ITOC and Alkanes

describe alkanes

saturated hydrocarbons

what is meant by a homologous series

• a group of organic compounds with the same functional group, same general formula and similar chemical properties.

• they differ by a CH2 unit each time

what is the major use of alkanes

fuels

what is petroleum 

a mixture containing mostly alkane hydrocarbons that can be separated by fractional distillation 

what is meant by unsaturated

contains one or more C=C double bonds

what is meant by saturated

contains only C-C single bonds

what is a fraction

a group of molecules with a similar chain length, Mr and boiling points 

what is fractional distillation

a method of separating crude oil fractions according to their boiling points 

what is a hydrocarbon made from

only hydrogen and carbon

describe the stages of fractional distillation

• crude oil is heated to 350*C, it vaporises and enters the bottom of the column

• the top of the column is cooler than the bottom- negative temperature gradient

• fractions are separated because of their different boiling points

• low boiling point fractions are small molecules/ small Mr are collected at the top of the column

• high boiling point fractions are big molecules/ high Mr are collected at the top of the column

what is the theory behind fractional distillation

• physical process (not chemical)

• separation occurs according to similar boiling point

• weak IMF’s are overcome

• strong covalent bonds are not broken

what happens during cracking

strong C-C covalent bonds are broken

state the economic basis of cracking

• the demand for short chain hydrocarbons is greater than the supply produce from fractional distillation

• cracking breaks down longer, less useful (less profitable) hydrocarbons into shorter more useful, (profitable) products

if asked to write a cracking equation, what is formed

one alkane and one or more alkene/s

what are the conditions and major product of thErmal cracking

• high temperature and high pressure (no values needed)

• alkEnes

what is the major use of the products of thErmal cracking

making polymErs

what are the conditions and major product for cAtylitic cracking 

• high temperatures 

• slight pressure

• zeolite catalyst 

what is the major use of the products of cAtalytic cracking 

• alkAnes 

• Aromatics 

what is the main use for the products of cAtylitic cracking ?

• Automotive fuels 

• Aromatic hydrocarbons for further synthesis 

what is formed during complete combustion of any hydrocarbon ?

• Water

• carbon dioxide

what is needed for complete combustion?

excess oxygen

what condition is needed for incomplete combustion?

limited oxygen

what could form during incomplete combustion to produce a solid pollutant 

carbon particulates (and water)

what could form during incomplete combustion to produce a gaseous pollutant 

carbon monoxide (and water)

list all the potential pollutants from the use. of an internal combustion engine

• carbon particulates (solid)

• CO

• CO2

• oxides of nitrogen (NO and NO2)

list the possible pollutants from burning fossil fuels linked to power stations

oxides of sulfur impurities (SO2 and SO3)

carbon particles

• how are they formed

• effect 

• methods of rejecting/ removing 

• incomplete combustion of fuel 

• causes difficulties breathing/ cardio vascular problems

• filter to remove particulates

unburnt hydrocarbons

• how are they formed

• effect 

• methods of rejecting/ removing 

• incomplete combustion of fuels

• react with NOx in the presence of UV to form low-level ozone which produces photochemical smog —> respiratory problems

• catalytic converters -

C3H8 + 5O ——> 3CO2 + 4H2O

Carbon monoxide

• how are they formed

• effect 

• methods of rejecting/ removing 

• incomplete combustion of fuel

• poisonous gas (combines irreversibly with haemoglobin)

• catalytic converters

2NO   +   2CO —→   N2   +   2CO2

Carbon dioxide

• how are they formed

• effect 

• methods of rejecting/ removing 

• complete combustion of fuels

• green house gas- historic carbon from fossil fuels- contributes to global warming

• use less fuel (walk more) or use alternative fuels such as bioethanol

sulfur dioxides (SOx)

• how are they formed

• effect 

• methods of rejecting/ removing 

• Combustion of impurities in the fuel S + O2 —> SO2 this forms acid rain

• ACID RAIN -

-destroys trees and vegetation

-corrodes buildings

-kills fish in lakes

• SO2 causes breathing difficulties

• use better quality, low sulfur fuels, scrubbers can neutralise SO2 with CAO or CACO3

CaCO3 + SO2 + 2H2O —> CaSO3 + 2H2O + CO2

CaO + SO2 —>CaSO3

Nitrous oxides

• how are they formed

• effect 

• methods of rejecting/ removing 

• N2 and O2 from the air react in high tempratures and pressure inside the engine. N2 + O2 —> 2NO

• reacts with oxygen and water in the atmosphere to produce nitric acid which forms acid rain 

       4NO + 2H2O + 3O2 —> 4HNO3

• catalytic converters 2NO —> N2 + O2