Questions - Answers
2 Marks Questions.
1. What is green Chemistry?
A: A new branch of chemistry helps in reduction in the production & use of harmful pollutant by using existing knowledge of Chemistry and other sciences.
e.g.: Using H2O2 instead of Cl2 for bleaching paper.
2. What is global warming (green house effect)?
A: Increased concentration of the gases like CO2, CH4, NO, N2O in atmosphere, absorption of infrared radiation (of sun rays) takes place and the temperature of the earth increases.
3. Write any two effects of global warming?
A: * The decrease in ground water level
* Increase in sea level due to melting of polar ice caps.
4. What are the causes of acid rains?
A: Oxides of Nitrogen (NO, NO2) and sulphur (SO2) released from industries and automobiles react with oxygen and dissolve in rain water to form HNO3, H2SO4 and Comedown to earth as acid rains.
5. Acid rains are harmful. Why?
A: * As they decrease in fertility of soil.
* As they reduce the life of buildings and damage of historical monuments like Taj Mahal.
6. Define COD & BOD.?
A: Chemical Oxygen Demand (C.O.D.): The amount of Oxygen required to Oxidise organic substances present in polluted water.
Bio Chemical Oxygen Demand (B.O.D.): The amount of oxygen consumed by micro organisms present in polluted water during 5 days at 20°C.
7. Define pollutant & contaminant.
A: Pollutant: A substance which is already present in nature and its concentration increases in the environment due to natural or human activity and adversely effects the environment. e.g.: SO2, CO2.
Contaminant: A substance which is not present in nature, enters newly into environment and adversely effects the environment
e.g.: MIC, DDT, BHC.
8. Define Receptor & Sink.
A: Receptor: The medium which is badly effected by the pollutant.
e.g.: eyes are receptor during traffic jam.
Sink: The medium which is not only effected by the pollutant but also remains there.
e.g.: Sea water, trees are big sinks for CO2.
9. How are Fluorides removed by Nalgonda technique?
A: Nalgonda technique: This harmless, cheap method is developed by National Environmental Engineering and Research Institute, Nagpur in Nalgonda. In this method fluorides are removed by adding required quantities of bleaching powder, lime, alum and the water is kept for some time. Fluoride ions are removed as Calcium aluminium fluoride complex.
10. What is the effect of CO on human beings?
A: CO has great affinity towards haemoglobin of blood and forms a stable complex carboxy haemoglobin. (CO + Hb → COHb). Which causes loss of vision, Headache, Unconsciousness.
11. What is T.L.V.?
A: Threshold Limit Value (T.L.V.): The permissible level of a toxic pollutant in atmosphere where a healthy person works in that atmosphere for 8 hours per day without any adverse affect. e.g.: TLV for Zn = 1mg/m3.
12. What are 'Bioamplification' and 'Eutrophication'?
A: Bio amplification: The process of increase of concentration of poisonous pollutant from lower animal to higher animal through food chain.
Eutrophication: Drying of a lake due to overgrowth & decay of algae due to over nutrition in water of a lake.
13. What Happens when holes are formed in ozone layer present in stratosphere?
A: * Causes skin cancer & cataract
* Decreases the efficiency of photosynthesis in plants.
14. What are CFCs? They are boon to industry but a curse to the environment. Why?
A: Artificial compounds containing Cl, F, C is known as CFC (or freon). They are cheap and widely used (e.g. CFCl3, CF2Cl2). But they are responsible for ozone depletion.
15. What happens if fluorides are present in water? How is it detected?
A: When the concentration of fluorides in drinking water exceeds 3 ppm, causes "Fluorosis" disease (teeth turns yellow, bones become weak) due to formation of Ca F2
(Ca + F2→ CaF2)
Fluorides are detected by using zirconium alizarin - s dye (coloured substance). When this dye is added to water contains fluorides, the colour of the dye fades with the increase in the concentration of fluoride ions.
