The pH of several solutions was measured in a hospital laboratory; convert each of the following pH values into the molar concentration of H 3 O ions: (a) 4.8 (the pH of a urine sample); (b) 0.7 (the pH of a sample of fluid extracted from a stomach); (c) 7.4 (the pH of blood); (d) 8.1 (the pH of exocrine pancreatic secretions)

(a) 1.6 x 10⁻⁵ M

(b) 0.20 M

(c) 4.0x 10⁻⁸ M

(d) 7.9 x 10⁻⁹ M

Explanation:

The pH value is the negative logarith of the concentration of hydronium ions in solution:

pH = - log[H₃O⁺]

so to convert the given pHs in this question to molar concentration of H₃O⁺, we need to take the inverse logarhitmic function of minus pH.

(a) pH (urine) = 4.8

inverse log ( - 4.8) = 10^ (-4.8) = 1.6 x 10⁻⁵

[H₃O⁺] urine = 1.6 x 10⁻⁵ M

(b) pH (stomach fluid) = 0.7 M

inverse log (-0.7) = 10^ (-0.7) = 0.20

[H₃O⁺] stomach fluid = 0.20 M

(c) pH (blood) = 7.4

inverse log (-7.4) = 10^ (-7.4) = 4.0x 10⁻⁸

[H₃O⁺] blood = 4.0x 10⁻⁸ M

(d) pH (pancreatic) = 8.1

inverse log (-8.1) = 10^ (-8.1) = 7.5 x 10⁻⁹

[H₃O⁺] pancreatic = 7.9 x 10⁻⁹ M