Extracting Metals and Equilibria

Question 1

What does oxidisation mean?

Answer 1

can mean the reaction with/addition of oxygen e.g. CO is oxidised to CO2

Question 2

What does reduction mean?

Answer 2

Can mean the reduction of oxygen

Question 3

What does OILRIG stand for?

Answer 3

Oxidation Is Loss (of electrons)

Reduction Is Gain (of electrons)

Question 4

What do combustion reactions involve?

Answer 4

Oxidation - they are always exothermic

Question 5

What does the reactivity series show?

Answer 5

Lists metals in order of reactivity - shows how easily they are oxidised

Question 6

What do positions on the reactivity series compared to carbon show?

Answer 6

a metal’s position compared to carbon dictates how it is extracted from its ore

Question 7

What do positions on the reactivity series compared to hydrogen show?

Answer 7

a metal’s position compared to hydrogen shows how it reacts with dilute acids

Question 8

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

Answer 8

by reacting the metal with water and dilute acids

Question 9

What is an experiment you can do to measure the reactivity of metals?

Answer 9

dropping pieces of metal into dilute hydrochloric acid - v reactive metals (e.g. magnesium) fizz vigorously where as less reactive metals (e.g. zinc) only bubble - copper won’t react at all

Question 10

How can you show if hydrogen is forming when testing for reactivity?

Answer 10

using the burning splint test - the louder the pop the more hydrogen present and so the more reactive the metal is

Question 11

What is the equation for metals reacting with water?

Answer 11

metal + water -> metal hydroxide + hydrogen

Question 12

How do different metals react with water?

Answer 12

reactive metals e.g. potassium, sodium, lithium and calcium react vigorously,
less reactive metals e.g. magnesium, zinc and iron don’t react much but will react with steam
copper wont react

Question 13

What are displacement reactions an example of?

Answer 13

redox reactions - a more reactive element is oxidised and takes the place of a less reactive element which is reduced

Question 14

How do displacement reactions work?

Answer 14

if you put a more reactive metal into a solution containing a less reactive salt - the more reactive metal will replace the less reactive metal in the salt e.g. magnesium + copper nitrate -> magnesium nitrate + copper

Question 15

What is the order of reactivity for the metals used in displacement?

Answer 15

1. magnesium
2. zinc
3. copper

Question 16

What is a metal ore?

Answer 16

a rock which contains enough metal to make it economically worthwhile to extract the metal from it - ores are often oxides of metals

Question 17

What is aluminium ore called?

Answer 17

bauxite - also known as aluminium oxide

Question 18

How is carbon used to extract metals from its ore?

Answer 18

carbon can take oxygen away from metals which are less reactive than carbon itself - so metals that are less reactive than carbon can be extracted by reduction using carbon e.g. iron oxide is reduced in a blast furnace to make iron (anything more reactive than carbon must be extracted using electrolysis though)

Question 19

What are the different ways metal can be extracted from its ore?

Answer 19

1. electrolysis

2. reduction using carbon

Question 20

How is electrolysis used to extract metals from its ore?

Answer 20

melt the metal ore so that an electric current can pass through - the metal is discharged at the cathode and the non-metal at the anode

Question 21

What are the downsides of using electrolysis to extract metals from ores?

Answer 21

it is expensive - a large amount of electricity is needed along with the costs associated with melting/dissolving the ore - reduction using carbon is much cheaper and the carbon acts as a fuel to provide heat needed for the reduction reaction to happen - this means that the less reactive metals are cheaper to extract than more reactive metals

Question 22

What are the biological methods that can be used to extract metals from their ores?

Answer 22

1. bleaching
2. photoextraction
   - better for the environment but a slow process

Question 23

How does bioleaching work to extract metals?

Answer 23

1. bacteria gets energy from the bonds between the atoms in the ore
2. this causes the metal to separate out
3. a leachate (solution) is produced which contains metal ions - this can then be extracted e.g. by electrolysis/displacement with more reactive metal

Question 24

How does photoextraction work to extract metals?

Answer 24

1. plants are grown in soil containing metal compounds
2. the plants can’t use or get rid of the metals so they build up in the leaves
3. the plant is then harvested, dried and burned in a furnace
4. the ash from this contains the metal compounds which can then be extracted by electrolysis or displacement reactions

Question 25

Why is recycling good?

