Chem Module A Notes Essay

Submitted By georgiameagher
Words: 9908
Pages: 40

Required Knowledge (Preliminary Course)
Energy from Fossil Fuels
Originates from sun - solar to chemical by photosynthesis.
Red and violet wavelengths of sunlight absorbed by pigment chlorophyll, energy converted to chemical energy in glucose.
Glucose – carbohydrate: high-energy compound of C, H and O.
6CO2(g) + 6H2O(l) + energy  C6H12O6(aq) + 6O2(g)
Petroleum consists of cruide oil and natural gas, formed of remains of single-celled marine organisms.
Quick burial, decay by bacteria without presence of oxygen, millions of years of heat and pressure caused by overlaying sediments convert to petroleum.
Mixture of 300 hydrocarbons, sulfur and nitrogen compounds.

The various Fractions from Crude Oil and their uses


Carbon Compounds
C forms many compounds because of properties:
4 valence electrons so can form 4 strong covalent bonds, which can be single, double or triple.
Saturated: only single (ethane).
Unsaturated: double or triple (ethane, ethyne)
Can join onto other C atoms to form chains (branched or straight) and rings.
Can form strong covalent bonds with other non-metals (H, O, N, halogens)
Functional group: grouping of atoms that is common to all members of that series (single bond, double bond, -O-H group).
Combustion produces CO2 and H2O, and in limited supply of O2 can produce C or CO.

Bonding in Carbon Compounds
Intramolecular
Intermolecular
Determine physical properties.
Covalent bonds: atoms of non-metals formed by sharing pairs of electrons.
Polar if atoms sharing electrons are different or non-polar if atoms sharing electrons are identical (H2).
More electronegative: atom that attracts electrons more strongly.

Dispersion forces: weak, temporary forces of attraction that exist due to constantly moving electron clouds.
Dipole-dipole forces: permanent, electrostatic attractions between positive and negative ends of polar molecules.
Hydrogen bonds: F, O and N.


1 Fossil fuels provide both energy and raw materials such as ethylene, for the production of other substances
1.2.1 Construct word and balanced formulae equations of chemical reactions as they are encountered

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1.2.2 Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum
Petroleum
Petroleum: mixture of hydrocarbons, consisting of liquid crude oil and gaseous natural petroleum gas.
Liquid crude oil can be seperated into a series of fractions: molecules with similar molecular weight, by fractional distillation.
Fractions of Crude Oil and Uses
Name
BP (no. of carbon atoms)
Use
Gases
triple > single
Ethylene (C2H4), simplest unsaturated solution
Contains highly reactive double bond – one of bonds readily breaks to react quickly and easily with other molecules.



Ethylene  ethanol
Industrial
Laboratory
Heating with water (steam) at 300C, high pressure, using concentrated phosphoric acid as catalyst.

Regarded as an alkanol: alkanes with H atom replaced by OH function group.

Heating with dilute H2SO4 (the H+ ions being the catalyst).
Works for all liquid alkenes converted to corresponding alkanols.
E.g. 3-hexene converted to 3-hexanol



Hydration reaction: addition of water molecule across a double bond.
Industry - reactant and solvent in synthesis of products; pharmaceuticals and perfumes, varnishes and plastics.
Home – antiseptic, solvent in food colorings and flavorings.

Oxidation of ethylene
Ethylene glycol (1,2 – ethanediol)
Ethylene oxide used as fumigant, but large amounts converted.

Used in manufacture of polymers (polyester fibres and plastics) and as antifreeze.

Other catalyzed reactions of ethylene
Used to convert ethylene into the starting materials for making a variety of other plastics.
E.g. Form vinyl chloride, the starting material for common plastic poly(vinyl chloride) or PVC.


Most important reaction of ethylene is conversion to polyethylene…