Alkanes as fuels Flashcards
What are the products of the complete combustion of alkanes?
carbon dioxide and water
what is the equation for the complete combustion of propane? BALANCE IT!
C3H8 + 5O2 = 3CO2 + 4H2O
Wat can the products of incomplete combustion be?
Carbon dioxide, water, carbon monoxide, carbon and unburned hydrocarbons
How can you tell carbon is being produced in incomplete combustion?
Smoke or soot being produced.
why is carbon monoxide dangerous?
it binds to haemoglobin in red blood cells which stops the body from taking in enough oxygen
what is the notation used for unburned hydrocarbons?
HC
why is sulfur in crude oil potentially dangerous?
if not removed during distillation, cracking or reforming, sulfur in compounds can be burned and form sulfur dioxide, then react with the atmosphere to form sulfur trioxide.these gases can then dissolve in water to form acids
what acid is formed when sulfur trioxide dissolves in water?
sulfuric acid
what acid is formed when sulfur dioxide dissolves in water?
sulphurous acid
why are oxides of nitrogen quite rare compared to oxides of sulfur?
their combustion occurs at high temperatures, such as the spark plugs in cars
how are oxides of nitrogen formed?
nitrogen in alkane fuels react with oxygen molecules in the air under high temperatures
what are the three steps from nitrogen to react to form nitrous and nitric acids?
N2 + O2 = 2NO (Nitrogen monoxide formed)
2NO + O2 = 2NO2 (acidic nitrogen dioxide is produced)
2NO2 + H2O = HNO2 + HNO3 (nitrous and nitric acids formed)
what precious metals act as catalysts in catalytic converters?
platinum, rhodium and palladium
what is the internal structure of catalytic converters?
metal catalyst spread over a honeycomb structure to increase surface area and save money.
what gases do three-way catalysts remove?
carbon monoxide, unburned hydrocarbons and oxides of nitrogen
what is complete combustion?
means all the atoms in the fuel are fully oxidised
what is incomplete combustion
means that only some of the atoms in the fuel are fully oxidised
the world has fewer uses for
longer-chained hydrocarbons, so there is a surplus of them
the demand for shorter chained hydrocarbons is higher because
they are better fuels and can be used to make other substances such as polymers
cracking causes
larger molecules to break into smaller ones
octane is used
as one of the hydrocarbons in petrol
ethene is used
to make polymers
the combustion is engines is
very rapid
in engine combustion, not all
hydrocarbons of the right size burn the way
hydrocarbons with……chains burn less efficiently than those with………………………………..
straight chains ……..with branched chains or cyclic compounds
when pentane is converted in reforming, what is produced?
cyclopentane and hydrogen gas
fractional distillation and cracking are different because
fractional distillation involves separating a mixture while cracking involves making new compounds
propane is used as
fuel for homes and when camping, sold in high pressure containers
the complete combustion of alkanes produces
water and carbon dioxide
the products of complete combustion of alkanes are problematic because
carbon dioxide is a greenhouse gas which contributes to the enhanced greenhouse effect, which contributes to climate change
combustion of alkanes can also produce other compounds such as
carbon monoxide, carbon, unburned hydrocarbons, oxides of sulfur and oxides of nitrogen
the combustion of alkanes can be incomplete because
there is insufficient oxygen present or because combustion is very rapid
all of the hydrogen atoms in an alkane molecule is converted to ….. during combustion
water
incomplete combustion forms
solid carbon as soot or smoke
carbon monoxide is (physical properties)
colourless and odourless
catalytic converters used currently are not very efficient at removing
sulfur compounds
the best way to remove sulfur pollutants are to
remove sulfur compounds from the fuel before combustion
