Environmental Chemistry — Short Questions

Environmental chemistry is a part of environmental education. The objective of which is to enlighten the people particularly the students, about the importance of protection and conservation of our environment.

Increasing use of fossil fuels (natural gas, coal and petroleum) have polluted the atmosphere upto such an extent that it is difficult to breathe air in some areas of metropolitan cities.

Burning of fossils fuels (oil, natural gas, coal). Volcanic eruption, decomposition of vegetation, rapid growth of populations urbanization, industrialization and transportation are the main factors to release particulate matter in atmosphere.

CO is poisonous gas because it bind to heamoglobin in blood. It hinders the supply of O2 in all parts of body and ultimately causes suffocation and death of or organism.

Acid rain can damage vegetation and plants. Many plants cannot live or grow in acidic soil. Tree roots hold the soil together on hills and mountain areas. If the trees are destroyed then the soil is washed way and new plants cannot grow there.

When Sulphur containing fossils fuels are burnt oxides of Sulphur (SOx), SO2, SO3 are produced.

SO2 irritates the eyes and causes breathing difficulties and acid rain.

S(s) + O2(g) → SO2(aq)
2SO2(aq) + O2(g) → 2SO3(aq)
SO2(aq) + H2O(g) → H2SO4(aq)

Methane(CH4), carbon dioxide (CO2) and Nitrous oxide (N2O) and water vapors produced due to burning of fossils fuels.

Geothermal energy is useful for us because it provides a renewable and sustainable source of energy. It can be used for electricity generation, heating buildings and supplying hot water. It is environmental friendly.

The process used to separate gases present in air is fractional distillation. In this process first air is cooled to liquefry it and then it is slowly warmed to boil gases at their boiling temperatures. Vapors of each gas are collected separately.

CO2 gas is released when carbonated drinks are opened.

Air pollutant like ozone, SO2, NO2, etc inhibits the growth of plants by reducing the amount of carbon dioxide absorbed during photosynthesis and reduce crops yield.

Sulphuric acid (H2SO4) and nitric acid (HNO3) are made when SO2 and NO2 dissolve in rain respectively.

NO2(aq) + H2O(g) → HNO3(aq)
SO2(aq) + H2O(g) → H2SO4(aq)

Tree roots hold the soil together on hills and mountain areas. If the trees are destroyed, then the soil is washed away and new plants cannot grow there.

Living things like Humans and animals inhale O2 from the air and exhale CO2 in to the air during respiration.

White plants consume CO2 from the air during photosynthesis

In this way living things add and plants remove CO2 from the air.

Rice plants produce oxygen as a by product of photosynthesis and methane (CH4) throw methaoeogenesis.

Methane gas (CH4) is produced during rotting of garbage.

Atmosphere is the envelope of different gases around the Earth.

The branch of chemistry which deals with the study of chemicals and other pollutants in the environment is called environmental chemistry.

Environmental science helps us to understand the complex interaction that occur in our ecosystem and the impacts on human life

Atmosphere Atmosphere is the envelope of different gases around the Earth.

Environment Environment is the sum of all social, biological, physical and chemical factors which constitutes the surroundings of living things.

Composition of dry air

Major Constituent | Percentage | Minor Constituent | Percentage
Nitrogen | 78.0 | Carbon dioxide | 0.03
Oxygen | 21.0 | Noble gases | About 1.0
| | Water Vapours | Variable

Pollutants are those substances which cause pollution while contaminants are those substances that make something impure.

Any substance (solid, liquid, or gas) in the air which has adverse effect on human health, quality of life and natural functioning of ecosystem is called an air pollutant.

It has two types, primary pollutants and secondary pollutants.

Naturally sulphur compounds are emitted in bacterial decay of organic matter, in volcanic gases and forest fires.

In open air burning produces CO2 gas which becomes part of atmosphere. CO2 is not a poisonous gas. Whereas in closed places CO is produced due to limited supply of oxygen. CO is poisonous gas and can be fatal. That's why burning in open air is preferred.

CO is poisonous gas. Being colourless and odourless its presence can be noticed easily and readily. It binds with haemoglobin. So, supply of oxygen is cut off. If inhaled for a longer time, it causes breathing difficulty which leads to death.

Sources of CO and CO2 Emission:

i. Both of these gases are emitted due to volcanic eruption and decomposition of organic matter naturally.

ii. The major source for the emission of these gases is combustion of fossil fuels (coal, petroleum and natural gas). Fossil fuels burnt in combustion engine of any type of automobile, kiln of any industry, or open air fires emit CO2 and CO.

Physical properties NO is colourless, odourless gas soluble in water. NO2 is reddish brown gas with pungent odour soluble in water Both are highly toxic gases.

Sources Exhaust fumes of motor vehicles, power stations and industries using fossil fuels.

Harmful effects Cough, headaches lung diseases, acid rain and greenhouse effect (global warming).

There is a giant floating patch of garbage spread over the Pacific Ocean. It contains about 100 million tons of garbage.

