Alum’s capacity to purify water is due to
1.softens hard water
2.pathogenic bacteria get destroyed
3. impurities’ coagulation
4. it improves taste
 The coldest region of the atmosphere
1.Troposphere
2.Thermosphere
3.Stratosphere
4.Mesosphere
Depletion of the ozone layer is caused due to
1.Ferrocene
2.Fullerenes
3. Freons
4.Polyhalogens
Find the incorrect statement
1. BOD value of clean water is less than 5 ppm
2. Drinking water pH should be between 5.5-9.5
3.carbon, sulphur and nitrogen oxides are the most widespread air pollutants
4.dissolved oxygen concentration below 5 ppm is ideal for the growth of fish
Find the secondary pollutant among these
1.PAN
2.N2O
3.SO2
4.CO2
In the air, N2Â and O2Â occur naturally but they do not react to form oxides of nitrogen because
1.oxides of nitrogen are unstable
2.catalyst is required for the reaction
3. the reaction is endothermic
4.N2Â and O2Â do not react with each other
 Photochemical smog normally does not contain
1. Chlorofluorocarbons
2.Peroxyacetyl nitrate
3. Ozone
4.Acrolein
The compound essential for the process of photosynthesis has this element
1. Ca
2.Ba
3. Fe
4.Mg
The reaction responsible for the radiant energy of the Sun is
1.nuclear fission
2.nuclear fusion
3. chemical reaction
4.combustion
Which of the oxide of nitrogen is not a common pollutant?
1. N2O5
2. N2O
3.NO
4.NO2