Nitrate is a common contaminant coming from run off from fertilizer use, leaking from septic tanks and sewage; and erosion of natural deposits. The maximum contaminant level (MCL) of nitrate (measured as Nitrogen) is 10.0mg/L in drinking water. Express this MCLin terms of (a) ppm, (b) ppb, and (c) moles/m3.

A. 10 ppm

B. 10000 ppb

C. 0.714 mol/m3

Explanation:

A.

Parts Per Million is defined as 1 milligram mass of solute per 1 liter of solvent.

Nitrate concentration (as Nitrogen) = 10 mg/L

In ppm,

10 ppm.

B.

Converting Parts Per Million (ppm) to Parts Per Billion (ppb),

1 ppm is equal to 1000 ppb.

10 ppm = (1000*10) ppb

= 10000 ppb

C.

Molar mass of nitrogen = 14 g/mol

Molar concentration = mass concentration/molar mass

Mass concentration in g/m3,

1 liter = 0.001 m3

= 10 mg/l * 1l/0.001 m3

= 10000 mg/m3

mg to g,

1000 mg = 1 g

= 10000 mg/m3 * 1g/1000mg

= 10 g/m3

Molar concentration = 10/14

= 0.714 mol/m3