developing fuels

• Petrol and diesel produce particulates, which are made in incomplete combustion and cause respiratory illnesses and blackening of buildings.
• Petrol and diesel also produce unburnt fuels, which are wasteful and inefficient in engines.
• CO is a pollutant produced by petrol and diesel due to incomplete combustion, which is toxic.
• CO2 is a pollutant produced by petrol and diesel, made in complete and incomplete combustion, which contributes to global warming.
• SOx is a pollutant produced by petrol and diesel, caused by sulfur impurities and oxygen in the air, which is toxic and causes respiratory illnesses.
• NOx is a pollutant produced by petrol and diesel, caused by nitrogen and oxygen in the air, which forms photochemical smog and is bad for people with respiratory illnesses.
• Ozone, O3, is a pollutant produced by petrol and diesel, which is photochemical smog at ground level, is toxic and an irritant.
• the use of hydrogen as a fuel (created by hydrolysis of water) is more sustainable because it is a renewable resource, it doesn’t produce CO2/CO/C. However electricity is required which indirectly burns fossil fuels and it’s less energy dense than petrol.
• ethanol is a more sustainable option than petrol as it can be made from plants by fermentation, it’s renewable, produces less emission as it completely combusts due to oxygen being in it, no SOx. However it’s not fully carbon neutral due to transport and production of plants and you still get NOx so still need a catalytic converter.
• HDPE (high density polyethene) has a high density structure with loads of strong intermolecular forces (crosslinks) and a high melting point and LDPE has a low density structure with weaker intermolecular forces, which is why they’re more flexible.
• electrophiles are short of electrons so they accept electrons in pairs or singles from a donor and they react with alkenes. Alkenes undergo electrophilic addition with electrophiles, this happens in stages called reaction mechanisms.
• alkenes react with Br2 at room temperature to form a dibromo compound. 


  alkenes also react with HBr at room temp to form a bromo compound.
• alkenes react with H2O with a concentrated sulfuric acid catalyst, heat, pressure and steam to form an alcohol (OH). 


  alkenes react with H2 with a nickel catalyst, heat and pressure to form and alkane
• the evidence for electrophilic addition is that if you react an alkene with an electrophile in NaCl, the alkene will react with the electrophile first rather than the NaCl because the Br forms a stronger bond with the carbon and then the Cl reacts with the carbocation to form a bromo, chloro compound as well as NaBr
• sigma bonds are stronger than pi bonds because it’s directly between atoms whereas pi bonds are weaker because in a double bond they can be either above or below the sigma bond, meaning it’s further away from the central atom. this is what makes alkenes highly reactive.
• when naming alkenes, you prioritise the double bond in which carbon it is on, choose the lowest number then work out the side chains from there. If there’s more than one double bond you add an “-a” to the end of the name ( but-1,3 diene). 2 double bonds = diene. 3 double bonds = triene. 4 double bonds = tetrene.
• stereoisomers exist because alkenes show a restricted rotation around the C=C double bond, therefore bonds need to be broken in order to make a new arrangement so these other arrangements exist as their own. Z/cis = same side, E/trans = opposite side. they have the same molecular formula but different structural formula/arrangement.
• catalysts provide an alternate pathway of lower activation energy to speed up the reaction. they remain chemically unchanged after a reaction. they can receive or gain electrons, transition metals are good catalysts as they have variable oxidation states. Homogeneous = same state as reactants. Heterogeneous = different state.
• Heterogeneous catalysts:

  • reactants adsorb to the catalyst active site
  • bonds weaken within the molecule as bonds form between the reactants and the catalyst and they get stronger.
  • this allows a reaction to happen at a lower activation energy as not as much energy is needed to break the weaker bonds, so new bonds are formed between the two different reactants to make the product which deadsorbs from the catalyst and diffuses
• if a catalyst is poisoned it means that it is permanently binded to the active site due to stronger attraction, blocking the active site from the reactants.
• catalytic converters are needed in an exhaust to remove harmful gases from being released.

  • CO + NOx ———> CO2 + N2

  the catalyst coats a honeycomb-like structure for an increased surface area.
• cracking is when a long chain alkane is broken down into useful shorter chain alkane and alkene. it’s a thermal decomposition reaction. a hazard in the practical is suck back which is avoided by continuing to heat the tube until the tube is removed from the water. also alkanes are flammable so avoid contact with naked flame.
• naming alkanes:

  1. identify longest carbon chain (eg. hexane)
  2. identify side chains (eg. 2 carbons on side chain = ethyl)
  3. number of side chains (eg. di, tri, tetra)
  4. which carbon the side chains are on