Which of the following gases contributes to the greenhouse effect?
A. Oxygen
B. Hydrogen
C. Nitrogen
D. Carbon dioxide
Answer: Option D
Solution (By JKSSB Mock Tests)
CO₂ is a major greenhouse gas that absorbs infrared radiation and re-emits it, warming the atmosphere. Other GHGs: CH₄, N₂O, water vapor, CFCs. N₂ and O₂ are diatomic homonuclear molecules that do not absorb IR and are not GHGs. Hydrogen is not a GHG. The increase in CO₂ due to human activities is driving climate change.
Explanation:
Permanent hardness (due to CaSO₄ etc.) can be removed by adding Na₂CO₃, which precipitates CaCO₃. Boiling only removes temporary hardness. Ion exchange and calgon also work.
Explanation:
Chlorination is the disinfection of water using chlorine or chlorine compounds to destroy pathogenic microorganisms. Chlorine reacts with water forming hypochlorous acid (HOCl) which is a strong germicide. Ozonation uses ozone; distillation involves boiling and condensation. Filtration removes particulate matter but not all microorganisms. Chlorination is cost-effective and provides residual protection, though it may produce trihalomethanes as by-products.
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