Answer 25

1. conserves resources and energy (extracting new materials uses fossil fuels and expensive extraction methods) 2. protects the environment (mines are damaging to environment, landfill is polluting) 3. economic benefits (saves money from extraction methods, creates jobs, recycling expensive metals is Good)

Question 26

Why is recycling aluminium good?

Answer 26

- 4 tonnes of ore needed for 1 tonne of aluminium - mining aluminium messes up landscape (esp. rainforests) and transportation and extraction is expensive - for every 1kg of aluminium cans recycled you save 95% of energy needed to extract new aluminium and 4kg of aluminium ore

Question 27

What is a life cycle assessment?

Answer 27

an assessment of each stage if the life of a product - working out the potential environmental impact of each stage

Question 28

What are the factors that are considered in a life cycle assessment?

Answer 28

1. choice of material 2. manufacture 3. product use 4. disposal

Question 29

How is the choice of metal assessed in a life cycle assessment?

Answer 29

1. metals must be mined and extracted from their ore - using energy and causing pollution 2. raw materials often come from crude oil - non-renewable with decreasing supplies refining into useful raw materials requires energy and causes pollution

Question 30

How is the manufacture assessed in a life cycle assessment?

Answer 30

1. manufacturing uses lots of energy and other resources 2. causes pollution and harmful fumes e.g. CO 3. waste products considered - some can be recycled and turned into other useful chemicals - reducing amount that ends up in environment 4. most chemical manufacture uses water - businesses must make sure they don't put polluted water back into the environment

Question 31

How is the product use assessed in a life cycle assessment?

Answer 31

1. using product may damage the environment e.g. paint gives off toxic fumes, burning fuels releases greenhouse gases and fertilisers leach into streams

Question 32

How is the disposal assessed in a life cycle assessment?

Answer 32

1. products often disposed of in a landfill site - takes up space and pollutes land 2. products might be incinerated - causing air pollution

Question 33

What is a reversible reaction?

Answer 33

a reaction where the products of the reaction can react with each other to produce the original reactants - A + B ⇌ C + D

Question 34

What is an example of a reversible reaction?

Answer 34

the Haber process - nitrogen and hydrogen react to form ammonia - nitrogen is obtained from the air and hydrogen is extracted from hydrocarbons from sources e.g. crude oil - the Haber process is carried out at 450ºC with a pressure of 200 atmospheres and an iron catalyst

Question 35

How do reversible reactions reach equilibrium?

Answer 35

1. the reactants react and their concentrations fall so the reaction slows down 2. as product concentration increases the backward reaction speeds up 3. after a while the forward and backward reactions will go at the same rate - equilibrium is reached and there will be no overall effect - this doesn't always mean the products and reactants are completely equal and it usually depends on the conditions as to where it lies - equilibrium can only happen in a closed system

Question 36

What does dynamic equilibrium mean?

Answer 36

in reversible reactions - the forward and backward reactions happen at the same time and same rate, the concentrations have reached a balance and will not change

Question 37

What are the three things that can change the position of equilibrium?

Answer 37

1. temperature 2. pressure (in gases) 3. concentration e. g. ammonium chloride ⇌ ammonia + hydrogen chloride: heating this reaction moves the equilibrium to the right and cooling it moves it to the left

Question 38

What does Le Chatelier's Principle state?

Answer 38

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

Question 39

How does temperature cause a change in the position of equilibrium?

Answer 39

all reactions are exothermic in one direction and endothermic in the other - so if you decrease the temperature the equilibrium will move in the exothermic direction to produce more heat - if you increase the temperature equilibrium will move in the endothermic direction to absorb the extra heat

Question 40

How does pressure cause a change in the position of equilibrium?

Answer 40

increasing the pressure means equilibrium will move towards the side with fewer moles of gas to reduce pressure (vice versa)

Question 41

How does concentration cause a change in the position of equilibrium?

Answer 41

increasing the concentration of reactants means equilibrium will move to the right in order to use up the reactants (making more products) - increasing product concentration means equilibrium will move to the left to use up the products (decreasing concentration has opposite effect)

Question 42

Do you know how to predict how the position of equilibrium will change?

Answer 42

according to Le Chatelier's Principle (pg 122)