These MP Board Class 11th Chemistry Notes for Chapter 14 Environmental Chemistry help students to get a brief overview of all the concepts.
MP Board Class 11th Chemistry Notes Chapter 14 Environmental Chemistry
→ Substances produced by natural causes or by human activities which cause harmful effect on the environment are called pollutant.
→ Such substances which when present in the environment pollute it, they are called contaminant.
→ Air pollutants are maximum in Troposphere.
→ Ozone layer situated in stratosphere prevent us from ultraviolet rays.
→ Oxides of nitrogen and sulphur cause acid rain.
→ CFC is the main cause of depletion of ozone layer.
→ The heat radiations (IR rays) coming from the sun are reflected from the earth’s surface and absorbed by gases like CO2. This increases the temperature and is called green house effect.
→ Along with CO2 CFC also cause green house effect.
→ 111 effect of green house effect is Globa! warming.
→ Pollutants are of two types :
- Degradable pollutants : Pollutants which can easily break down by micro-organisms. Example : Discarded vegetables, cow dung.
- Non-degradable pollutants : Pollutants which do not break down by micro-organisms. Example : DDT, plastic, heavy metals, chemicals etc.
→ Tropospheric pollution : It occurs due to presence of undesirable solid or gaseous particles in air. Gaseous air pollutants are oxides of S, N and C, H2S, hydrocarbons, ozone and other oxidants. Particulate pollutants are dust, mist, fumes, smoke, smog etc.
→ Vaporized material formed by minute carbon particles, obtained by combustion of a substance is called smoke.
→ Thin layer of fog, smoke and dust is called Smog. It is harmful mixture of smoke and fog.
→ Smog is of two types : (i) Classical smog, (ii) Photochemical smog.
→ Fine solid particles present in air whose size range from 01 µ to 25 µ are called dust.
→ In Green house system allow low wavelength solar radiation to enter but does not allow higher wavelength infrared radiations to go out.
→ Main green house gases are CO2, CH4, N2O and CFCs.
→ Main components of Acid rain are H2SO4 and HNO3. When pH of acid rain becomes less than 5-6, it is known as Acid rain.
→ Main source of soil pollution are : Detergent, poisonous metals, insecticides, acid, base, salt, insects, pharmaceutical waste.
→ Bio-chemical oxygen demand (BOD). Amount of oxygen required by bacteria to break down the organic matter (at 206° for 5 days) present in a certain volume of water sample is called B.O.D.
BOD = \(\frac{\text { Number of milligrams of } \mathrm{O}_{2} \text { required }}{\text { Volume of sample (in litres) }}=\frac{\text { Parts of } \mathrm{O}_{2}}{\text { Million part of sample }}\)
BOD for clean water is less than 5 ppm, whereas BOD of highly polluted water is 17 ppm or can be more than this.
→ Eutrophication : The process in which nutrient enriched water bodies support a dense plant population which kills animal life by depriving it of oxygen and results in subsequent loss of biodiversity is known as Eutrophication.
→ Green chemistry: It is a way of utilizing the existing knowledge and principles of chemistry to reduce the adverse production of pollutants.