CHEMISTRY · Stage 9 · Chapter 12: Chemical Reactions 3 and Rates
Chemistry 12.5 Extracting copper — Malachite Decomposition and Displacement
5 min read 6 parts Lesson 5 of 13
Lesson summary
12.5 Extracting copper — Malachite Decomposition and Displacement — Alhussan International Academy — Chemistry (Stages 7–9) notes: Describe how copper is obtained from malachite and from waste, and the environmental impacts of copper mining and extraction.Uses — copper makes wate…
- Reactivity
- Observations
- Reduction with carbon
- Idea behind both routes
- Percentage yield
- Improvements
Part 1 of 6Copper and malachite
- Usescopper makes water pipes, electric wires, electrical wiring, heat exchangers and coins.
- Malachitea green ore containing copper carbonate.
- Reactivitycopper is low in the reactivity series, so it can be obtained from its compounds fairly easily.
Part 2 of 6Stage 1: thermal decomposition
- Method — heat powdered malachite strongly in a boiling tube fitted with a delivery tube leading to limewater.
- Observations — the green powder turns black and the limewater goes cloudy.
- Equation — copper carbonate → copper oxide + carbon dioxide.
- The black solid is copper oxide, and the cloudy limewater shows carbon dioxide was released.
- The mass of solid decreases as the gas escapes.
Part 3 of 6Stage 2: getting the copper
1Reduction with carbon1 point
— mix copper oxide with carbon powder and heat strongly in a crucible.
- copper oxide + carbon → copper + carbon dioxide, and pink-brown copper is seen.
2Displacement2 points
— add the copper oxide to warm dilute sulfuric acid to make blue copper sulfate solution.
- copper oxide + sulfuric acid → copper sulfate + water.
- Then add a more reactive metal such as iron or zinc: iron + copper sulfate → iron sulfate + copper.
3Idea behind both routes
— copper is a low-reactivity metal, so a more reactive substance can remove its oxygen or take its place.
| Route | Advantages | Disadvantages |
|---|---|---|
| Heating with carbon | Few steps | Needs high temperature, makes carbon dioxide |
| Displacement | Lower temperature | Uses acid, produces waste solution |
Part 4 of 6Safety and evaluation
1Safety2 points
— wear eye protection, hold the boiling tube at an angle pointing away from people and heat gently at first to avoid spitting.
- Remove the delivery tube from the limewater before stopping heating to prevent suck-back, which could crack the tube.
- Dilute sulfuric acid is an irritant, and copper compounds are harmful if swallowed.
2Percentage yield1 point
= actual mass ÷ expected mass × 100.
- Yields are below 100% because some oxide does not react, some is lost in transfer or filtering, and copper may re-oxidise on heating in air.
3Improvements
— grind the reactants finely, heat in a closed tube and use a little excess carbon.
Part 5 of 6Environmental impacts of copper mining
- Waste rockhuge piles of waste rock cover land that cannot be used for farming or houses, and few plants and animals survive.
- Pollutionnoisy lorries and machinery pollute the air, and acidic water must be managed so rivers are not polluted.
- Energy and gasesmining and extraction need huge amounts of energy and make large amounts of greenhouse gases such as carbon dioxide, which cause climate change.
- Increasing demandsolar cells and wind turbines are connected by copper cables, so more renewable electricity increases world demand for copper.
Part 6 of 6Better ways of extracting copper
1Advantages
— compared with mined ore, these methods are less harmful to the environment, need less energy and cost less.
2Recycling2 points
— companies collect used copper objects such as water pipes and computer parts and heat them to 1085 °C.
- The copper melts and is poured into moulds, where it freezes as ingots that are sold and made into new objects.
- This method has been used for hundreds of years.
3Extracting from waste2 points
— some devices and mine waste contain very small amounts of copper.
- Spray sulfuric acid onto the waste to make copper sulfate solution.
- Add waste iron, which is higher in the reactivity series, to displace copper: iron + copper sulfate → iron sulfate + copper.
4Phytomining1 point
— some plants grow well on soil mixed with copper ore waste, and copper ions enter through the roots and are stored in their cells.
- The crop is harvested and burned, and the ash is rich in copper compounds.
5Bioleaching
— bacteria are used to extract copper from low-grade ore.
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