Extracting Metals and Equilibria Flashcards
What products are formed when the most reactive metals react with water?
Metal hydroxide (forming an alkaline solution) and hydrogen gas
Describe the reaction between metals and oxygen
metal + oxygen -> metal oxide
Describe how displacement reactions can be used to determine the relative reactivity of metals
In displacement reactions, the more reactive metal gradually disappears as it forms a solution, while the less reactive metal coats the surface of the more reactive metal.
Which metal does not react with acids or oxygen?
Gold as its extremely unreactive
Explain displacement reactions as redox reactions
In displacement reactions, the more reactive metal is oxidised as it looses electrons to form a cation, while the less reactive metal is reduced as it gains electrons to form atoms.
What is the reactivity series of metals?
Potassium
Sodium
Calcium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
Describe the extraction of metals less reactive than carbon
Metals less reactive than carbon can be extracted from their oxides by reduction with carbon to remove the oxygen and obtain the pure metal.
How are unreactive metals typically found in the Earth’s crust?
Unreactive metals are found in the Earth’s crust as uncombined elements.
Why do metals require chemical reactions to extract them from their natural state?
Most metals are found as compound in ores which require chemical reactions to extract the metal.
What method is used to extract metals if they are more reactive than carbon?
Electrolysis
Why is electrolysis is considered 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).
Outline other alternative biological methods of metal extraction (2)
- 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. - 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.
Explain how a metal’s resistance to oxidation is related to its position in the reactivity series
Resistance to oxidation is the same as the 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).
Explain the advantages of recycling metals (4)
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).
What is the life time assessment for a product?
These are carried out to assess the environmental impact of products in each of these stages:
Extracting and processing raw materials.
Manufacturing and packaging.
Use and operation during its lifetime.
Disposal at the end of its useful life, including transport and distribution at each stage.
What are reversible reactions?
Reversible reactions are chemical reactions in which the products can react to produce the original reactant.
Can you provide an example of a reversible reaction?
Haber process
nitrogen + hydrogen ⇌ ammonia
What is equilibrium in a chemical reaction?
The rate of the forward reaction occurs simultaneously at the same rate of the backward reaction.
Describe dynamic equilibrium
Once the forward and backward reaction reach equilibrium, they keep going.
Describe the formation of ammonia as a reversible reaction between nitrogen (extracted from the air) and hydrogen (obtained from natural gas)
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 from natural gas or other sources.
The purified gases are passed over a catalyst of iron at a high temperature (about 450 °C) and a high pressure (about 200 atmospheres).
How does changing the concentration of reactants affect the equilibrium position?
If concentration of reactants is increased: position of equilibrium shifts towards products (right) so more product is produced until equilibrium is reached again.
What effect does increasing pressure have on a gaseous reaction?
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. This increases the yield of the reaction and equilibrium shifts right.
How does changing temperature affect the equilibrium position in an exothermic reaction?
Increasing the temperature, causes the position of equilibrium to shift to the left-endothermic reaction which lowers the yield.
