Extracting metals and equilibria Flashcards
(37 cards)
What will the most reactive metals react with?
The most reactive metals will react with cold water:
○ Products are a metal hydroxide (forming an alkaline solution) and
hydrogen gas
○ E.g. with potassium: 2K + 2H2O -> 2KOH + H2
What will fairly reactive metals react with?
Fairly reactive metals react with acids: acid + metal → salt + hydrogen
What will all metals react with?
● Almost all metals react with oxygen: metal + oxygen -> metal oxide, though more
reactive metals will react with oxygen more quickly
● Only metal that does not react with any of the above is gold, because it is extremely unreactive
How can you deduce the relative reactivity of some metals?
- You can therefore deduce the relative reactivity of some metals by seeing if they react with water (i.e. VERY reactive), acid (reactive), and oxygen (not that reactive).
- For these reactions, you can see if they have taken place by looking for bubbles (if hydrogen is produced)
How can you deduce if one metal is more reactive than another metal?
● You can see if one metal is more reactive than another by using displacement
reactions…
○ Easily seen when a salt of the less reactive metal is in the solution
■ More reactive metal gradually disappears as it forms a solution
■ Less reactive metal coats the surface of the more reactive metal
Displacement reaction in terms of oxidation
● More reactive metals form a cation (+) as they displace the less reactive metal,
losing electrons and therefore being OXIDISED (Oxidation Is Loss of electrons), it
forms an ion as it replaces the less reactive metal in the salt solution
Displacement reaction in terms of reduction
● Less reactive metals form atoms from negative ions as they are displaced,
gaining electrons and therefore being REDUCED (Reduction Is Gain of electrons),
it forms an atom as it is replaced in the salt solution
What do metal atoms form when metals react with other substances?
● When metals react with other substances, metal atoms form positive ions
What is the reactivity of a metal related to?
● Reactivity of a metal is related to its tendency to form positive ions- more reactive metals can form positive ions more easily
Reactivity series
● Metals can be arranged in order of their reactivity in a reactivity series
o Metals potassium, sodium, lithium, calcium, magnesium, zinc, iron and copper can be put in order of their reactivity from their reactions with water and dilute acids
o Non-metals hydrogen and carbon are often included in the reactivity series
What can a more reactive metal do to a less reactive metal?
● A more reactive metal can displace a less reactive metals from a compound
Where are most metals found?
● Most metals are extracted from ores found in the Earth’s
crust
● But, most metals are found as compounds that require chemical reactions to extract the metal, since they have reacted with other compounds/elements
Where are unreactive metals found?
● Unreactive metals are found in the Earth’s crust as the
uncombined elements
● You will notice that the last element is gold, since it is very unreactive, it is found in the Earth as the metal itself (unreacted with anything)
Oxidation
● OXidation is GAIN of OXygen
Reduction
● reduction is LOSS of oxygen
Recall that the extraction of metals involves reduction of ores
Metals less reactive than carbon:
○ Can be extracted from their oxides by reduction with carbon
■ Don’t forget: reduction involves the loss of oxygen, so you are
reducing the ores to remove the oxygen to obtain the pure metal
What can be used to extract metals that are more reactive than carbon?
● Can only be extracted by reduction of carbon if metal is less reactive so that carbon displaces the metal from the ore…
● If more reactive than carbon, electrolysis can be used (metals less reactive than carbon can also be extracted this way)
Why is electrolysis expensive?
● Electrolysis is expensive due to the use of large amounts of energy to melt the compounds and to produce the electrical current (so you wouldn’t extract a metal using electrolysis if it could be done more cheaply using carbon)
● Extraction by heating with carbon (including iron):
● Extraction by heating with carbon (including iron):
○ Iron oxide loses oxygen, and is therefore reduced. The carbon gains
oxygen, and is therefore oxidised.
○ 2Fe2O3(s) + 3C(s) -> 4Fe(l) + 3CO2(g)
○ For iron, this is carried out at high temperatures in a blast furnace
● Extraction by electrolysis (including aluminium):
○ Metals that are more reactive than carbon e.g aluminium are extracted
by electrolysis of molten compounds.
■ Too reactive to be extracted by reduction with carbon
■ Aluminium is manufactured by the electrolysis of a molten
mixture of aluminium oxide and cryolite using carbon as the
positive electrode (anode).
alternative biological methods of metal extraction:
bacterial extraction
○ Some bacteria absorb metal compounds
○ Produce solutions called leachates which contain them
○ scrap iron can used to be obtain the metal from the leachate
alternative biological methods of metal extraction:
phytoextraction
○ Some plants absorb metal compounds through their roots
○ They concentrate these compounds into their shoots and leaves
○ The plants can be burned to produce an ash that contains the metal
compounds
Explain how a metals’ relative resistance to oxidation is related to its
position in the reactivity series
● Relative resistance to oxidation is the same as relative resistance to losing electrons / forming positive metal ions
○ less reactive a metal is, the more resistant it is to oxidation, because for a metal to react, it forms a positive metal ion by losing electrons (loss of electrons=oxidation)
Advantages of recycling metals
● Recycling is important to achieve sustainable development
○ Requires less energy to melt and remould metals than it does to extract new metals from their ores
○ Mining ores is bad for the environment as large quarries are created, which produce noise pollution and dust
○ Also, recycling allows for waste metals to be reused, saving money, helping the environment and the supply of valuable raw materials
(meaning metal ores will last longer)
