The pH Scale
Unit 16.3
Chapter 15 Section 3
Pg. 559 - 567
Review: pH Scale
◦ a measure of how
acidic or basic a
substance is.
◦ Specifically, a measure of
the concentration of H+
Molar Concentration
◦ [ ] = concentration
◦ Ex. [H+] = concentration
of H+ in a solution.
◦ Concentration is
measured in Molarity
◦ Molarity =
𝑚𝑜𝑙𝑒𝑠
𝑣𝑜𝑙𝑢𝑚𝑒 (𝐿)
Determining [Ion]
◦ In any solution (acidic, basic, or neutral):
◦ [H+]∙[OH-] = 1 x 10-14
◦ Therefore, if you know the concentration of either
[H+] or [OH-] you can determine the other.
Determining Concentrations
◦ Calculate the [H+] of a solution if the [OH-] was
.005M.
Practice
◦ Calculate the [OH-] in a solution of 1.75 x 10-4 M HBr.
◦ HBr(aq)
H+(aq) + Br -(aq)
Calculating pH
◦ Formula: pH = - log [H+]
◦ Ex. What is the pH of 0.0010 M solution of HCl?
◦ [H+]= 0.0010 M
Practice
◦ Calculate the pH of a 3.00 x 10 -6 M solution of
HClO4
Calculating pH from [OH-]
◦ 1. Use [H+]∙ [OH−]= 1x10-14 to find [H+]
◦ 2. Plug [H+] in to pH = - log [H+]
◦ Ex. Calculate the pH of a 1.5 x 10 -3 M solution of NaOH
◦ [OH-] = 1.5 x 10-3 M
Practice
◦ Calculate the pH of a 1.40 x 10 -4 M solution of KOH.
◦ [OH-] = 1.40 x 10 -4 M