Which oxide of nitrogen is not a common pollutant introduced into the atmosphere both due to natural and human activity?

Which of the following is responsible for the greenhouse effect?

What is smog? How is classical smog different from photochemical smog?

$A$ water sample has $ppm$ level concentration of following anions: $F^{-} = 10 \ ppm$,$SO_4^{2-} = 100 \ ppm$,$NO_3^{-} = 50 \ ppm$. The anion/anions that make the water sample unsuitable for drinking is/are:

Which of the following causes damage to buildings containing calcium and is responsible for causing cough and throat congestion in humans?

Identify the reactions that occur in photochemical smog.
$(i)$ $CH_2=O + H_2 \longrightarrow CH_3OH$
$(ii)$ $NO_{2(g)} \xrightarrow{h \nu} NO_{(g)} + O_{(g)}$; $O_{(g)} + O_{2(g)} \longrightarrow O_{3(g)}$
$(iii)$ $CH_4 + 2O_3 \longrightarrow CH_2=O + 2H_2O$
$(iv)$ $NO_{(g)} + O_{3(g)} \longrightarrow NO_{2(g)} + O_{2(g)}$