Question

A water sample has ppm level concentration of follwing anions $F^{-}=10;S{O}_3^{2-}=100;N{O}_3^{-}=50$ the anion/ anions that make \ makes the water smaple unsuitable for drinking is / are :

• A. only $N{O}_3^{-}$
• B. both $S{O}_4^{2-}$ and $N{O}_3^{-}$
• C. only $F^{-}$
• D. only $S{O}_4^{2-}$

Answer 1

The correct option is C only $F^{-}$

$N{O}_3^{-}$ ; The maximum limit of nitrate in drinking water is 50 ppm. Excess nirate in drinking water can cause disease. Such as methemoglobinemia.
$S{O}_4^{2-}$ ; above 500 ppm of $S{O}_4^{2-}$ ion in drinking water causes laxative effect otherwise at moderate levels it is harmless
$F^{-}$ ; Above 2 ppm concentration of $F^{-}$ in drinking water cause brown mottling of teeth.
$\therefore$ The concentration given in equstion of $S{O}^2{-}_4$ & $N{O}_3^{-}$ in water is suitable for drinking but the concentration of $F^{-}$ (i.e 10 ppm make water unsuitable for drinking purpose :