University:
Loyola University Maryland
Course:
CH 101 | General Chemistry I
Academic year:

2024
Views:

221

Pages:

2
Author:

Natasya J.

The pH Concept A more concise way to express the acidity or basicity of any aqueous solution. Important to know [H+] of any aqueous system, organic, inorganic, or biochemical. Acidic solutions are defined as [H+] > [OH-] or [H+] > 10^-7 M Basic solutions are defined as [H+] < [OH-] or [OH-] > 10^-7 M Neutral solutions are defined as [H+] = [OH-] = 10^-7 M. pH is a concise term, devised by Arrhenius, to express [H+] without units or exponents pH = -log[H+] Why log? Why negative log? Wide range of [H+] values possible. pH easy to calculate from simple exponential [H+] values as 10^-1 M, 10^-12 M, 10^-7 M, 10^0 M, 10^-9 M, etc. resulting range of possible pH values. Use a calculator for terms with significant parts other than one. (Dissection of negative log terms) How are sig. figs. handled in common log problems? Exs: [H+] = 6 x 10^-9 M, pH = 8.2 [H+] = 3.7 x 10^-11 M, pH = 10.43 pH = 9.7, [H+] = 2 x 10^-10 M pH = 2.90, [H+] = 1.3 x 10^-3 M Alternative, but rarely used, pOH = -log[OH-] Since [H+] · [OH-] = 10^-14, then pH + pOH = 14 Exs: pOH = 12.60 pH = 1.40, [H+] = 4.0 x 10^-2 M, [OH-] = 2.5 x 10^-13 M [OH-] = 2.5 x 10^-9 M, [H+] = 4.0 x 10^-6 M Exs of specific solutions: What are the [H+], pH, pOH, and [OH-] of a 0.0023 M HCl solution? [H+] = 0.0023 M, pH = 2.64, pOH = 11.36, [OH-] = 4.3 x 10^-12 What are the [H+], pH, pOH and [OH-] of a 0.00065 M Ba(OH)2 solution? [OH-] = 1.3 x 10^-3 M, pOH = 2.89, pH = 11.11, [H+] = 7.8 x 10^-12 M