SC4: extracting metals and equilibria

Question 1

the more reactive a metal is…

Answer 1

the more vigorous its reactions are
the more easily it loses electrons in reactions to form cations

Question 2

metal + water

Answer 2

metal hydroxide + hydrogen

Question 3

metals that react quickly with cold water are…?

Answer 3

very reactivr

Question 4

metal + steam

Answer 4

metal oxide + hydrogen

Question 5

how do metals that react slowly with cold water react with steam?

Answer 5

quickly

Question 6

what happens in the reactions of metals with water, steam and acids?

Answer 6

-the metals lose electrons and form cations
-the metal is oxidised and the water is reduced

Question 7

which metals don’t react with dilute acids?

Answer 7

metals below hydrogen in the reactivity series

Question 8

what happens in the reactions of metals with water, steam and acids?

Answer 8

-the metals lose electrons and form cations
-the metal is oxidised and the water is reduced
-hydrogen is produced

Question 9

how does reactivity affect metals tendency to form cations?

Answer 9

-the higher up a metal, the more likely to form cations
-the lower down a metal, the more likely to resist oxidation

Question 10

displacement reaction

Answer 10

a reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter’s ions

Question 11

how can the reactivity series be deduced?

Answer 11

by doing several displacement reactions; a piece of metal is dipped into a salt solution, different combinations of metal and salt solution are tested

Question 12

what does it mean if something has been coated in a displacement reaction?

Answer 12

the metal reacting with the solution has displaced it

Question 13

spectator ions

Answer 13

ions that do not participate in a reaction

Question 14

redox reaction

Answer 14

an oxidation reaction paired with a reduction reaction

Question 15

what do metals with a higher reactivity than hydrogen do in displacement reactions?

Answer 15

the displace hydrogen from acids

Question 16

ore

Answer 16

a rock that contains enough of a metal or a metal compound to make extracting the metal worthwhile

Question 17

low grade ores vs high grade ores

Answer 17

-low-grade ores = small percentage of the metal or its compound
-high-grade ores contain a larger percentage

Question 18

how are unreactive metals found?

Answer 18

they are found in the earth as the metal itself

Question 19

why isn’t electrolysis used to extract all metals?

Answer 19

large amounts of electrical energy are needed so it’s expensive

Question 20

how is a metal extracted if it’s less reactive than carbon?

Answer 20

heating with carbon

Question 21

metal oxide + carbon

Answer 21

metal + carbon dioxide

Question 22

extracting iron

Answer 22

-as iron is below carbon in the reactivity series it can be displaced from its compounds by heating with carbon
-iron is extracted from iron ore in a a blast furnace
-iron(III) oxide is reduced to molten iron when it reacts with carbon

Question 23

how are metals higher than carbon extracted?

Answer 23

electrolysis

Question 24

how is impure copper purified?

Answer 24

electrolysis

Question 25

what are electrolytes?

Answer 25

ionic compounds in the molten state or dissolved in water

Question 26

what are electrodes?

Answer 26

charged metal plates

Question 27

cathode

Answer 27

negative electrode

Question 28

anode

Answer 28

negative electrode

Question 29

what happens at the cathode & anode in electrolysis?

Answer 29

cathode: metal ions gain electrons & form an atom anode: substance loses electrons & forms a gas

Question 30

electrolysis of aluminium oxide

Answer 30

-aluminium oxide is insoluble in water, so it must be molten -the melting point of aluminium oxide is high, a lot of energy must be transferred to break its strong ionic bonds, and this is expensive -to reduce costs, powdered aluminium oxide is dissolved in molten cryolite -this ionic compound melts at a lower temperature than aluminium oxide, reducing costs -both electrodes are made of graphite -at the cathode, aluminium ions gain electrons and form aluminium atoms -at the anode, oxide ions lose electrons and form oxygen gas

Question 31

steps of recycling metals

Answer 31

1. collecting and transporting the used items to a recycling centre 2. breaking up and sorting the different metals 3. removing impurities from the metals (the metals can then be used to manufacture new metal items)

Question 32

advantages of recycling metals

Answer 32

1. more economic - less energy is needed to produce a metal 2. less damage to the environment - fewer quarries and mines, less noise and less heavy traffic 3. saves valuable raw materials - reserves of metal ores will last longer

Question 33

disadvantages of recycling

Answer 33

-the collection and transport of used items needs organisation, workers, vehicles and fuel -it can be difficult to sort different materials from one another

Question 34

simple way to separate aluminium from iron

Answer 34

a magnet or electromagnet will attract iron but not aluminium

Question 35

why is a life cycle assessment (LCA) carried out?

