The reagent used in the determination of the chemical oxygen demand $(COD)$ of a water sample is

The $F^{-}$ ions make the enamel on teeth much harder by converting hydroxyapatite (the enamel on the surface of teeth) into much harder fluoroapatite having the formula.

Methane gas has a global warming potential approximately $25$ times that of which of the following gases?

Some reactions of $NO_2$ relevant to photochemical smog formation are:
$NO_{2(g)} \xrightarrow{hv} NO_{(g)} + X$
$X + O_2 \rightarrow Y$
$NO + Y \rightarrow NO_2 + A$
$O + O_2 + M \rightarrow B + M$
Identify $A, B, X$ and $Y$.

Which gaseous pollutant,even in low concentrations,causes respiratory distress such as inflammation and irritation in the human respiratory tract?

Photochemical smog is related to the pollution of