10 Chemistry of the Environment
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Cobalt Chloride test for water
Blue when anhydrous, Pink when hydrated
test for purity of water
boils at exactly 100C
Why is distilled water used in practical chemistry rather than tap water
Distilled water contains less impurities
What will water from natural sources contain?
dissolved oxygen, metal compounds, plastics, sewage, harmful microbes, nitrates from fertilisers, phosphates from fertilisers and detergents
What are the beneficial impurities that water from natural resources contain
• dissolved oxygen for aquatic life • some metal compounds provide essential minerals for life
What are the harmful impurities that water from natural resources contain
• some metal compounds are toxic, • some plastics harm aquatic life • sewage contains harmful microbes which cause disease • nitrates and phosphates lead to deoxygenation of water and damage to aquatic life
treatment of the domestic water
1) sedimentation and filtration to remove solids 2) use of carbon to remove tastes and odours 3) chlorination to kill microbes
What are used as fertilisers?
Ammonium, phosphates, nitrates and potassium salts
Composition of gases in the air:
Nitrogen 78%, Oxygen 21%, Argon 0.9%, Carbon dioxide 0.04%
Source of carbon dioxide
Complete combustion of carbon containing fuels
Source of carbon monoxide
Incomplete combustion of carbon-containing fuels
Source of methane
Decomposition of vegetation and waste gases from digestion in animals
Source of nitrogen oxides
combustion of air at high temperatures in car engines or produced during thunder storms
Source of sulfur dioxide
combustion of fossil fuels which contain sulfur compounds
Adverse effects of Carbon dioxide
increased global warming which leads to climate change
Adverse effects of carbon monoxide
toxic gas - binds to haemoglobin in the blood, reducing the ability of blood to carry oxygen
Adverse effects of particulates (e.g. carbon)
increased risk of respiratory problems and cancer
Adverse effects of methane
increased global warming, which leads to climate change
Adverse effects of oxides of nitrogen
acid rain, photochemical smog, respiratory problems
Adverse effects of sulfur dioxide
acid rain
How to reduce the effects of cllimate change?
planting trees, reduction in livestock farming, decreasing use of fossil fuels, increasing use of hydrogen and renewable energy
How to reduce the effects of acid rain?
a) use of catalytic converters in vehicles - removes oxides of nitrogen b) reducing emissions of sulfur dioxide by using low-sulfur fuels c) flue gas desulfurisation with calcium oxide - reacting SO2 with CaO to remove it from the flue gas
photosynthesis
reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light
Explain how oxides of nitrogen form in car engines and describe their removal by catalytic converters
The high temperature and pressure inside an internal combustion engine causes nitrogen and oxygen to combine. A mixture of different nitrogen oxides are then formed. To remove carbon monoxide and nitrogen oxides, a catalytic converter can be fitted to a car exhaust. By converting the oxides of nitrogen into carbon dioxide and nitrogen. 2CO + 2NO → 2CO2 + N2