Question

In clinical applications, the unit parts per million (ppm) is used to express very small concentrations of solute, where 1 ppm is equivalent to 1 mg of solute per 1 L of solution. Calculate the concentration in parts per million for each of the following solutions.

a) There are 39 μg of calcium in a total volume of 83 mL.​

b) There is 0.85 mg of caffeine in a total volume of 149 mL.​

c) There is 0.51 mg of trace particles in a total volume of 63 dL solution.​

Answer 1

Solution

a)

Convert amount of calcium from µg to mg

amount of calcium = 39µg

= 39 x 10^-6 g

= 39 x 10^-6 x 10³ mg

= 3.9 x 10^-2 mg
Convert volume from mL to L

volume = 83 mL

= 83 x 10^-3 L

= 8.3 10^-2 L

Thus concentration = (3.9 x 10^-2 mg)/ (8.3 10^-2 L)

= 0.50 mg/L

= 0.50 ppm

b)

amount of caffeine = 0.85 mg
Convert volume from mL to L

volume = 149 mL

= 149 x 10^-3 L

= 0.149 L

Thus concentration = (0.85 mg)/ (0.149 L)

= 5.7 mg/L

= 5.7 ppm

c)

amount of caffeine = 0.51 mg
Convert volume from dL to L

volume = 63 dL = 6.3 L (since 1 dL = 0.1 L)

Thus concentration = (0.51 mg)/ (6.3 L)

= 0.0809 mg/L

= 0.081 ppm