Air & Water Flashcards
What is coal gasification?
The process of producing syngas from coal, water, and oxygen
What is syngas?
A raw material that can be used as a fuel or to produce useful chemicals
Benefit of using hydrogen as a fuel
It is environmentally-friendly since it only releases H2O as a product
Source of hydrogen
- steam reformation of methane
- cracking of hydrocarbons
Percentage of nitrogen in air:
79%
Percentage of oxygen in air
20%
Percentage of carbon dioxide in air:
0.3%
Results of fractional distillation of air:
- Oxygen
- Argon
- Nitrogen
Uses of oxygen
- making steel
- oxygen tents in hospitals
- oxy-acetylene flames in welding
- oxygen cylinders for divers/high-altitude mountaineers
Source of carbon monoxide
Incomplete combustion of compounds containing carbon
Includes: petrol, coal, oil, gas
Effect of carbon monoxide
Reduces the ability of blood to carry oxygen.
Instead of oxyhemoglobin, it becomes carboxyhaemoglobin.
Source of lead compounds:
Car exhausts. It is formed through the combustion of petrol containing lead.
Harmful effects of lead compounds
Causes lead poisoning, which may lead to brain damage
Sources of methane
- bacterial decay of vegetable matter
- waste gases from digestion in animals
Harmful effects of methane
Greenhouse gas
Source of ozone
Photochemical reactions
Harmful effects of ozone
reacts with unburned hydrocarbons to form photochemical smog, which causes respiration problems
Source of unburned hydrocarbons
- incomplete combustion of petrol in internal combustion engines of cars
- leakage from petrol tanks in vehicles (petrol vaporises and escapes)
Harmful effects of hydrocarbons
Some hydrocarbons are toxic and can disrupt healthy cell growth in small children
Source of sulphur dioxide
- burning of fossil fuels containing sulphur compounds
- volcanic eruptions
Harmful effects of sulphur dioxide
Causes acid rain
Source of nitrogen oxides
- combustion of fuel in internal combustion engines at high temperatures
- lightning activity
Harmful effects of nitrogen oxides
- acid rain
- catalyses the photochemical formation of ozone
Effects of acid rain:
- erosion of steel/concrete structures
- increased soil acidity
- lower pH levels in lakes/streams
- aquatic life affected
Uses of calcium carbonate
- reduces acidity
- desulphurisation: removes SO2 in flue gas
What does a catalytic converter do?
Redox reactions:
- nitrogen oxide to nitrogen
- carbon monoxide to CO2
- unburned hydrocarbons to CO2 and H2O
Examples of greenhouse gases and their sources:
- CO2 from combustion of fossil fuels
- methane from rotting vegetation
- CFC from aerosol propellants/refrigerants
Describe the greenhouse effect
Greenhouse gases absorb the heat energy radiated back from the earth’s surface so that the heat is retained. As a result, the surface temperature increases.
Sources of CFC
- aerosol propellants
- refrigerants
Harmful effects of CFC
- The high-energy radiation breaks carbon’s bonds with chlorine
- Chlorine proceeds to bond with oxygen from the ozone layer, effectively destroying ozone molecules
What does the ozone layer do?
Prevents high-energy UV radiation from penetrating to the earth’s surface
Composition of natural water and their contents:
- rain-water: made up of dissolved gases
- rain-water (industrial areas): made up of dissolved pollutants
- rain-water (becomes surface water): contains mineral salts, organic matter, etc
- surface water (agricultural lands): contains nitrates and phosphates from fertilisers leached from the soil
Effects of water pollutants:
- metal poisoning
- nitrates interfere with haemoglobin’a ability to carry oxygen
- nitrates and phosphates cause eutrophication
Uses of water:
- food/car manufacturing: washing and cleaning
- steel mills+power stations: cooling purposes
- soft drinks: food processing
Describe the water purification process:
- Coagulation
- Sedimentation
- Filtration
- Chlorination
Why is alum used in water purification processes?
Coagulating small particles to make big solid lumps
Why is lime used in water purification processes?
To neutralise acidic impurities
Products of complete combustion of fossil fuels
CO2/CO and H2O
