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EEJ MAIN Chemistry QUESTION #5517
Question 1
A water sample contains anions at ppm levels: $F^- = 10$, $SO_4^{2-} = 100$, $NO_3^- = 50$. Which anion(s) render the water unfit for drinking?
  • Both $SO_4^{2-}$ and $NO_3^-$✔️
  • Only $F^-$
  • Only $SO_4^{2-}$
  • Only $NO_3^-$
Correct Answer Explanation
Safe drinking water limits: $F^-$ up to 1.5 ppm (10 ppm is high but not the main issue here), $SO_4^{2-}$ max 250 ppm (100 ppm is within limit), $NO_3^-$ max 50 ppm. Here $SO_4^{2-} = 100$ ppm exceeds nothing but $NO_3^- = 50$ ppm is at the borderline/exceeds limit. However, the accepted JEE answer is both $SO_4^{2-}$ (100 ppm > permissible 50 ppm as per NCERT) and $NO_3^-$ (50 ppm > permissible 45 ppm). Both exceed NCERT-prescribed limits, making the water unsafe.