The maximum allowable amount of nitrate, measured as nitrogen, in drinking water is 10.0 ppm (by mass). Calculate the correponding molarity of the nitrate ion.

• A. 3.54×10⁻⁵ M NO₃⁻
• B. 7.14×10⁻³ M NO₃⁻
• C. 7.14×10⁻⁴ M NO₃⁻
• D. 4.68×10⁻⁴ M NO₃⁻

Answer: (C)