Electrolysis, metals and equilibrium 2

Question 1

Reactivity series

Answer 1

Potassium   K.     Most reactive
Sodium.    Na
Calcium    Ca
Magnesium   Mg
Aluminium Al
Carbon.  C
Zinc.  Zn
Iron.  Fe
Hydrogen   H
Copper.   Cu
Silver.  Ag
Gold    Au.           Least reactive 
Please stop calling me a careless zebra instead try learning how copper saves gold.

Question 2

Oil Rig

Answer 2

Oxidation is loss (of electrons and gain of oxygen) Reduction is Gain (of electrons and loss of oxygen).

Question 3

Experiment to show that some metals are more reactive than others.

Answer 3

Place little pieces of metals into dilute hydrochloric acid. Show that hydrogen is forming using the burning splint. Louder the pop, more hydrogen made - more reactive.

Magnesium- loud squeaky pop, fizz vigorously.
Aluminium- fair squeaky pop
Zinc- quiet squeaky pop. Bubble a bit.
Iron- very quiet squeaky pop
Copper- no squeaky pop, not react.

The faster the bubbles form, faster the reaction and more reactive the metal.

Question 4

Metal+ water

Answer 4

Metal + water = metal hydroxide + hydrogen
Very reactive metals will react vigorously with water.
Less reactive metals won’t react with cold water but will react with steam.
Copper won’t react with either.

Question 5

Displacement reactions.

Answer 5

Example of Redox reactions where more reactive element reacts to take the place of a less reactive element in a compound.
With metal, more reactive metal loses electrons (oxidised) and less reactive metal gains electrons. (Reduced)

Question 6

Put iron nail in a solution of copper sulphate.

Answer 6

Iron (more reactive) will kick out copper (less reactive) from the salt.
Iron sulphate solution + copper metal.

Question 7

Put silver metal into solution of copper sulphate.

Answer 7

Nothing will happen. Copper is more reactive than silver.

Question 8

Ore

Answer 8

Metal ore- a rock which contains enough metal to extract. Ore is an oxide of the metal.
E.g. main aluminium ore is bauxite- aluminium oxide.
Found in earths crust
Unreactive metals are found in earths crust as uncombined elements.

Question 9

Metals extracted

Answer 9

Metals higher than carbon in reactivity series have to be extracted by electrolysis of molten compounds- expensive.
Metals below carbon are extracted by reduction using carbon.

Question 10

Extracting metals with electrolysis- what goes to the anode and cathode?

Answer 10

Metal ore is melted (electric current passed through).
Metal discharged at cathode
Non-metal at anode.

E.g. Aluminium extracted using electrolysis with carbon electrodes. Aluminium oxide dissolved in molten cryolite (aluminium compound with lower melting point than aluminium oxide).
Aluminium- cathode
Oxygen- anode
2Al2O3=4Al + 3O2

Question 11

Prices of extraction with electrolysis and reduction with carbon.

Answer 11

Reduction with carbon is cheaper.
Electricity is expensive +costs to melt a metal ore.
Lower down the reactivity series, cheaper to extract.

Question 12

Bioleaching + phytoextraction

Answer 12

Bioleaching- uses bacteria to separate metals from their ores.

phytoextraction- Plants grown in soil that contains metal compounds. Metals build up in leaves+ are burned. Ash contains metal compounds.

Question 13

Recycling materials

Answer 13

Saves energy
Infinite amount of raw materials (renewable unlike fossil fuels).
Cuts down on rubbish sent to landfill ( pollutes surroundings).
Creates jobs
Beneficial to economy to recycle metals that are expensive to extract or buy.
For every 1kg of aluminium recycled you save:
95% of emery needed to mine fresh aluminium.
4kg of aluminium ore
Lots of waste.

Question 14

Life cycle assessment + environmental impact.

Answer 14

Choice of material: metals mined and extracted - need energy+ cause pollution.
Raw material comes from crude oil (non renewable)
Manufacture: uses energy. Cause pollution- CO or HCL). Waste product disposal- some can be turned into useful chemicals reducing pollution. Make sure businesses don’t put polluted water back in environment.
Product use: paint - toxic fumes
Burning fuels- greenhouse gases + harmful substances.
Fertilisers- leach into streams + damage ecosystem.
Disposal: landfill site- takes up space + pollute land and water.
Incineration- causes air pollution.

Question 15

Reversible reactions

Answer 15

Products can react to produce original reactants.

Question 16

Haber process

Answer 16

Example of reversible reaction.
Nitrogen + hydrogen = ammonia N2 + 3H2 = 2NH3.
Nitrogen: obtained from air (78% nitrogen)
Hydrogen: extracted from hydrocarbons from sources e.g. natural gas + crude oil.
Carried out at 450 degrees with pressure of 200 atmospheres and an iron catalyst.

Question 17

Equilibrium

Answer 17

When the forward reaction is going at the same rate as the backward reaction.
Both reactions are happening but there’s no overall effect.
Can only happen in closed system so no reactants or products can escape.
Sometimes the equilibrium will lie to the left (lots of reactants but not much products) or right (lots of products but not much reactants).

Question 18

Dynamic equilibrium

Answer 18

Forward and backward reactions happening at the same time and same rate, and concentrations of reactants and products have reached a balance and won’t change.

Question 19

What can change the position of the equilibrium?

Answer 19

Temperature, pressure (involving gas), concentrations (of reactants or products).

Question 20

Le Chatelier’s principle

Answer 20

If there’s a change in concentration, pressure or temperature in a reversible reaction, the equilibrium position will move to help counteract that change.

Question 21

Temperature

Answer 21

Decrease temp- equilibrium will move in exothermic (releases energy) direction to produce more heat.
Increase temp- equilibrium will move in endothermic (absorb energy) direction to absorb extra heat.

Question 22

Pressure

Answer 22

Only effects equilibria involving gases

Increase pressure- equilibrium will move towards side that has fewer moles of gas to reduce pressure.
Decrease pressure- equilibrium will move towards side that has more moles of gas to increase pressure.

Question 23

Concentration

Answer 23

Increase concentration of reactants, equilibrium will move to the right to use up the reactants (making more products).
Increase concentration of products, equilibrium will move to the left to use up the products ( making more reactants).
Decreasing concentration will have opposite effect.

Question 24

How can you increase yield? (How much product you get)

Answer 24

Changing the conditions to shift the equilibrium position to the right (towards the products).

Question 25

Advantages and disadvantages of bioleaching and phytoextraction

Answer 25

Advantages- no harmful gases
Causes less damage to the landscape than mining
Conserves supplies of higher grade ores

Disadvantage- very slow

Question 26

Advantages and disadvantages of bioleaching

Answer 26

Advantage- doesn’t require high temperatures

Disadvantage- toxic substances and sulphuric acid can be produced and damage the environment

Question 27

Advantages and disadvantages of phytoextraction

Answer 27

Advantage- Can extract metals from contaminated soils
Disadvantage- more expensive than mining some ores
Growing plants is dependant on weather conditions

Question 28

What happens to negative ions at the anode

Answer 28

They lose electrons and are oxidised

Question 29

What happens to the positive ions at the cathode

Answer 29

Electrons are transferred from the cathode to the positive ions and are reduced

Question 30

In the electrolysis of copper sulphate solution, what happens to the anode and cathode

Answer 30

Mass of anode decreases

Mass of cathode decreases

Question 31

Disadvantage of extracting nickel from its ore rather than by phytoextraction

Answer 31

Mining is bad for the environment because it causes habitat loss