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A water sample contains the following anions at ppm concentrations: F− = 10, SO4²− = 100, and NO3− = 50. Which of these anion(s) make the sample unfit for drinking?

1. Only NO3−
2. Both SO4²− and NO3−
3. Only F−
4. Only SO4²−

Correct answer: Only F−

Solution

Fluoride (F−) at elevated levels can pose health risks, particularly to dental health, making the water sample unfit for drinking. While nitrate (NO3−) can also be harmful at high concentrations, the level of fluoride in this sample is specifically noted as a concern.

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