Topic 4- extracting metals and equilibria (with spec) paper 1

Question 1

What is oxidation?

Answer 1

the gain of oxygen

Question 2

What is reduction?

Answer 2

the removal of oxygen

Question 3

What is combustion?

Answer 3

it involves oxidation. they’re always exothermic.

Question 4

recall the reactivity series

Answer 4

Potassium
Sodium
Calcium
Magnesium
Aluminium
(Carbon)
Zinc
Iron
(Hydrogen) 
Copper 
Silver 
Gold 

The metals at the top are the most reactive, they easily lose their electrons to form cations (positive ions)

Question 5

How can you determine a metal’s position in the reactivity series?

Answer 5

reacting it with water and dilute acids

Question 6

how can you find the reactivity of a metal with an acid?

Answer 6

place the metal in hydrochloric acid and see how much it reacts. the more reactive metals will fizz more vigorously but less reactive metals with only bubble a little bit

Question 7

how can you find the reactivity of a metal with water?

Answer 7

very reactive metals like potassium and sodium will all react vigorously with water but less reactive metals won’t react much. copper won’t react with water. in potassium the potassium catches on fire.

e.g. sodium + water = sodium hydroxide + hydrogen

Question 8

what is another word for displacement reactions?

Answer 8

redox reactions. they are either oxidised or reduced which can also be known as a gain or loss in electrons.

Question 9

how can you find the reactivity of a metal with a salt solution?

Answer 9

if you put a reactive metal into a solution of less reactive metal salt, the reactive metal will replace the less reactive metal in the salt. if you put a less reactive metal into a solution of a more reactive metal salt, nothing will happen

Question 10

where are most of metals extracted from?

Answer 10

from ores found in the earth’s crust where the metals are then extracted

Question 11

where are unreactive metals found?

Answer 11

in the earth’s crust as uncombined elements, these are mined straight out of the ground but often need to be refined before they can be used

Question 12

what does the extraction of metals involve?

Answer 12

A metal can be extracted from its ore chemically by reduction using carbon. When an ore is reduced, oxygen is removed from it. Eg. Iron oxide + carbon = iron + carbon dioxide

the position of the metal on the reactivity series determines whether it can be reduced by carbon

Question 13

what is a metal ore?

Answer 13

a rock that contains enough metal to make it economically worthwhile extracting the metal from it.

Question 14

which metals are extracted by reduction using carbon?

Answer 14

metals below carbon. this is because carbon can only take the oxygen away from metals which are less reactive Ethan itself.

zinc, iron, tin, copper, silver, gold

Question 15

which metals are extracted by the use of electrolysis

Answer 15

metals above carbon (metals more reactive than carbon). this is more expensive.

potassium, sodium, calcium, magnesium, aluminium

Question 16

how does electrolysis work for the extraction of metals above carbon?

Answer 16

they are extracted using molten compounds.
once the metal ore is melted, an electric current is passed through it. the metal is discharged at the cathode and the non- metal at the anode

Question 17

why is electrolysis more expensive than reduction with carbon?

Answer 17

• demands for a large amount of electricity which is pricey
• carbon is cheap and acts as a fuel to provide the heat needed for the reaction reaction to happen
• it is cheaper to extract the less reactive metals than the more reactive metals at the top of the reactivity series

Question 18

What are the biological methods in extracting metals?

Answer 18

bioleaching and photoextraction

Question 19

what is happening because of the increased demand for metals?

Answer 19

it may lead to shortages in the future. scientists are looking into extracting metals from low-grad metals (ores that only contain a small amount of metals) or from the waste that is currently produced when the metals are extracted.

Question 20

what is bioleaching?

Answer 20

This uses bacteria to separate metals from their ores. The bacteria get energy from the bonds between the atoms in the ore, separating the metal form the ore in the process. The leachate (solution produced by the process) contains metal ions, which can be extracted by electrolysis or displacement with a more reactive metal.

Question 21

what is phytoextraction?

Answer 21

This involves growing plants in soil that contains metal compounds. The plants can use or get rid of the metals sp they gradually build up in the leaves. The plants can be harvested, dried or burned in a furnace and ashes can be picked up, which’ll contain the metal compound which can then be extracted by electrolysis or displacement reactions.

Question 22

what are the pros and cons of using phytoextraction and bioleaching for extracting metals?

Answer 22

pros: much smaller impact to the environment
cons: slow

Question 23

what determines a metal’s relative resistance to oxidation?

Answer 23

its position on the periodic table

Question 24

what are three advantages of recycling metals?

Answer 24

• it conserves resources and energy, there are a finite amount of fossil fuels and recycling saves energy as not much energy is needed
• it protects the environment as it reduces the risk of rubbish going to a landfill which pollutes the surroundings
• recycling metals that are expensive to extract or buy is very beneficial to the economy and it creates jobs in the different areas and steps of recycling

Question 25

what is a life cycle assessment?

Answer 25

it has to be carried out when a company wants to manufacture a product and involves consideration of the effect on the environment of:

1) obtaining the raw materials (use of non-renewables)
2) manufacturing the product (cause a lot of pollution)
3) product use (fertilisers damage ecosystems)
4) disposing of the product (may be burnt which leads to pollution)

Question 26

what are chemical reactions also?

Answer 26

they are reversible. the is where the products can react with each other to produce the original reactants. the direction of some reversible reactions can be altered by changing the reaction conditions

Question 27

what is an example of a reversible reaction?

Answer 27

the haber process

during the formation of ammonia from nitrogen (which is obtained from the air) and hydrogen (obtained from natural gas) it can reach dynamic equilibrium

Question 28

what is meant by dynamic equilibrium?

Answer 28

in a reversible reaction when the forward and backward reactions are both happening at the same time and at the same rate, and the concentrations of reactants and products have reached a balance and can’t change

Question 29

when can equilibrium only be achieved?

Answer 29

in a closed system. this is when none of the reactants or products can escape

Question 30

what are the conditions for the haber process?

Answer 30

• temperature at 450ºc
• pressure of 200 atmospheres
• use of an iron catalyst

Question 31

what are the 3 changes that affect the position of a dynamic equilibrium?

Answer 31

• temperature
• pressure
• concentration

Question 32

what was Le Chatelier’s principle?

Answer 32

he sates that if there is a change in temperature, concentration or pressure in a reversible reaction, the equilibrium position will move to help counteract that change

Question 33

explain a change in temperature using le chatelier’s principle

Answer 33

all reactions are exothermic in one direction and endothermic in the other

• if you decrease the temperature, the equilibrium will move in the exothermic direction to produce more heat
• if you increase the temperature, the equilibrium will move in the endothermic direction to absorb the extra heat

Question 34

explain a change in pressure using le chatelier’s principle

Answer 34

changing this only effects equilibria involving gases

• increasing the pressure means that the equilibrium will move towards the side where there are fewer moles of gas to reduct the pressure
• decreasing the pressure means that the equilibrium will move towards where there are more moles of gas to increase pressure

Question 35

explain a change in concentration using le chatelier’s principle

Answer 35

• if you increase the concentration of the REACTANTS, the equilibrium will move to the right to use up the reactants (make more products)
• if you increase the concentration of the PRODUCTS, the equilibrium will move to the left to use up the products (make more reactants)
• decreasing the concentration will have the opposite effect

Question 36

Why in the extraction of metal is cryolite often used?

Answer 36

To lower the boiling point of the electrolyte/ore