Combustion of Alkanes

What is a combustion reaction

when a substance burns wiith oxygen to produce (heat) energy and is an exothermic (energy release) process

When a molecule burns completely in oxygen, we say it undergoes……combustion and produces ….and ……..

• complete

• carbon dioxide(g)

• gaseous water (g) state→ water vapour

When a molecule burns INcompletely in oxygen, we say it undergoes……combustion and produces ….and ……… This type of combustion is caused when there …… or we can say……..

• incomplete

• 2 gasses::water vapour (H2O) and carbon monoxide (CO)

• (or) 1 solid: Carbon (C)→ ‘soot’ and 1 gas: water vapour (H2O)

• limited amount of moles of reactant or oxygen

• limiting reactant/agent

what are carbon dioxide and water vapour classed as….

greenhouse gasses

Problems associated with carbon monoxide…

• toxic→ used in natural gas boilers, could be breathed in , causeing reduced amounts of oxygen into lungs and instead CO is absorbed→ could cause so muc harm to be fatal ‘toxic’

• flammable: CO+O2 are very flammable reactions as reacts very easily

Problems with carbon /soot

• Soot (pollutant): formed through small carbon clumps being formed as a result of hhigh temperatures in engines of old cars:

• sootare subalite: easily rise up and build up in the air → eventually this build up : dirty, moky, foggy

• the reuslt is called: Smog(pollution) → reduces the amount of sunlight to the ground making it harder for living things to respired eg plants

-1559.72 kJ/mol

-970.72 kJ/mol

-772.72 kJ/mol

How does complete combustion produce more nergy than incomplete combustion

• makingbonds is an exothermic/energy relaseing process

• ∴ with complete producinf CO2makes 4 bonds relaseing more energy than the products from incoomplete

• we dont accound for H2o number of bonds as this is formed regardless of which type of combbustion

Why is omplete combustion less expensive

bcs we need to burn the same amount of fuel to get more energy

what organic compounds do the impurities form in the alkane eg) CH4S form in complete combustion ……

give the mollecule and state of what these would form : S, N, Si

CH4S + 3O2→ CO2+2H2O+SO2(g)

• SO2(g)

• NO(g)

• SiO2(s)

id teh equaton doesnt spedify what type oof combustion to use…

automatically assumecomplete combustion

Unwanted organic compounds found in fuels are called… and these make fuel /// ///// than////// as some still remain in the fuel

• impurities

• less efficient

• compleye combustion of alkenes

why is sulphur dioxide a pollutant

• causes respurutaroy issues/,akes it harder to breathe in high concentrations

• So2(g) + H2O(g) → H2SO4 (l) ∴ when sulphur dioxide reacts with oxygen produces sulphuric acid→ ‘acid rain’

why is acid rain bad

• ↑ acidicty in soil making it harder frocrops to grow

• ↑ acidicty in rivers/ponds ect which denature bacteria and kill wildlife by making habitat difficult to live in