The concentrations of pollutants are often reported as parts per million (ppm).

Question

The concentrations of pollutants are often reported as parts per million (ppm). Parts per million of a solution is defined as: ppm = mass of solute/mass of solution X 1E+6

The U.S. Environmental Protection Agency (EPA) limit for barium in municipal drinking water is 2 ppm.

(a) Calculate the maximum mass percentage of barium allowed in drinking water. (%)

(b) Calculate the molarity of a solution of barium that is 2 ppm. Assume that the density of the solution is 1.00 g/mL. (M)

(c) Express the concentration of barium as mg per liter. (mg/L)

Explanation / Answer

given 2ppm

so accroding to the given formula

mass of solute /mass of solution = 2 x 10-6

a)   ppm = ( mass of solute / mass of solution ) x 10^6

ppm x 10-4 = ( mass of solute / mass of solution ) x 100

ppm x 10-4= masss %

so

mass % = 2 x 10-4

the maximum mass percentage is 2 x 10-4

b)

molarity = moles of solute x 1000 / volume of solution (ml)

= ( mass of solute / molar mass of solute ) x 1000 / ( mass of solution / density of solution )

= mass of solute x 1000 x density of solution / molar mass of solute x mass of solution

= ( mass of solute / mass of solution ) x 1000 x density of solution / molar massof solute

= 2 x 10-6 x 1000 x 1 / 137.3

=1.456 x 10-5

so the molarity = 1.456 x 10-5 M

c)

conc in g/L = molarity x molar mass

conc in g/L = 1.456 x 10-5 x 137.3

conc in g/L= 2 x 10-3

conc in mg/L = 2 mg/L

so

conc in mg/L = 2

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