C4: Extracting Metals And Equilibria Flashcards
What are the products when a metal reacts with cold water?
Metal hydroxide and hydrogen gas.
What are the products when a metal reacts with steam?
Metal oxide and hydrogen gas.
What are the products when a metal reacts with dilute acids?
Salt and hydrogen.
If a metal reacts with cold water, what does it suggest about the reactivity of this metals?
It suggests the metal is very reactive as only the most reactive metals can react with cold water.
A metal reacts with oxygen but not acid or cold water. What does this suggest about the reactivity of this metal?
Not very reactive, most metals react with oxygen.
Name a metal which will not react with water, acid or oxygen?
Gold
Describe an experiment that uses displacement to compare the reactivity of two metals?
Add a solid metal to a salt solution (the salt must contain a different metal).
If the solid metal is more reactive, it will gradually disappear, displacing the metal that was in the salt solution.
If nothing happens, the metal in the salt is more reactive and can’t be displaced.
What would you expect to observe when magnesium is added to copper sulfate solution?
The copper sulfate solution is blue.
Magnesium is more reactive than copper so when magnesium is added the blue solution decolourises and copper coats the surface of the magnesium.
Why can a displacement reaction be called a redox reaction? Explain in terms of electron transfer?
A redox reaction occurs when reduction and oxidation are taking place in the same reaction.
In a displacement reaction, the more reactive metal atoms lose electrons to form ions (oxidation) and the less reactive metal ions gain electrons to form the element (reduction).
Which metals are most easily oxidised?
The metals highest in the reactivity series. More reactive metals are more likely to react with water and dilute acids to form cations.
Where are most metals extracted from?
From ores found in the Earth’s crust.
What is an ore?
A rock which contains metals often chemically combined with other substances.
Which metals are found in the earth’s crust as uncombined elements?
Unreactive metals
Explain what oxidation means in terms of oxygen?
Gain of oxygen
Explain what reduction means in terms of oxygen?
Loss of oxygen
Most ores contain metals chemically combined with oxygen. What process must be carried out to extract the metal?
Reduction
How can metals be extracted from their ores?
Reduction with carbon: Can only be done if the metal is less reactive than carbon (links to reactivity series).
Electrolysis: Can be done with all metals, but requires a large amount of energy (high cost).
How would you extract iron from its ore?
Iron is less reactive than carbon so can be extracted by reduction with carbon.
Electrolysis could also be used, but this would use a lot of unnecessary energy (high cost).
How can aluminium be extracted from its ore?
Aluminium is more reactive than carbon so electrolysis must be used.
When the molten ore undergoes electrolysis, the metal forms at the cathode.
When aluminium is extracted from aluminium oxide, why is it first dissolved in molten cryolite?
Aluminium oxide has a very high melting point. It is dissolved in molten cryolite to produce an electrolyte with a lower melting point, reducing energy usage and cost.
How can plants be used as an alternative metal extraction method? How does it work?
Phytoextraction:
Plants are grown in areas with metals in the soil. The plants take up metals through their roots and concentrate them in their shoots and leaves. These plants are burned and the metals are removed from the ash
How can bacteria be used as an alternative metal extraction method? How does it work?
Bacterial extraction:
Some bacteria absorb metal compounds. These bacteria produce solutions called leachates containing the metals. Scrap iron can be used to remove the metal from the leachate.
What are the limitations of biological methods of extraction?
- Only suitable for low grade ores with smaller quantities of metals.
- Slow processes.
- Require displacement or electrolysis for the final step.
How is a metal’s relative resistance to oxidation related to its position in the reactivity series?
Oxidation is the loss of electrons. Metals lower in the reactivity series are less reactive. This means they are less likely to form their cations so are more resistant to oxidation.
