then determine which industrial method is most effective.

Method #1: Smelting

Smelting involves the use of a high-heat blast furnace and a reducing agent (like coke, which is a form of carbon) to extract the metal. In this case it is a two-stage reaction.

Stage 1: CuCO₃ (s) ⇾ CuO (s) + CO₂ (g)
Stage 2: 2 CuO (s) + C (s) ⇾ 2 Cu (s) + CO₂ (g)

Method #2: Displacement

This method involves dissolving the ore in acid, then adding a cheap, but reactive metal to the solution to replace the copper. The first stage of this reaction occurs in two parts, occurring almost simultaneously. The second stage occurs after adding another metal (in this case, iron), to the solution.

Stage 1:
[part A] H₂SO₄ (aq) + CuCO₃ (s) ⇾ CuSO₄ (aq) + H₂CO₃ (aq)
[part B] H₂CO₃ (aq) ⇾ H₂O (l) + CO₂ (g)

Stage 2: CuSO₄ (aq) + Fe (s) ⇾ FeSO₄ (aq) + Cu (s)

Purpose

To extract copper from copper carbonate in two different ways and determine which industrial method is most effective.

Materials

• Crucible with cover
• Balance
• 1,000-mL and 100-mL beakers
• Bunsen burner
• Ring stand
• Pipe-stem triangle
• Hot plate
• Glass stirring rod
• Crucible tongs
• Copper(II) carbonate
• Charcoal
• 1M sulfuric acid
• Scrap iron

Safety

• Always wear safety goggles when working with chemicals in a laboratory setting.
• Use caution around open flames and use proper safety equipment when working with hot glassware.

Procedure

Part 1: Smelting

1. Record the mass of a clean/dry crucible.
2. Place approximately one gram of copper(II) carbonate in the crucible. Record the mass of copper(II) carbonate.
3. Place the crucible, without the lid, on a pipe-stem triangle (See figure 1)
4. Heat the crucible over a hot flame. Stir the powder with a glass stirring rod until all of it turns black.
5. After all the copper(II) carbonate in the crucible has turned to a black color weigh out one gram of powdered charcoal in a weighing boat. (Charcoal consists mainly of carbon).
6. Turn off the burner and add the charcoal to the crucible. Using a glass rod, stir the two substances in the crucible together until they are thoroughly mixed.
7. Heat the crucible, with the lid on, over a strong flame of the Bunsen burner for 15 min. After 15 minutes, turn the flame off and allow the crucible to cool for 10 minutes.
8. Using crucible tongs, pour the substance from the crucible into a 1000-mL beaker 2/3 full of water. Use the glass rod to scrape the contents out of the crucible and into the beaker. Return the crucible to the pipe-stem triangle to cool.
9. Pour the water out of the beaker, taking care not to lose the solid at the bottom of the beaker. Add about 500 mL of water to the beaker and rinse the material again.
10. Repeat rinsing until only copper is left in the bottom of the beaker.
11. When only copper remains, dump the copper onto a paper towel and dab dry.
12. Record the mass of the copper obtained.

Part 2: Displacement

1. Record the mass of a clean/dry 100-mL beaker.
2. Place approximately one gram of copper(II) carbonate in the beaker. Record the mass of copper(II) carbonate you are using.
3. Add 1M sulfuric acid (H₂SO₄) one dropperful (full pipet-squirt) at time to the beaker. Swirl between each addition. Keep adding until the solution turns turquoise and clear (not cloudy) and stops fizzing. Record the number of dropperfuls you end up using.
4. Add 0.48 g of iron filings to the beaker and stir.
5. Put on the hot plate, medium-high setting, and keep stirring to continue the reaction.
6. Continue heating until all the water has boiled off.
7. Add about 20 mL of water to rinse away impurities and decant into a waste beaker.
8. Heat again until all the water has boiled off.
9. Stir the solid around a little bit and heat for another minute or two to ensure the copper left behind is completely dry.
10. Record the mass of the beaker with dry copper.

Data Table

Construct one for method one and a separate one for method two

Calculations

Method #1: Smelting

1. Convert the mass of CuCO₃ you initially used into moles.
2. According to the coefficients for CuCO₃ and Cu in their balanced equations, there is a 1:1 ratio of between moles of CuCO₃ you start with, and moles of Cu you should be able to produce. This means your answer to the question above also represents the number of moles of Cu you should have been able to produce. Convert this answer to grams of Cu.
3. Your answer above is called a theoretical yield – it represents how much product you theoretically should be able to produce, based on how much reactant you started with. A percent yield is a measure of the efficiency of the reaction – a comparison of how much product you actually produced (actual yield, from your data table) to how much you should have been able to produce (theoretical yield). Calculate your percent yield for this reaction.

The formula is: (actual yield) x 100%
(theoretical yield)

4. Calculate the total cost of the raw materials used for this method.

Helpful Info for Cost Calculations:

CuCO₃: $30.85 for 500g

Charcoal (C): $13.10 for 100g

Method #2: Displacement

1. Convert the mass of CuCO₃ you initially used into moles.
2. The mole ratio of CuCO₃ to Cu in this method is still 1:1, so moles of CuCO₃ = moles Cu. Convert your answer from the question above into grams of Cu.
3. Your answer above is your theoretical yield of copper. Calculate your percent yield.
4. Calculate the total cost of the raw materials used for this method.

Analysis Questions:

1. Identify the type of chemical reaction for each equation in this lab.

METHOD 1 (Smelting)
Stage 1: CuCO₃ (s) ⇾ CuO (s) + CO₂ (g)
Stage 2: 2 CuO (s) + C (s) ⇾ 2 Cu (s) + CO₂ (g)

METHOD 2 (Displacement)
Stage 1:
[part A] H₂SO₄(aq) + CuCO₃(s) ⇾ CuSO₄(aq) + H₂CO₃(aq)
[part B] H₂CO₃ (aq) ⇾ H₂O (l) + CO₂ (g)
Stage 2: CuSO₄ (aq) + Fe(s) ⇾ FeSO₄(aq) + Cu(s)

2. Stage two of both methods involve redox reactions. Identify the elements reduced & oxidized in each reaction.

3. In Stage one of method two, why did bubbles form? What were those bubbles made of?

4. In Stage two of method two, what is the purpose of the iron? Give two examples of metals other than iron that could have been used here, and two examples of metals that would not have worked.

5. Which method gave the highest percent yield of copper?

6. Which method was most cost efficient?

7. Look at the waste products produced by each reaction. Which method do you think has the most significant environmental impact?

8. Based on your three answers above, which method of copper extraction is the best? Justify your answer.

9. The average grade of copper ores worldwide right now is around 1.5% CuCO₃. Using the method you selected above, how much copper could you extract from one truckload of ore? A truckload is approximately 63 tons.

(1 ton = 907,185 grams)

10. If copper sells for $10.85 per 100 grams, did either of your methods turn a profit?

Conclusion

Summary

• Restate results of lab in one succinct sentence.

Purpose Analysis

• Did you accomplish your purpose?
• Use specific data to support your conclusion

Source of Error

• Explain how the following sources of error would have impacted your results (% yield of copper).

1. The Bunsen burner flame in method one was not hot enough to completely decompose the CuCO₃.
2. In method two, some FeSO₄ stuck to the copper and was not washed away in stage two.

• Identify one additional source of error, explain its effect on your results, and how you could prevent/minimize this source of error.

Application

• Select another metal that is useful in industry, and describe (in a short paragraph) what methods are currently used to extract it from its ore.