6
MCQ (Single Correct Answer)
Sewage containing organic waste should not be disposed in water bodies because it causes major water pollution. Fishes in such a polluted water die because of
A
large number of mosquitoes
B
increase in the amount of dissolved oxygen
C
decrease in the amount of dissolved oxygen in water
D
clogging of gills by mud
7
MCQ (Single Correct Answer)
Which of the following statements about photochemical smog is wrong?
A
It has high concentration of oxidising agents
B
It has low concentration of oxidising agent
C
It can be controlled by controlling the release of $\mathrm{NO}_2$, hydrocarbons, ozone etc
D
Plantation of some plants like pinus helps in controlling photochemical smog
8
MCQ (Single Correct Answer)
The gaseous envelope around the earth is known as atmosphere. The lowest layer of this is extended upto 10 km from sea level, this layer is
A
stratosphere
B
troposphere
C
mesosphere
D
hydrosphere
9
MCQ (Single Correct Answer)
Dinitrogen and dioxygen are main constituents of air but these do not react with each other to form oxides of nitrogen because ......... .
A
the reaction is endothermic and requires very high temperature
B
the reaction can be initiated only in presence of a catalyst
C
oxides of nitrogen are unstable
D
$\mathrm{N}_2$ and $\mathrm{O}_2$ are unreactive
10
MCQ (Single Correct Answer)
The pollutants which come directly in the air from sources are called primary pollutants. Primary pollutants are sometimes converted into secondary pollutants. Which of the following belongs to secondary air pollutants?
A
CO
B
Hydrocarbon
C
Peroxyacetyl nitrate
D
NO