661. The yellow colour in photochemical smog is due to presence of__________________?
A. dinitrogen oxide
B. nitrogen dioxide
C. chlorine gas
D. chlorine dioxide

662. Which of the following is not primary pollutant__________________?
A. SO3
B. CO
C. NO
D. H2SO4

663. Which of the following gases is the main cause of acid rain ?
A. CO
B. NO2
C. both a & b
D. none of the above

664. Which of the following factors help to measure quallity of water ?
A. DO
B. BOD
C. COD
D. all of the above

665. A single chlorine free radical can destroy how many ozone molecules ?
A. 10
B. 100
C. 10000
D. 100000

666. Chlorination of water may be harmful if the water contains_________________?
A. Ammonia
B. Dissolved oxygen
C. Carbon dixide
D. All

667. Which of the following is used as water disinfectant to avoid the formation of toxic compounds_________________?
A. Cl2
B. O3
C. ClO2
D. both B & C

668. Ozone hole is substantial depletion of ozone in every year during__________________?
A. Aug – Nov
B. Sep – Nov
C. Nov – Dec
D. Dec – Jan

669. Which of the following solutions of H2SO4 is more concentrated ?
A. 1 Molar solution
B. 1 molal solution
C. 1 normal solution
D. all have same concentration

670. Which of the following is an example of liquid in gas solution?
A. Opals
B. Dust particles in smoke
C. Paints
D. Fog