The greenhouse effect is because of the 
Green house gases such as CO2, ozone, methane, the chlorofluoro carbon compounds and water vapour form a thick cover around the earth which prevents the IR rays emitted by the earth to escape. It gradually leads to increase in temperature of atmosphere.
Which of the following is/are the hazardous pollutant(s) present in automobile exhaust gases? (i)N2 (ii) CO (iii) CH4 (iv) Oxides of nitrogen
CO and oxides of Nitr ogen ar e poisnous gases present in automobile exhaust gases.
Green chemistry means such reactions which :
Green chemistry may be defined as the programme of developing new chemical products and chemical processes or making improvements in the already existing compounds and processes so as to make less harmful to human health and environment. This means the same as to reduce the use and production of hazardous chemicals. i.e. correct answer is option (b).
Which one of the following statement is not true ?
The ideal value of D.O for growth of fishes is 8 mg/ℓ . 7mgℓ is desirable range, below this value fishes get susceptible to desease. A value of 2 mg/ℓ or below is lethal for fishes.
Which one of the following statements regarding photochemical smog is not correct? 
The oxidised hydrocarbons and ozone in presence of humidity cause photochemical smog.
Hydrocarbons + O2, NO2, NO, O, O3 → Peroxides, formaldehyde, peroxyacetylnitrate (PAN), acrolein etc.
It is oxidising in nature and causes irritation to eyes, lungs, nose, asthamatic attack and damage plants.
Roasting of sulphides gives the gas X as a by product. This is colorless gas with choking smell of burnt sulphur and caused great damage to respiratory organs as a result of acid rain. Its aqueous solution is acidic, acts as a reducing agent and its acid has never been isolated. The gas X is : [NEET 2013]
Based on the features given above the gas must be SO2
Which one of the following statements is not true? [NEET Kar. 2013]
Acid rain is the rain water containing sulphuric acid and nitric acid which are formed from the oxides of sulphur and nitrogen present in the air as pollutants and rain water has a pH of 4-5.