Acid rain means presence of excessive acids in rain water. This rain is produced when normal rain water dissolves oxides of sulphur and nitrogen in air. Rain water converts SO2 into H2SO4 and NOx to HNO3 and HNO3. These acids reduce the pH of rain water upto 4. Thus acid rain is formed on dissolving acidic air pollutants such as SO2 and NO2 in rain water.

Acid rain on soil and rocks leaches heavy metals (Al, Hg, Pb, Cr, etc.) with it and discharges these metals into rivers and lakes. Aquatic life present in lakes suffers because of high concentration of these metals. Especially high concentration of aluminium metal clogs the fish gills. It causes suffocation and ultimately death of fish.

Acid rain directly damages the leaves of trees and plants, thus limiting their growth. Depending upon the severity of the damage, plants growth can be hampered. Plants ability to bear cold or diseases reduces and they ultimately die.

Acid rain mitigation

a) Emission control: Measures to reduce emissions of sulfur dioxide, nitrogen oxides from industrial units, power plants, and vehicles are important for reducing acid rain. This can be achieved through the introduction of anti-pollution technologies and the use of cleaner fuels.

b) Low sulphur fuels: Promoting low sulphur fuels can also minimize the amount of sulphuric acid in the atmosphere that causes acid rain.

CO2 and water vapours maintain temperature of atmosphere. These gases absorb much of infrared radiations coming from Earth surface and warm the atmosphere.

CO2 is greenhouse gas. In atmosphere it acts like a glass wall of greenhouse. It absorbs infrared radiations and allows visible light to pass through. So, it absorbs most of outgoing radiations which result in heating of atmosphere. This is called Greenhouse effect.

CO2 layer acts like an envelope around the earth. It absorbs infrared radiations emitted by the Earths' surface and helps to keep it warm at night. Increased concentration of CO2 increases the average temperature of the earth surface gradually. This is called greenhouse effect.

Global warming is rising of temperature because of trapping of heat energy by carbon dioxide gas in the atmosphere.

Increasing in the temperature of the earth due to Global warming melts glaciers and snow caps that are increasing flood risk.

Greenhouse effect, depletion of ozone and acid rain are the global effect of pollution.

Due to burning of the large amount of coal, oil and natural gas, the amount of greenhouse gases, carbon dioxide together with other gases in the atmosphere has increased for the last 300 years. About half of this carbon dioxide is utilized by plant life during photosynthesis. As human being cut down forests, the capacity of the trees to remove CO2 from the air is diminished. Methane is another greenhouse gas which causes adverse effects. The increase in its concentration in air is due to the increased decay of vegetation matter, digestion in animals and increased farming of the rice fields.

Water vapours also act as greenhouse gas. When released into the atmosphere, water soon comes back to earth as acid rain.

Catalytic converters are used in the exhaust system of modern-day automobiles to reduce the emissions from an internal combustion engine. Due to non-availability of enough oxygen the carbon fuel in engine does not burn completely into carbon dioxide and water. Thus, toxic byproducts like CO and hydrocarbons are produced.

Advantages

A three-way catalytic inverter performed the following three functions simultaneously:

i. It reduces nitrogen oxide into elemental nitrogen and oxygen.
NOx(g) → N2(g) + O2(g)

ii. It oxidizes CO to CO2
2CO(g) + O2(g) → 2CO2(g) + O2(g)

iii. It oxidizes hydrocarbons into CO2 and H2O
CxH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

The emission of sulphur dioxide can be decreased either by using fuels which have significantly less sulphur contents or using flue gas desulphurization process. This process can remove sulphur dioxide gas from the exhaust gases of fossil fuel. Flue gas is the emitted material produced when fossil fuels are burnt in power plants. The desulphurization process involves the addition of absorbents like calcium oxide which can remove upto 95% of the sulphur dioxide from the flue gas.

Renewable resources are those resources than cat continue to exist despite being consumed over a period of time even as they are used.

These resources include Sun, wind, water, geothermal, biomass and hydrogen gas, generating electricity without damaging the environment.

Excessive pesticide and insecticide use harms birds through direct poisoning food chain contamination, habitat disruption and reproductive issues.

The carbon dioxide which is not utilized in photosynthesis goes on accumulating in the lower areas of the atmosphere and forms a thick dense layer. This layer behaves like glass sheet of greenhouse that allows the incoming solar radiation but does not allow it to escape outside, as a result of this the average temperature of the Earth rises.

Greenhouse gases absorb and emit infrared radiation due to their structure and vibrational properties. Other pollutant does not have such characters thats why they are not termed as greenhouse gases.

Catalytic converters are used in the exhaust system of modern-day automobiles to reduce the emissions from an internal combustion engine. Due to non-availability of enough oxygen the carbon fuel in engine does not burn completely into carbon dioxide and water. Thus, toxic by-products like CO and hydrocarbons are produced.

It oxidizes CO to CO2
2CO(g) + O2(g) → 2CO2(g)

Solar energy can be helpful for us in electricity generation, solar water heating and solar drying and agriculture application.