C6 - Chemistry Out There

Anode: 2O2- - 4e- –> O2 Cathode: Al2+ + 2e- –> Al

The decomposition of a liquid by passing an electric current through it

Cathode: hydrogen Anode: hydroxide (water and oxygen bubbles form)

2H+ + 2e- –> H2 4OH- - 2e –> OH-

The current and the time taken - each one is directly proportional to the amount of product made during electrolysis

Cation: Pb2+ Anion: Br- Lead formed at cathode, bromine formed at anode Pb2+ + 2e- –> Pb 2Br- - 2e- –> Br2

1) 1.5 hours 2) 2.5A

The reactants have greater energy than the products - energy is given out to the environment during the reaction

The reactants have less energy than the products - energy is taken in from the environment during the reaction

The fuel used is hydrogen and as it enters the cell at the anode. The hydrogen is forced through the catalyst and splits into two H+ ions and two electrons. The protons diffuse through the proton exchange membrane. The unused hydrogen leaves the cell before going through. The electrons can’t diffuse through so go through the electric circuit and produce the current to power the cell. The hydrogen ions that diffuse through react with the oxygen that enters at the cathode to produce water, which is the waste product. A hot phosphoric acid catalyst is needed in this reaction.

2H2+O2 –> 2H2O

Anode: H2 - 2e- –> H+ 2H2O

• They’re lightweight • The water (waste product) can be drunk by the men on a manned spacecraft • They’re compact • They have no moving parts

• Fuel cells don’t release harmful waste products (such as CO2), so don’t contribute to global warming and the greenhouse gases • There’s a large potential source of hydrogen - the water can be decomposed by electrolysis to produce even more hydrogen • The stages in producing a fuel cell are more efficient than conventional fuels - electrical energy transferred directly when required • The catalyst in hydrogen fuel cells are often poisonous • Most of the world’s hydrogen production is done using fossil fuels (reacting steam with coal or natural gas) - this produces CO2 emissions

A vigorous exothermic reaction between aluminium and iron (III) oxide that produces aluminium oxide and iron. The iron (III) oxide loses oxygen, so is reduced to iron - this melts. The aluminium gains oxygen, so is oxidised to aluminium oxide. 2Al2 + Fe3O3 –> Al2O3 + 3Fe

Reducing Agent - substance that causes the other to be reduced (gain electrons/lose oxygen) Oxidising Agent - substance that causes the other to be oxidised (lose electrons/gain oxygen)

• Magnesium • Zinc • Iron • Tin • Copper

Fe(NO3)3 + Mg --> Fe + Mg(NO3)2 Fe3+ + 3e- --> Fe - reduced Mg - 2e- --> Mg2+ - oxidised Specator ions = NO3- The reducing agent is Magnesium and the oxidising agent is Iron.

Oxygen and water

iron + oxygen + water –> hydrated iron (III) oxide The iron is oxidised to form Fe3+ ions, and the oxygen is reduced to form oxide (O2-) ions

• Coat with a layer of paint • Coat with a layer of oil or grease • Galvanising - add a layer of zinc • Using alloys of the iron - adding carbon or chromium

A layer of either zinc or tin is added to the iron. This ensures that when the material is exposed to air and water, the air and water reacts with the layer instead of the iron. Therefore, the zinc or tin is rusted instead of the iron - thus sacrificing itself. However, if the tin layer is scratched and the iron exposed, the iron will rust faster as iron is more reactive than tin. If zinc is used then the iron won’t be reacted with regardless, as zinc is more reactive than iron and is reacted with in preference.

• Common drinking alcohol • Fuel • Solvent in perfumes and aftershaves

It contains carbon, excluding CO2 and carbonate substances