Discussion Forum



1)

A water sample has ppm level concentration of following  anions $F^{-} =10 $:  $SO_{4}^{2-} =100 $ :  $NO_{3}^{-}=50$ the anion /anions that, make/makes the water sample unsuitable for drinking is/are


A) Only $NO_{3}^{-}$

B) Both $SO_{4}^{2-} and NO_{3}^{-}$

C) only $F^{-} $

D) Only $SO_{4}^{2-} $

Answer:

Option C

Explanation:

$NO_{3}^{-}$  The maximum limit of nitrate (NO3-) in drinking water is 50 ppm and its source is fertilizers. If the maximum limit is increased in water, it will cause methemoglobinemia (blue baby syndrome)

$SO_{4}^{2-} $   The maximum limit of sulphate ($SO_{4}^{2-} $) according to WHO is 500ppm and its source is acid rain, industries. Excess $SO_{4}^{2-} $ has laxative effect.

 $F^{-} $   The maximum limit of fluoride ( $F^{-} $)is about 1.5 ppm its highest concentration converts enamel to more hardest fluorapatite.  Concentration (>2 ppm) causes brown mottling of teeth and high concentration (>10ppm) is harmful to bones and teeth.

$\therefore$    $SO_{4}^{2-} $ (100 ppm) and  $NO_{3}^{-}$ (50 ppm) in water is suitable for drinking but the concentration of $F^{-} $ (10 ppm)makes water unsuitable for drinking.