Answer 35

carried out to assess the environmental impact of products

Question 36

main stages of a LCA

Answer 36

1. obtaining the raw materials needed for manufacture 2. manufacturing the product 3. using the product 4. disposing of the product at the end of its useful life

Question 37

impact of raw materials (LCA)

Answer 37

-using up limited resources such as ores and crude oil -damaging habitats through quarrying, mining, or felling trees

Question 38

impact of manufacture (LCA)

Answer 38

using up land for factories the use of machines and people

Question 39

impact of use (LCA)

Answer 39

-the impact of a product on the environment during its use depends on the type of product -for example, a wooden chair has very little impact, unless it needs cleaning or repair -on the other hand, a car will have a significant impact

Question 40

impact of disposal (LCA)

Answer 40

-using up land for landfill sites -whether any or all of the product can be recycled or reused

Question 41

phytoextraction steps

Answer 41

1. plants are grown on a low-grade ore that contains lower amounts of metal 2. the plants absorb metal ions through their roots and concentrate these ions in their cells 3. the plants are harvested and burnt 4. the ash left behind contains a higher concentration of the metal than the original ore 5. the ash is processed to obtain the metal

Question 42

phytoextraction advantages & disadvantages

Answer 42

advantages -reduces the need of mining -conserves limited supplies of valuable ores disvantages -slow

Question 43

quarries

Answer 43

-large holes in the ground for mining -create noise, dust and traffic -destroy natural habitats

Question 44

biobleaching

Answer 44

-certain bacteria can break down low-grade ores to produce an acidic solution (leachate) containing metal ions -iron is used to displace copper from the leachate -because iron is cheaper than copper, it's cost effective

Question 45

biobleaching advantages and disadvantages

Answer 45

advantages: -can extract copper -doesn't need high temps -cost effective disadvantages: -produces toxic substances (eg sulfuric acid) which damage the environment

Question 46

reversible reaction

Answer 46

the products can be changed back into the reactants

Question 47

dynamic equilibrium

Answer 47

-the proportions of reactants and products stay the same -the term 'dynamic' emphasises that the forward and the backward reactions continue to occur (at the same rate)

Question 48

when can dynamic equilibrium happen?

Answer 48

in a closed system

Question 49

haber process

Answer 49

an industrial process for producing ammonia from nitrogen and hydrogen by combining them under high pressure in the presence of an iron catalyst

Question 50

haber process steps

Answer 50

1. nitrogen (extracted from the air) and hydrogen (obtained from natural gas) are pumped through pipes 2. a compressor increases the gas pressure to 200 atmospheres 3. the pressurised gases are heated to 450°C and passed through a reaction chamber containing an iron catalyst to speed up the reaction 4. the reaction mixture is cooled so that ammonia liquefies and can be removed 5. unreacted nitrogen and hydrogen are recycled

Question 51

how can an equilibrium position be changed?

Answer 51

-change temp, pressure or concentration

Question 52

changing pressure in equilibrium

Answer 52

if the pressure is increased, the equilibrium position moves in the direction of the fewest molecules of gas

Question 53

changing concentration in equilibrium

Answer 53

if the concentration of a solute (thing dissolved) is increased, the equilibrium position moves in the direction away from this solute

Question 54

changing the temperature in equilibrium

Answer 54

-in a reversible reaction, if the reaction is exothermic in one direction, it is endothermic in the other direction -if the temperature is increased, the equilibrium position moves in the direction of the endothermic process

Question 55

exothermic

Answer 55

releases energy/heat

Question 56

endothermic

Answer 56

absorbs heat/energy

Question 57

what does the temp used in a reversible reactions depend on?

Answer 57

-low enough to get an acceptable yield -high enough to do this in an acceptable time

Question 58

what does pressure used in reversible reactions depend on?

Answer 58

-low enough to keep costs down -high enough for achievable yield