Chemistry C4-6

The electrolysis of aluminium is made of the electrolyte: Al2O3, aluminium oxide (bauxite) and it is molten with cryolite, because it lowers the melting point. It has to be molten in order for the ions to move.

Anode is positive and cathode is negative (PANIC)

Anode: Al 3+ +3e- -> Al (l)

Cathode: 2O 2- (l) -> O2(g) + 4e-

They are both made from carbon - the anode is made of graphite and the cathode is carbon.

Aluminium forms positive ions so is attracted to the cathode, this surrounds the electrolyte so the aluminium forms at the bottom of the case.

The oxygen forms negative ions so is attracted to the anode, because of this carbon dioxide forms at the anode and it has to be replaced often.

They are both made from carbon - the anode is made of graphite and the cathode is carbon.

Aluminium forms positive ions so is attracted to the cathode, this surrounds the electrolyte so the aluminium forms at the bottom of the case.

The oxygen forms negative ions so is attracted to the anode, because of this carbon dioxide forms at the anode and it has to be replaced often.

Ore - rock that contains minerals from which metal can be extracted profitably.

Carbon - when heated with metal oxide will displace any metal below it in the reactivity series.

changing equilibirum

- temperature

- pressure

- concentration

equilibrium to the LEFT: more reactants than products

equilibrium to the RIGHT: more products than reactants

LE CHATELIER"S PRINCIPLE

when a change is made to the conditions of a reaction at equilibrium the position of equilibrium will change to restore to origional conditions.

increasing temperature

if a reaction is EXOTHERMIC in the forward reaction Le Chateliers principle suggests there will be a decrease in products and increase in reactants.

if the reaction is ENDOTHERMIC in the forward reaction Le Chateliers principle suggests there will be a an increase in products and decrease in reactants.

pressure

if there are more moles of gas reactants - increased pressure leads to more reactants and decreased pressure leads to less reactants. The equilibrium moves to the side with the greater number of moles.

concentration

increased concentration of reactants means more products and increased concentration of products means more reactants.

dynamic equilibrium:

- the rate of the forward reaction and the reverse reaction are equal

- a closed system where the conditions of the reaction are not changed

equilibrium in closed system: no change in the amounts of reactants and products, reactants and products have the same rate of reaction.

- catalyst is a substance that speeds up the rate of reaction without being used up and by lowering the activation energy required for the reaction.

examples of biological catalysts (enzymes): catalase, amylase, chlorophyll

- how much product is made in a set time, how much reactant is used up in a set time

chemical reactions stop when one of the reactants is all used up, always an excess of one of the reactants.

changing temperature: higher temp = more collisions = faster rate

changing concentration: high concentrations of one or both reactants means the particles will be closer together = more collisions = faster rate

changing pressure: particles are closer together = more collisions = faster rate

changing surface area: increased surface area = more particles available = faster rate

metals - lower down the group is more reactive, this is because the lower down the further away the outer shell electron is from the nucleus so it is easier removed. - also the fewer the electrons in the outer shell the more reactive.

metals higher in the reactivity series can displace another metal.

metal + acid = metal salt + hydrogen

metal + water = metal hydroxide + hydrogen

(metal + water = base + hydrogen)

group 1

all have one outer shell electron

desnity increases down the group - more electron shells

reactivity increases down the group - less forces of attraction between nucleus and the electron

group 7

halogens

7 outer shell electrons

low melting and boiling points

not very dense

reactivity increases down the group

group 0

the noble gases

unreactive

identifying gases

oxygen - relights glowing splint

hydrogen - squeaky pop

carbon dioxide - turns limewater cloudy

chlorine - turns coloured litmus paper colourless/white

bacteria

single celled organisms that can reproduce rapidly. bred to survive in high concentrations of metal ions. as they feed they accumulate ions in their cells.

efficient, cheap and not needed to trasnport or use heavy machinary like mining,

phytoextraction

plants genetically engineered to accumulate heavy metals.

cheap but slow

laboratory

small quanities, expensive chemicals, low energy usage, glass equipment, chmists

industry

large quantities, bulk buying chemicals is cheaper, need to reduce energy usage, large scale factory equipment and automated.

life cycle assessment

1) obtain raw material 2) manufacture 3) use 4) disposal

plastic bags - non renewable and non biodegradeable

paper bags - renewable, sustainable and recycleable

recycling: less quarrying for raw materials, less energy extracting from ores, limited oil left, disposal problems reduced

-fossil fuel formed over millions of years, made of hydrocarbons, finite resource, demand is higher than suuply

FRACTIONAL DISTILLATION

- crude oil is made of different hydrocarbons with different boiling points

- all of the hydrocarbons belong to the same homologous series called Alkanes

- the chemical formula for alkanes is Cn H2n+2

crude oil is heated in a fractionating column that has a temperature gradient, it enters the column as a gas. 

small molecules have low boiling points so are collected higher up, large molecules have high boiling points so are collected lower down.

eg. LPG and refinery gases are collected at the top and bitumen is collected at the bottom.

akanes are made of carbon and hydrogen

the longer alkanes have greater intermollecular forces and higher boiling points. they are alos less useful.

smaller alkanes are more useful, eg. petrol.

Cracking is used to break up the longer chains by either using a catalyst or high temperature and pressure, it takes a lot of energy

cracking mates one long alkane into alkanes and an alkene.

alkane: Cn H2n+2

alkene: Cn H2n

today: 78% nitrogen, 21% oxygen and 0.004% carbon dioxide. 

greenhouse effect- the infrared rays are trapped by greenhouse gases and they heat up the world.

climate change:

- due to: burning of fossil fuels, agrricultue, deforestation and growing population

- reduced: fossil fuel dependancy reduced, carbon capture and reduce landfill by recycling.

Pollution: carbon monoxide stops oxygen bonding and suffocates animals, sulfur dioxide causes acid rain, nitrogen oxide produces chemical smog and also acid rain.

particulates - small solid particles that can cause lung problems

potable water - 26% of global population has access to unsafe drinking water.

1) hot volcanic earth released gases and built up the origional gas layer

2) initial atmosphere contained Ammonia, CO2 and water vapour

3) earth cooled and water vapour condensed to form the oceans

4) some of the carbon dioxide dissolved into the water

5) levels of nitrogen increased due to nitrifying bacteria

6) development of plants underwater began to photosynthesise and oxygen was released

7) oxygen was origionally stored in rocks but began to escape into the atmosphere

1) filtered to rid of large objects

2) water in sedimentation tank to remove small particles

3) bacteria added to break down other bacterias

4) fine particles removed by filtration

5) chlorine added to kill bacteria

6) water is ultra filtered and stored in reservoirs

7) treated again before being piped to taps

desalination - basically just extreme evaporation to remove water from salt.