21.

Water is considered to be polluted if the dissolved oxygen D.O. content is less than ....  ppm

• 5

• 10

• 15

• 100

Identify the correct decreasing order of the following with respect to altitude from atmosphere

I. Troposphere

II. Mesosphere

III. Thermosphere

• II, III, I

• III, II, I

• I, II, III

• I, III, II

Which of the following is not an air pollutant?

• N₂

• N₂O

• NO

• CO

CFCl₃ is responsible for the decomposition of ozone to oxygen. Which of the following reacts with ozone to form oxygen ?

• Cl₂

• Cl^-

• F^-

• Cl^*

At T (K), 100 L of dry oxygen is present in a sealed container. It is subjected to silent electric discharge, till the volumes of oxygen and ozone become equal. What is the volume (in litres) of ozone formed at T (K) ?

• 50

• 60

• 30

• 40

Bhopal gas tragedy of 1984 was caused by

• carbon monoxide

• phosgene

• methyl cyanate

• methyl isocyanate

Among the following compounds, which one is not responsible for depletion of ozone layer?

• CH₄

• CFCl₃

• NO

• Cl₂

The chemical entities present in thermosphere of the atmosphere are

• O${}_2^{+}$, O⁺, NO⁺

• O₃

• N₂, O₂, CO₂, H₂O

• O₃, O${}_2^{+}$, O₂

The acceptable level of carbon monoxide gas (CO) in the atmosphere in ppm level is

• 9

• 250

• 49

• 850

Which air pollutant is responsible for Bhopal gas tragedy?

• PIC

• CFC

• MIC

• CO