A particular sample of air is 2.5% water vapor express the concentration of water vapor in parts per million

A. 0.0000025 ppm

B. 250 ppm

C. 25000 ppm

D. 0.025 ppm

25000 ppm

Explanation:

Parts Per Million is defined as the number of parts of a solute per one million parts of a solution.

ppm = (Weight of Solute / Weight of Solution) * 10⁶ - - - (1)

Let us suppose that the air (solution) weights 100 grams, then 2.5 % of water vapors will have following mass,

Mass of Vapors g / 100 g * 100 = 2.5

Or,

Mass of Vapors = 2.5 * 100 / 100

Mass of Vapors = 2.5 g

Hence, mass of water vapors is 2.5 g.

Now, putting mass of water vapors and air in eq. 1,

ppm = (2.5 / 100) * 10⁶

ppm = 25000