4B.2 Alkanes as fuels Flashcards
what is combustion
it is a chemical reaction in which a compound reacts with oxygen
what are the products of combustion
- H2O
2. CO2
which product of combustion is bad and why
CO2 because it is a greenhouse gas that contributes to global warming and climate change
how does carbon dioxide work
it works by trapping the infrared radiation emitted from the earth surface stopping it from escaping the earth
what is complete combustion
it is a reaction in which all the atoms in fuel are fully oxidized, producing only carbon dioxide and water
what is incomplete combustion
reaction in which some of the atoms in the fuel are not fully oxidized producing carbon dioxide, carbon monoxide, and soot (unburnt carbon)
why may incomplete combustion reactions occur
because there isn’t enough oxygen present, or because the combustion is very rapid
what is an example of soot forming
C3H8 + 4O2 ——> C + 2CO + 4H2O
how toxic is soot
it can be harmful but not fatal
example of the formation of CO
C3H8 + 4O2 ——> 2CO + CO2 + 4H2O
How toxic is carbon monoxide
it is fatal
what is carbon monoxide
it is a colourless odourless toxic gas that causes the death of people each year. it acts by preventing the transport of oxygen around the body
what are unburned hydrocarbons
they are products of incomplete combustion where the hydrocarbon itself isn’t burned at all, resulting in a tiny portion of unchanged hydrocarbon being released into the atmosphere
what are oxides of sulfur
some molecules in crude oil might have sulfur impurities that can’t be removed by reforming, cracking, and fractional distillation. when the crud email undergoes combustion some of the sulfur might react with the oxygen forming SO2 and 2SO3 which are both acidic oxides so when released into the atmosphere they can dissolve in water to form sulfurous acid H2SO3 and sulfuric acid H2SO4 which both contribute to acidic rain that can damage the aquatic life and the growing of crops
what is the equation for the oxidation of sulfur
S + O2 ——> SO2
what is the equation for the oxidation of sulfur oxide
2SO2 + O2 —–> 2SO3
What is the equation for SO2 dissolving in water
SO2 + H2O —–> H2SO3
What is the equation for SO3 dissolving in water?
SO3 + H2O —–> H2SO4
oxides of nitrogen
very small molecules of alkanes can include nitrogen atoms (even thoughit is very unlikely to use alkanes that include nitrogen as a fuel). so in composition under very high temperatures (especially in car spark plugs) the nitrogen from the air can react with oxygen causing nitrogen oxide. which are represented with the formula of NOx Now we can have a lot of nitrogen oxides but the ones formed in the reaction are nitrogen monoxide and nitrogen dioxide. Carbon dioxide is an acidic oxide so when it is dissolved in water it can form nitrous and nitric acid affecting the equate life and damaging the crops and forests
what is the equation of oxidation of Nitrogen
N2 + O2 —–> 2NO
what is the equation of oxidation of Nitrogen monooxide
2NO + O2 —–> 2NO2
What is the equation for 2NO2 dissolving in water
2NO2 + H2O ——–> HNO2 + HNO3
What are catalytic converters
they are devices that are fitted near the exhaust system that convert toxic materials of incomplete combustion to normal materials they are made up of precious metals such as, platinum, rhodium, and palladium, which are spread over a tiny honeycomb mush to increase the surface area and to save money
what is the three-way catalyst
a type of catalytic converter that can remove carbon monoxide, unburnt hydrocarbons, and oxides of nitrogens
what are the three reactions that occur in the three-way catalyst
1. oxidation of unburned hydrocarbons: C8H18 + 12.5O ------> 8CO2 + 9H2O 2. oxidation of carbon monoxide: 2CO2 + O2 ------> 2CO2 3. 2NO + 2CO -----> N2 + 2CO2
what is the best way to deal with sulfur oxides
by removing sulfur before using the fuel
