Extracting metals and equilibria

Question 1

What will the most reactive metals react with?

Answer 1

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

Question 2

What will fairly reactive metals react with?

Answer 2

Fairly reactive metals react with acids: acid + metal → salt + hydrogen

Question 3

What will all metals react with?

Answer 3

● 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

Question 4

How can you deduce the relative reactivity of some metals?

Answer 4

• 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)

Question 5

How can you deduce if one metal is more reactive than another metal?

Answer 5

● 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

Question 6

Displacement reaction in terms of oxidation

Answer 6

● 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

Question 7

Displacement reaction in terms of reduction

Answer 7

● 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

Question 8

What do metal atoms form when metals react with other substances?

Answer 8

● When metals react with other substances, metal atoms form positive ions

Question 9

What is the reactivity of a metal related to?

Answer 9

● Reactivity of a metal is related to its tendency to form positive ions- more reactive metals can form positive ions more easily

Question 10

Reactivity series

Answer 10

● 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

Question 11

What can a more reactive metal do to a less reactive metal?

Answer 11

● A more reactive metal can displace a less reactive metals from a compound

Question 12

Where are most metals found?

Answer 12

● 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

Question 13

Where are unreactive metals found?

Answer 13

● 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)

Question 14

Oxidation

Answer 14

● OXidation is GAIN of OXygen

Question 15

Reduction

Answer 15

● reduction is LOSS of oxygen

Question 16

Recall that the extraction of metals involves reduction of ores

Answer 16

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

Question 17

What can be used to extract metals that are more reactive than carbon?

Answer 17

● 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)

Question 18

Why is electrolysis expensive?

Answer 18

● 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)

Question 19

● Extraction by heating with carbon (including iron):

Answer 19

● 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

Question 20

● Extraction by electrolysis (including aluminium):

Answer 20

○ 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).

Question 21

alternative biological methods of metal extraction:

bacterial extraction

Answer 21

○ Some bacteria absorb metal compounds
○ Produce solutions called leachates which contain them
○ scrap iron can used to be obtain the metal from the leachate

Question 22

alternative biological methods of metal extraction:

phytoextraction

Answer 22

○ 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

Question 23

Explain how a metals’ relative resistance to oxidation is related to its
position in the reactivity series

Answer 23

● 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)

Question 24

Advantages of recycling metals

Answer 24

● 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)

Question 25

Lifetime assessment

Answer 25

● These are carried out to assess the environmental impact of products in each of
these stages:
o Extracting and processing raw materials
o Manufacturing and packaging
o Use and operation during its lifetime
o Disposal at the end of its useful life, including transport and distribution
at each stage

Question 26

Is life time assessment purely an objective process?

Answer 26

No. Allocating numerical values to pollutant effects is less straightforward and
requires value judgements, so LTA (life time assessment) is not a purely objective
process

Question 27

Reversible reactions

Answer 27

● In some chemical reactions, the products of the reaction can react to produce
the original reactants
o These are called reversible reactions

Question 28

How can the direction of the reaction be changed?

Answer 28

The direction of the reaction can be changed by changing the conditions
aka if the forwards reaction takes place in hot conditions, lowering the
temperature can allow the reverse reaction to take place

Question 29

What is the ⇌ symbol used for?

Answer 29

the ⇌ symbol is used to show that a reaction is reversible

Question 30

Equilibrium

Answer 30

● equilibrium:
o rate of forward reaction = rate of backward reaction
o concentration of reacting substances stay the same

Question 31

Dynamic equilibrium

Answer 31

● dynamic equilibrium:
o once the forward and backward reaction reach equilibrium, they keep
going

Question 32

Formation of ammonia as a reversible reaction

Answer 32

● Used to manufacture ammonia, which is used to produce nitrogen-based fertilisers
● The raw materials for the Haber process are nitrogen and hydrogen.
● Nitrogen is obtained from the air and hydrogen may be obtained by reacting methane with steam
● The purified gases are passed over a catalyst of iron at a high temperature (about 450 °C) and a high pressure (about 200 atmospheres).
● Some of the hydrogen and nitrogen reacts to form ammonia.
● The reaction is reversible so ammonia breaks down again into nitrogen and hydrogen.
nitrogen + hydrogen ⇌ ammonia

Question 33

Conditions for haber process

Answer 33

● temperature 450 degrees C,
● pressure 200 atmospheres
● iron catalyst

Question 34

What are do the relative amounts of all the reacting substances at equilibrium depend on?

Answer 34

● The relative amounts of all the reacting substances at equilibrium depend on the conditions of the reaction.
● If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change.
o Effects of changing conditions on a system at equilibrium can be predicted using Le Chatelier’s Principle.

Question 35

● Effect of changing concentration on the position of dynamic equilibrium:

Answer 35

o If the concentration of one of the reactants or products is changed, the system is no longer at equilibrium and the concentrations of all the
substances will change until equilibrium is reached again.
o If concentration of reactants is increased: position of equilibrium shifts towards products (right) so more product is produced until equilibrium is reached again
o if concentration of products is increased: position of equilibrium shifts towards reactants (left) so more reactant is produced until equilibrium is reached again

Question 36

● Effect of changing pressure on the position of dynamic equilibrium:

Answer 36

o In gaseous reactions, an increase in pressure will favour the reaction that produces the least number of molecules as shown by the symbol equation for that reaction.

Question 37

● Effect of changing temperature on the position of dynamic equilibrium:

Answer 37

● If temperature is increased: equilibrium moves in the direction of the endothermic reaction (e.g. if forwards reaction is endothermic and temperature is increased, equilibrium shifts right to produce more product)
● If temperature is decreased: equilibrium moves in the direction of the exothermic reaction