chemistry definitions Flashcards
what is meant by air pollution?
it is the condition in which air contains high concentration of chemicals that may harm living things or damage non-living things
what is the composition of air?
78% nitrogen
21% oxygen
1% other gases
- 0.03% carbon dioxide
- 0.97% noble gases (mainly argon)
how is air separated? collecting oxygen/nitrogen
by the fractional distillation of liquified air
- they are first cooled and compressed, making molecules move closer
- this forms liquified air
what is the source of carbon monoxide?
incomplete combustion of carbon containing compounds (petrol) in car engines
they are colourless and odourless, making it hard to be detected
what is the effect of carbon monoxide?
it combined irreversibly with haemoglobin in blood, forming stable carboxyhaemoglobin, which prevents oxygenated blood from being transported to different part of the body, depriving them from oxygen
- causes breathing difficulties, fatigue, and death
what can be used to reduce the carbon monoxide production?
catalytic converters converts carbon monoxide into less harmful gases such as carbon dioxide
(CO is oxidised)
2CO (g) + O2 (g) = 2CO2 (g)
what is the source of nitrogen oxides?
- lightning activity where thermal energy is released, causing nitrogen and oxygen in the air to react together because of the high temperature
- nitrogen and oxygen in air combined to form carbon monoxide at high temperatures (in chemical factories/car engines)
nitrogen will react with oxygen to form nitrogen monoxide
nitrogen monoxide will react with oxygen to form nitrogen dioxide (brown in colour)
what are the effects of nitrogen oxides?
-they can cause irritation to the eyes, lungs, and skin- high levels of oxides of nitrogen will result in the inflammation of lungs (bronchitis)
-forms petrochemical smog
- acid rain, where they react with water in the atmosphere to form nitric acid
4NO2 + O2 + 2H2O = 4HNO3
how do we reduce the emission of oxides of nitrogen?
catalytic converters are used to remove oxides of nitrogen to form N2
what is the source of sulfid dioxides?
combustion of fossil fuels such as coal and crude oil which contain sulfid as an impurity
- S + O2 = SO2
volcanic eruptions
what are the effects of sulfur dioxide?
- acid rain
• sulfur dioxide in the air will dissolve in water in the atmosphere, forming sulfurous acid
• sulfurous acid will react will be oxidised to form sulfuric acid - irritates eyes,lungs, causing breathing difficulties. high levels of SO2 will result in the inflammation of lungs (bronchitis)
why is the pH level of unpolluted rainwater slightly below 7?
this is because carbon dioxide in the air will dissolve in water in the atmosphere, forming carbonic acid, which is a weak acid
source of unburnt hydrocarbons?
hydrocarbons that have not been burnt in vehicle engines and are released in car exhaust fumes and chemical plants
effects of unburnt hydrocarbons?
carcinogenic (causes cancer)
will react with oxides of nitrogen, forming ozone
sources of methane
when plants or dead matter decay, also released from cows and other farm animals due to the digestion of food (from their farts)
decay of rubbish in landfills
effects of methane
contributes to global warming because methane is a greenhouse gas
sources of ozone
when nitrogen dioxide in the air reacts with unburnt hydrocarbons in the presence of SUNLIGHT
effects of ozone
irritates eyes, lungs, throat, causing breathing difficulties
asthma inducing
produces petrochemical smog because sunlight acts on air and other pollutants
damages plant crops
chemical equations in the catalytic converter
- hot exhaust gases such as unburnt hydrocarbons, oxides of nitrogen and carbon monoxide are passed into catalytic converters that are fitted into car engines which are covered with platinum and rhodium catalysts
these harmful gases are converted into harmless compounds by redox reactions
- carbon monoxide is oxidised into carbon dioxide
• 2CO + O2 = 2CO2 - carbon monoxide and nitrogen oxides will react in the presence of the platinum and rhodium catalysts where nitrogen monoxide is reduced to nitrogen and carbon dioxide
• 2CO + 2NO = N2 + 2CO2 - unburnt hydrocarbons such as octane will be oxidised to form carbon dioxide, and water
• 2C8H18 + 25O2 = 16CO2 + 18H2O
how do we reduce air pollution my motor vehicles?
using cleaner fuels such as hydrogen, because when hydrogen burns, only water is produced
use electric cars, reducing exhaust gas emissions
chemical equations in flue gas desulfurisation
- as sulfur dioxide is being passed into the plant, it reacts with an aqueous suspension of calcium carbonate to form solid calcium sulfite and carbon dioxide gas
CaCO3 (s) + SO2 (g) = CaSO3 (s) + CO2 (g)
2 . calcium sulfite is further oxidised to form calcium sulfate (neutral)
2CaSO3 (s) + O2 (g) = 2CaSO4 (s)
what are CFCs? chlorofluorocarbons
compounds that contain the elements carbon, fluorine, chlorine
why is the ozone layer important?
absorbs UV radiation and blocks it from our skin to prevent skin cancer/ genetic mutations
what is the carbon cycle?
it is a mechanism that maintains the level of carbon dioxide in the atmosphere
