Environmental Chemistry Flashcards
Normal ph of rain water and how it is lowered
5.6
CO2 in atmosphere combines with H2O forming carbonic acid which dissociates weakly.
Gases causing acid rains
NO, NO2, SO2, SO3
Natural processes adding NO and NO2 to atmosphere
Lightning, volcanic eruptions, nitrifying bacteria, oxidation of ammonia
Artificial processes adding NO and NO2 to atmosphere
Burning fossil fuels
Natural processes adding SO2 and SO3 to atmosphere
Volcanic eruptions, Microbial activity taking place anaerobic conditions of the sediments of ocean beds and water bodies
Artificial processes adding SO2 and SO3 to atmosphere
Oxidation of S contained as impurities in diesel, oil used in crude oil refining and coal
Effects of the acidification of water
changes in behavioural patterns, retardation of organogeny and destruction of eggs and immature organisms of fish and other aquatic organisms
Death of coral polyps
Owing to the acidity, poisonous metal ions (Al3+, Cd2+, Cr2+, Hg2+) and other toxic ions strongly bound to the insoluble soil structure get detached and dissolve in water.
raises the hardness of water.
damage statues and other artistic creations made of calcium carbonate minerals such as marble
Measures that could be taken to reduce acid rains and acidification of water
(i) Burning coal with substances (CaCO3) that can react with sulphur dioxide (Fluidized bed combustion)
CaCO3(s)——-> CaO(s) + CO2(g)
CaO(s) + SO2(g)——> CaSO3(s)
(ii) Converting sulphur dioxide in power plant waste gases into solid substances. (reacting with calcium hydroxide (Lime slurry process))
Ca(OH)2(aq) + SO2(g)—–> CaSO3(s) + H2O (l)
Using coal and diesel with low sulphur content in coal and diesel power plants.
Greenhouse gases definition
gases which can absorb infrared radiations exist stably in the atmosphere for a long period of time are referred to as greenhouse gases.
Green house gases
H2O, CO2, CH4, N2O, CFC, HFC, HCFC
Processes adding methane
Disposal of urban wastes as heaps of garbage
Agricultural practices (paddy cultivation) undertaken in marshy and water-logged areas
Produced in the guts of the ruminants like cattle
Crude oil mining
Effects of global warming
Polar ice caps and glaciers in high mountains areas tend to melt while the oceanic waters expand.
Because of the high temperature epidemics (e.g; dengue, Ebola) spread fast.
Frequent emergence of hurricanes, tornadoes
Frequent long-standing droughts and flash floods
Measures to minimise global climatic changes
Limited the burning of fossil fuels, getting used to vegetarian diet, Minimizing deforestation, use renewable sources of energy such as ethanol and biodiesel
Mean wavelength of radio waves
1 cm
Mean wavelength of micro waves
1 mm
Mean wavelength of infrared waves
10 μm
Mean wavelength of visible waves
500 nm
Mean wavelength of UV waves
250 nm
Mean wavelength of X waves
1 nm
Divisions of the atmosphere and its major characteristics
Troposphere This stretches from the Earths surface to about 15 km upwards. A greater percent (about 99%) of the atmospheric gases is found in this region.Ascending from the Earth’s surface, the temperature decreases.
Stratosphere - The region from 15 km to 50 km from the Earth’s surface is stratosphere. The percentage of gases here is very low and ascending the layer, the temperature increases.
Thermosphere - It is the region above 50 km from the Earth’s surface. Amount of gases in this region is extremely small and the temperature is very high.
Ozone layer - A sub-zone in the stratosphere is referred to as the ozone layer. This extends from 20 km to about 35 km from the Earth’s surface. This is called ozone layer because most of the naturally occurring ozone gas in the Earth (around 95%) is found in this region.
Causes for ozone layer depletion
Sulphur containg compounds added to the upper atmosphere during powerful volcanic eruptions
- Chlorofluorocarbon
In addition to this, volatile organic compounds containing bromine (bromofluorocarbon) - Nitric oxide (NO) gas emitted by the aircrafts flying close to the upper atmosphere also depletes the ozone layer.
Industrial application of CFCs
- Used as the coolant gas in air conditioners and refrigerators
- Used as an aerosol spray under high pressure in perfumes
- Used as a blowing agent in the production of foam plastic
- Bromofluorocarbons are used in fire extinguishers.
How CFCs contribute to ozone layer depletion
CFCs are stable and highly volatile. They get evaporated and reaches to the stratosphere where it is exposed to UV radiation forming Cl free radicals. These free radicals react with ozone
Effects of ozone layer depletion
Skin cancer
Cataract in eyes
Mutations
Bleaching
Alternatives used at present for CFCs
Isobutane
hydrofluoroolefin
Requirements and chemical pollutants causing photochemical smog
NO, CH3(CH2)nCH3 (n = 1- 4)
sunlight and a temperature above 15 C
Main product formed during photochemical smog
O3
Adverse effects of the photochemical smog
Ozone is a toxic gas. When inhaled it causes respiratory complaints destruction of mucous membranes in the respiratory tract.
when plants are exposed to ozone yellow spots appear especially in tender leaves due to destruction of chlorophyll.
reducing the mechanical strength of rubber-based products.
Ozone bleaches colourings.
Least polluted form of water in the water cycle
Atmospheric water
pH of drinking water
6.5- 8.5
Eutrophication
The excessive growth of algae due to addition of nutrients to the water is defined as eutrophication.
Processes occurring during eutrophication
Due to the excessive growth of algae on the surface sunlight do not penetrate and reach the bottom surface which prevents photosynthesis from happening. Due to the production of H2S under anaerobic conditions area becomes foul smelling.
Major limiting factors for algal growth are phosphate ions and nitrate ions
If algal growth has to be stopped, PO4 3- level should be maintained at
0.05 ppm
Human activities causing eutrophication
agriculture
disposal of industrial waste
addition of domestic detergents
Heavy metals definition
metal whose density is greater than 5 g cm-3 or a metal whose relative density stands above 5
atomic number greater than 20.
cations which give insoluble precipitates with sulphide ions (S2-) and hydroxide ions (OH-)
Sources of heavy metals
Industrial emissions, mining waste, leaded gasoline, leaded paints, metal pipe welding materials
Effects of dissolved hydrocarbons
When they occur in water, they are decomposed by bacteria. This increases the oxygen demand of water and decreases the dissolved oxygen level (DO).
Disorders caused due to heavy metals
Brain damage, insomnia, kidney damage, minamata disease, Arsenicosis
PbCrO4 colour
yellow
Products of photochemical smog other than ozone
PAN (peroxyacetylnitrate)
PBN (peroxybencylnitrate)
voltile aldehydes
particle matter
How to identify CFC, HFC and HCFC
CFC contains 1 C atom and all other atoms are Cl and F
HFC contains 1/2 C atoms,1 H atom and all others are F
HCFC contains 1 C atom, 1 H atom and all others are Cl and F
Plastic cups are made up of
Polystyrene
Uses of bakelite
Used to make heat stable components of electrical circuits
