Date ______
Chapter 15 Section 1 Notes
The Concept of pH
The symbol [ ] with a formula enclosed means concentration in moles per liter.
For pure water at 25°C, the concentrations of H3O+ and OH- in pure water are 1.0 x 10-7 mol/L.
In water at 25°C, [H3O+] = 1.0 x 10-7 M and [OH-] = 1.0 x 10-7 M
The mathematical product of [H3O+] and [OH-] remains constant in water and dilute aqueous solutions at constant temperature. This constant mathematical product is called the ionization constant of water, Kw, and is expressed by the following equation.
Because the hydronium ion and hydroxide ion concentrations are the same in pure water, it is neutral. Any solution in which [H3O+] = [OH-] is also neutral.
Solutions in which the [H3O+] is greater than the [OH-] are acidic.
In basic solutions, the [OH-] is greater than the [H3O+].
Calculating [H3O+] and [OH-]:
1. Determine the hydronium and hydroxide ion concentrations in a solution that is
1 × 10-4 M HCl.
2. Determine the hydronium and hydroxide ion concentrations in a solution that is
1.0 × 10-3 M HNO3 .
3. Determine the hydronium and hydroxide ion concentrations in a solution that is
3.0 × 10-2 M NaOH.
4. Determine the hydronium and hydroxide ion concentrations in a solution that is
1.0 × 10-4 M Ca(OH)2 .
1. Determine the pH of the following solutions:
a. 1 × 10-3 M HCl
b. 1 × 10-5 M HNO3
c. 1 × 10-4 M NaOH
d. 1.0 × 10-2 M KOH
1. What is the pH of a solution if the [H3O+] is 6.7 × 10-4 M?
2. What is the pH of a solution with a hydronium ion concentration of 2.5 × 10-2M?
3. Determine the pH of a 2.5 × 10-6 M HNO3 solution.
4. Determine the pH of a 2.0 × 10-2 M Sr(OH)2 solution.
1. The pH of a solution is determined to be 5.0. What is the hydronium ion concentration of this solution?
2. The pH of a solution is determined to be 12.0. What is the hydronium ion concentration of this solution?
3. The pH of an aqueous solution is measured as 1.50. Calculate the [H3O+] and the [OH-].
4. The pH of an aqueous solution is 3.67. Determine [H3O+].
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