Obtaining and using metals 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
Write the chemical equation for the reaction that
occurs when calcium reacts with cold water
Ca + 2H2O → Ca(OH)2
+ H2
(Check google if unsure)
Write the chemical equation for the reaction that
occurs when zinc reacts with steam
Zn + H2O → ZnO +H2
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)
‘Fill in the gap: ‘The reactivity of a metal is related to
its tendency to form _______ ’
Cations (positive ions)
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).
What is the chemical equation for the reduction of
iron with carbon?
2Fe2O3 + 3C → 4Fe + 3CO2
Check google if unsure
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.
What are the advantages of recycling metals?
- Economically beneficial because electrolysis is expensive.
- Prevents the detrimental environmental impact of mining and
extraction of new metals. - Less waste produced so less landfill.
- Less energy required compared to electrolysis.
- More sustainable - not using up the finite resources.
- Recycling process provides employment.
What is a life cycle assessment?
Analysis of the overall environmental
impact that a product may have
throughout its lifetime.
What different factors does a life cycle assessment
of a product consider?
- Extraction and processing of raw materials.
- Manufacturing.
- Packaging and transportation.
- Use of the product.
- Disposal.
