Question

A wastewater sample contains two nitrogen species, namely ammonia and nitrate. Consider the atomic weight of N, H, and O as 14 g/mol, 1 g/mol, and 16 g/mol, respectively. In this wastewater, the concentration of ammonia is 34 mg NH\(_3\)/liter and that of nitrate is 6.2 mg NO\(_3^-\)/liter. The total nitrogen concentration in this wastewater is \(\underline{\hspace{1cm}}\) milligrams nitrogen per liter. (round off to one decimal place)

Hint:

To find the total nitrogen concentration, convert each nitrogen species to its equivalent nitrogen content using their molecular weights.

Answer 1

Correct Answer: 29

% Solution To calculate the total nitrogen concentration, we need to convert the concentrations of ammonia and nitrate to their equivalent nitrogen concentrations. The molecular weights of ammonia (NH\(_3\)) and nitrate (NO\(_3^-\)) are 17 g/mol and 62 g/mol, respectively. - For ammonia (NH\(_3\)), the nitrogen content is \( \frac{14}{17} \). Therefore, the nitrogen concentration from ammonia is: \[ \text{Nitrogen from NH}_3 = 34 \times \frac{14}{17} = 28 \, \text{mg N/liter} \] - For nitrate (NO\(_3^-\)), the nitrogen content is \( \frac{14}{62} \). Therefore, the nitrogen concentration from nitrate is: \[ \text{Nitrogen from NO}_3^- = 6.2 \times \frac{14}{62} = 1.4 \, \text{mg N/liter} \] The total nitrogen concentration is the sum of the nitrogen concentrations from ammonia and nitrate: \[ \text{Total nitrogen} = 28 + 1.4 = 29.4 \, \text{mg N/liter} \] Thus, the total nitrogen concentration is \( \boxed{29.0 \, \text{mg N/liter}} \).