Environmetal Chemitry
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Chemical tests for the presence of water
Anhydrous cobalt (III) chloride —> blue to pink/red Anhydrous copper (II) sulfate —> white to blue
How to test for the purity of water using melting point and boiling point
Mp test - if its pure it’ll melt at 0c, if it’s impure it’ll melt below 0c Bp test - if it’s pure it’ll boil at 100c, if it’s impure it’ll melt boil above 100c
Why is distilled water used in practical chemistry rather than tap water
It contains fewer chemical impurities so it wouldn’t affect the experiment that much if any water was left
Describe the treatment of domestic water (3)
• sedimentation and filtration to remove solids • use of carbon to remove tastes and odours • chlorination to kill microbes (pathogens)
Composition of clean dry air
Nitrogen (N2) - 78% Oxygen (O2) - 21% Mixture of noble gases and carbon dioxide (CO2) - 1%
Source of pollutants (5)
Carbon dioxide (CO2) - complete combustion of carbon-containing fuels Carbon monoxide (CO) and particulates - incomplete combustion of carbon containing fuels Methane - decomposition of vegetation and waste gases from digestion in animals Oxides of nitrogen - car engines Sulfur dioxide - from the combustion of fossil fuels which contain sulfur compounds
Adverse effect of air pollutants (6)
Carbon dioxide (CO2) - higher levels of co2 leading to increased global warming, which leads to climate change Carbon monoxide (CO) - toxic gas —> can kill Particulates - increased risk of respiratory problems and cancer Methane - higher levels of methane leading to increased global warming, which leads to climate change Oxides of nitrogen - acid rain, respiratory problems Sulfur dioxide - acid rain
Strategies to reduce defects of climate change (4)
• planting trees • reduction in life stock farming • decreasing use of fossil fuels • increasing use of hydrogen and renewable energy, e.g. wind, solar
How does planting trees help reduce the effects of climate change
Trees absorb co2 for photosynthesis, reducing the amount of co2 in the atmosphere and lower the greenhouse effect
How does reducing livestock farming help reduce climate change
Livestock (especially cows) produce methane during digestion. Reducing livestock farming decreases methane emissions, lowering global warming contributions
How does decreasing the use of fossil fuels reduce climate change
Burning fossil fuels releases large amounts of co2, using them less lowers co2 emissions and reduces the greenhouse effect
Why does using hydrogen and renewable energy reduce climate change
They produce little to no co2 when generating energy, reducing greenhouse gas emissions from power production
How does using low-sulfur fuels reduce acid rain
Low-sulfur fuels release less sulfur dioxide when burned, lowering the formation of sulfuric acid in rainwater
What is flue gas desulfurisation and how does it help
Power stations pass waste gases over calcium oxide, which reacts with sulfur dioxide to remove it. This prevents so2 from reaching the atmosphere and forming acid rain
How do co2 and methane contribute to global warming
They absorb thermal (infrared) energy radiated from the earth’s surface, then re-emit it in all directions, reducing heat loss to space and warming the atmosphere
How are the oxides of nitrogen formed in car engines
In car engines, high temperatures cause nitrogen and oxygen from the air to react, forming oxides of nitrogen
How do catalytic converters remove oxides of nitrogen
They use catalysts (platinum, rhodium) to convert harmful gases into harmless ones 2CO + 2NO → 2CO₂ + N₂