10. Chemistry Of The Enviroment Flashcards
Describe the composition of clean, dry air
78% Nitrogen
21% Oxygen
1% other variable gases (0.9% Argon, 0.04% CO2)
What are permanent gases + 2 Eg.s
Gases that cannot be liquefied by pressure alone at normal temperatures
Oxygen and nitrogen
What is fractional distillation used for in environmental chemistry
To separate oxygen from liquified air
What is fractional distillation used for
To separate oxygen from liquid air
Variable gases
Name 7 and what they do
Their concentration varies according to place and time
Argon (0.9%), CO2(0.04%), Nitrogen oxides, Helium, hydrogen, methane, neon
How gases are produced
Fractional distillation of air
What fractional is used for
P\producing gases by separating oxygen from liquid air
Industrial preparation of gases(3)
Pure air is liquified under high pressure and low temperatures (-200*)
Purified air contains nitrogen, argon and oxygen
Temperature is increased causing nitrogen to vapourise first, argon second and oxygen third
Use of gases gained from fractional distillation of air
Nitrogen- fertilizers
Argon - lightbulbs
Oxygen - makes steel for welding
Greenhouse effect
When some of the thermal energy from the sun is absorbed by greenhouse gases and is re-emitted in all directions reducing the amount of energy lost into space as it is trapped within the earths atmosphere causing global warming
Effect of greenhouse gases
Suns thermal energy enters earths atmosphere where some is reflected back from earths surface but most is absorbed and re-emmited back from earth into space.
Some of the thermal energy from the sun is absorbed by greenhouse gases and re-emitted in all directions. (Greenhoiuse effect)
This reduces the amount of energy lost into space and traps it within the earths atmosphere causing global temperature to rise(Global Warming)
Air pollutants(6)
Carbon dioxide
Particulates
Oxides of nitrogen
Sulfur oxides
Methane
Carbon monoxide
Source of sulfur dioxide
Combustion of fossil fuels containing sulfur (at power stations)
Sulfur dioxide - Adverse effects and solutions
Exposure cuases respiratory problems
Forms acid rain when dissolved in water-corrodes buildings + reduces productivity of soil+increases acidity of lakes
Sulfur dioxide - solution to adverse effects
Using low sulfur fules and flue gas desulfurisation
Flue gas desulfurisation
Calcium oxide being added to neutralise sulfur dioxide
Carbon dioxide source (formula as well)
Complete combustion of carbon containing fuels such as methane
Adverse effects of carbon dioxide
Higher levels of carbon dioxide lead to increased global warming which lead to climate change
Source of carbon monoxide
Incomplete combustion of carbon containing fuels such as there being limited oxygen when petrol is being burned in a car cylinder
Adverse effects of carbon monoxide
Toxic as it combines with haemoglobin in blood and prevents it from carrying oxygen
Strategies to rdiuce effects of carbon monoxide
Catalytic converters in cars prevent carbon monoxide from forming
Source of particulates
Incomplete combustion of carbon containing fuels (fossil fuels) can produce particulates of carbon (soot)
Incomplete combustion of methane can cause carbon monoxide and carbon
Adverse effects of particulates
Respiratory problems and cancer
Sources of oxides of nitrogen NO, NO2 (2)
Formed in car engine cylinders when oxygen and nitrogen from the air react at high temperatures and in the atmosphere during lightning storms
Adverse effects of oxides of nitrogen
Repiratory problems - acute lung irritation and bronchitis
Gases form photochemical smog and acid rain when dissolved in water
Strategies to reduce effect of nitrogen oxides (equation as well)
Catalytic converters in cars reduce the amount of nitrogen oxides in the air
2CO + 2NO → 2CO2 + N2
Sources of methane (2)
Decomposition of vegetation
Waste gas from digestion in animals
Adverse effects of methane
Increased global warming which leads to climate change
How to reduce effects of climate change (4)
Planting trees
Reduction in lifestock farming
Decreasing the use of fossil fuels
Increasing the use of hydrogen and renewable energy such as wind and solar
How to reduce effects of acid rain (2)
Reducing emmisions of sulfur dioxide by using low sulfur fuels and flue desulfurisation with calcium oxide
