Calculating Ion Concentration from pH

Calculating [Ion] from pH We use logarithms to do this N = 10x, then log N = x [H+] = 10-pH [H+] = invlog(-pH) [OH-] = invlog(-pOH) On the calculator press 2nd log-pH#

Calculations of [H+] or [OH-] Ex 1: What are [H+] and [OH-] in a healthy person’s blood that has a pH = 7.40 at temp 298 K? Kw = [H+] x [OH-] 1 x 10-14 = [3.98 x 10-8] x [OH-] 3.98 x 10-8 3.98 x 10-8 2.51 x 10 -7 = [OH-] [H+] = invlog(-pH) [H+] = invlog(-7.40) [H+] = 3.98 x 10-8

Calculations of [H+] or [OH-] Ex 2: What are [H+] and [OH-] at a pH = 2.3? Kw = [H+] x [OH-] 1 x 10-14 = [0.0050] x [OH-] 0.0050 0.0050 2.0 x 10 -12 = [OH-] [H+] = invlog(-pH) [H+] = invlog(-2.3) [H+] = 0.0050

Calculations of [H+] or [OH-] Ex 3: What are [H+] and [OH-] at a pH = 5.54? Kw = [H+] x [OH-] 1 x 10-14 = [2.88 x 10-6] x [OH-] 2.88 x 10-6 2.88 x 10-6 3.47 x 10 -9 = [OH-] [H+] = invlog(-pH) [H+] = invlog(-5.54) [H+] = 2.88 x 10-6