Fossil Fuels Products Flashcards
gather and present information from first-hand or secondary sources to write equations to represent all chemical reactions encountered in the HSC course
It is recommended that you write equations to represent the chemical reactions as you gather information about them throughout this section of the module. The information needed to write the equations might be gathered from first-hand investigations. You should check these against equations published in secondary sources. For other reactions studied, write equations as a summary of the chemistry involved.
When presenting equations in carbon chemistry, the emphasis is on showing the structures of reactants and products, not on making sure that they are balanced. The emphasis for this section of the syllabus is in showing structure rather than in balancing equations.
The following are the equations that represent the processes presented in this section of the syllabus:
Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum
Petroleum is a mixture of hydrocarbons. When petroleum undergoes fractional distillation, some fractions, particularly petrol, are in demand and of high economic value. Other fractions, consisting of larger molecules than in petrol and of low value, can be passed over a heated catalyst that cracks the larger molecules into smaller molecules. A major by-product of this catalytic cracking is ethylene, also known as ethene.
Ethene composition
Another way ethylene is produced . . .
A process called steam thermal cracking is the main source of ethylene throughout the world. In this process ethane (C2H6) gas from natural gas, or larger hydrocarbons in low value petroleum fractions, are mixed with steam and passed through hot metal coils. The steam removes carbon deposits from the metal coils. The heat from the coils breaks bonds to change the ethane, or the larger hydrocarbons, to ethylene.
identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products
Ethylene can be transformed into many useful products because of the high reactivity of its double bond.
An explanation
Alkenes are more chemically reactive than their corresponding alkanes. The yellow colour of bromine water, which is due to the presence of bromine, is lost when the bromine water comes in contact with an alkene, but not when in contact with an alkane. This demonstrates the high reactivity of a
C=C in an alkene compared with the C-C in an alkane.
Some of the useful products made from ethylene are:
Product Formula Use polyethylene (CH2)n plastic ethylene oxide (CH2)2O steriliser ethanol C2H5OH disinfectant ethanoic acid CH3COOH food preservative
identify that ethylene serves as a monomer from which polymers are made
Ethylene is polymerised to polyethylene
Equation showing ethylene polymerised to polyethylene
High pressures within the reaction vessel produce soft, low density polyethylene (LDPE) consisting of tangled polymer chains (with molecular masses 100 000); used in crinkly plastic bags as used for heavy duty garbage bags.
identify polyethylene as an addition polymer and explain the meaning of this term
Polyethylene is called an addition polymer.
An addition polymer forms when small molecules (the monomer), such as ethylene, add together to form long molecules (the polymer), such as polyethylene, and no other product.
outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer
Two different forms of polyethylene can be manufactured, depending on the reaction conditions.
To produce low density polyethylene (LDPE), a peroxide containing an O-O bond that breaks easily forming free radicals is used to initiate the joining of ethylene monomers. The process must occur under high gas pressure to produce LDPE. These production conditions result in molecules with the short branches that characterise LDPE.
To produce high density polyethylene (HDPE), low gas pressures and a catalysts made of transition metals and organometallic compounds enables more ordered orientation of ethylene to form the long unbranched and aligned molecules in HDPE.
Identity following as commercially significant monomers:
vinyl chloride
styrene
by both their systematic and common names
describe the uses of the polymers made from the above monomers in terms of their properties
The following information addresses the above two syllabus points at the same time.
The table below provides the systematic and common names for some commercially significant monomers. The table describes the properties that account for the uses of some polymers produced from the selected monomers.
MONOMERS POLYMERS
Common name Systematic name Name Properties Used for
ethylene ethene LD polyethylene low density, soft flexible food bags
HD polyethylene high density, hard crinkly garbage bags
vinyl chloride
chloroethene polyvinylchloride made rigid and flame resistant with additives, water resistant rigid pipes and gutters,
flexible raincoats and shower curtains
styrene
ethenylbenzene polystyrene transparent, due to few crystals,
when gas added forms foam compact disc cases,
heat insulation, floats
Expanded polystyrene is made by producing gas bubbles inside polystyrene. The low density of expanded polystyrene is used in flotation devices. The trapped gas spaces make it an excellent insulator.
construct word and balanced formulae equations of chemical reactions as they are encountered
An important part of the Preliminary course, that you must continue with throughout the HSC course, is learning how to:
construct word equations, e.g: methane + oxygen —–> carbon dioxide + water
and
balance formulae equations, e.g: CH4 + 2O2 —–> CO2 + 2H2O
You must be able to do this for the reactions you encounter in every module that you study, core and option.
There are three important steps involved:
Show all reactants and all products in the word equation.
Write the correct formula for each reactant and each product.
Balance the formula equation by placing coefficients (numbers) in front of formulas so that you have the same total number of each kind of atom on both the reactant side and the product side. Remember that in chemical reactions atoms are just rearranged, not created or destroyed.