Use of catalytic converters in vehichles
Catalysts used in catalytic converters and what they do
Platinum-rhodium alloy which removes pollutant gases from the exhaust by oxidising them and reducing them at 200*c
Equation for what happens to carbon monoxide and nitrogegn monoxide in a catalytic converter
CO is oxidied, NO is reduced
2NO + CO2 -> 2CO2 + N2
What happens to and equation for carbon monoxide in a catalytic converter
It is oxidised
2CO + O2 -> 2CO2
What happens to and equation for hydrocarbons in a catalytic converter
They are oxidised
C7H16 + 11O2 -> 7CO2 + 8H2O
Photosynthesis definition, word equation and symbol equation
Reaction between CO2 and H2O to produce oxygen and glucose in the presence of chlorophyl using energy from light
Carbon dioxide + water -> glucose + oxygen
6CO2 + 6H20 -> C6H12O6 + 6O2
Substances used for Chemical test for water
Copper(II) sulphate (CuSO4)
Cobalt(II) chloride paper (CoCl2)
Chemical test for water using anhydrous copper (II) sulphate
It is a reversible reaction, CuSO4 + H2O -> CuSO4.5H20
Colour change is due to the crystallisation of water as the water bonds to the copper atoms
Reaction from off-white to blue is exothermic
Chemical test for water using cobalt (II) chloride paper (CoCl2)
Turns from blue to pink in the presence of water
Hydrous copper chloride is formed
Forward reaction is exothermic as it requires bonds to form
Tests for pure water
Pure substances boil at specific, sharp temperatures. Pure water boils at 100ºC.
Impurities tend to increase the boiling point, so water that boils above 100ºC is impure
Impurities tend to decrease the melting point. Water that melts below 100ºC is impure
Distilled water
Water that has been heated to form a vapour and then condensed back to a liquid so that it contains very few impurities
Used in practical chemistry because of its hugh purity
Natural sources of water(3)
Lakes
Rivers
Underground water sources
3 ways water is used + examples of each
Home - drinking, cooking, cleaning, as a solvent, drinking
Agriculture - water for crops, drinking for animals
Industrial - solvent, hydroelectric power manufacture of chemicals
Beneficial substances found in water from natural sources(2)
Dissolved oxygen - for aquatic life
Metal compounds - provides essential minerals for life
Harmful substances in water from natural sources (4)
Metal compounds - toxic
Plastics - harm aquatic life
Nitrates + phosphates from fertilizers - lead to deoxigination of water and damage aquatic life
Sewage- contain harmful microbes which cause disease
Process of water treatment (11)
Water is pumped from source to reservoir
Water is aerated to separate iron compounds
Aluminium sulphate (Al2(SO4)3) is added to coagulate colloidal clay
Water is fed into sedimentation tank
Water passes through sand beds under pressure
Chlorine added to clear bacteria and algae (germicidal action)
Sulfur dioxide is added to remove excess chlorine
Water is neutralised using a lime slurry
Water is filtered through granulated activated carbon which improves the taste and smell by removing dissolved gasses
Fluoride added to prevent tooth decay
Water pumped to users
Germicidal action
Hydrochlorous acid penetrating cell walls by destroying the lipids and the internal structure
Commonly used as fertilizers
Ammonium salts and nitrates
What fertilizers contain and what they each promote
Nitrogen - makes chlorophyl and protein which promotes healthy leaves
Phosphorus - promotes healthy roots
Potassium - promotes growth and healthy fruit and flowers
What water soluble ions fertiliser compounds contain/sources
Ammonium ions (NH4+) and nitrate ions (NO3-) - source of soluble nitrate
Phosphate ions (PO4 -3) - source of soluble phosphorus
Most common potassium compounds dissolve in water to produce potassium ions (K+)
3 common fertilizer compounds
Ammonium nitrate (NH4NO3)
Ammonium phosphate ((NH4)3PO4)
Potassium sulphate (K2SO4)
How do you know which fertilizer would be most effective
The one with the most elements from nitrogen, phosphorus and pottassium
Use of sedimentation
To remove soluble solids
Why we use distilled water in a chemical lab instead of tap water
Because it contained fewer chemical impurities
How to test for purity of water
Freeze it then see if it melts at 0 degrees, and see if it boils at 100 degrees
