Envi Chem

Question 1

What is COD

Answer 1

Chemical oxygen demand
The amount of oxygen required to oxidise organic substances present in polluted water is called chemical. It is determined by oxidising organic matter with a mixture of K2CR202 and 50% of H2 SO4 solution. It is an important parameter for determining the quality of water.

Question 2

What is BOD?

Answer 2

biochemical oxygen demand
The amount of oxygen used by micro organisms present in water during five days at 20°C is called biochemical, oxygen demand. It is empirical in nature for pure water. BOD is about 1PPM

Question 3

Greenhouse gases

Answer 3

CO2, CH4, O3, CFC’s (chloro fluoro carbons ) and water vapour in atmosphere

Question 4

Which oxides cause acid rains what is its pH value?

Answer 4

Oxides of sulphur and oxides of nitrogen cause acid rain
The pH level of acid rain is 5.6

Question 5

Adverse effects of acid rain

Answer 5

Acid rains reduce the life of buildings and historical monuments
Acid rains decrease the fertility of soil by reducing the pH level of soil
As it rains decrease the productivity of fish in water
Acid rains decrease the quality of drinking water
Ammonium salts formed by acid rains can be seen as atmospheric haze

Question 6

Name the common components of photochemical smog

Answer 6

Ozone, nitric oxide, formaldehyde, PAN (peroxy acetyl nitrate), acrolein
Also called oxidising smog