1. pH and Titration Notes
Honors Chemistry

2. pH measure of the strength of acids and bases pH = power of hydrogen
pH = -log [H+]
logarithmic scale – so when you change a number on the scale, you change by a factor of 10
pH 3 is 10 times less acidic than pH 2
pH 1 is 100 times more acidic as pH 3

3. pH of Common Substances

4. pOH measures strength of the hydroxide ion pOH = -log [OH-]
highest value of pH or pOH = 14
lower value of pOH = stronger base
pH + pOH = 14
if find one of the values, then subtract from 14 to find the other
example: if pH is 3, then pOH is 11 (14-3 = 11)

5. Example pH Calculations
[H+] = 1 x 10-5 M
pH = -log (1 x 10-5)
pH = 5
Calculate the pH for the following:
[H+] = 1 x 10-2
[H+] = 3.0 x 10-6
[H+] = 8.2 x 10-8
[H+] = 9.5 x 10-11

6. Converting pH to [H+] use: 10-pH = [H+]
example: pH = 5.3, so = 5.01 x 10-6 M
Calculate the [H+] for the following:
pH = 2.37
pH = 7.25
pH = 11.05
pH = 6.50

7. Example pOH Calculations
[OH-] = 4 x 10-3 M
pOH = - log (4 x 10-3) = 2.40
Calculate the pOH for the following:
[OH-] = 2.3 x 10-12
[OH-] = 5.8 x 10-5
[OH-] = 9.0 x 10-8
[OH-] = 7.45 x 10-3

8. Converting pOH to [OH-]
use: 10-pOH = [OH-]
example: pOH = 2.8, so = 1.58 x 10-3
Calculate the [OH-] for the following:
pOH = 11.2
pOH = 3.46
pOH = 8.77
pOH = 7.0

9. More pH/pOH Calculations
A/B/N
3.2 x 10-3
1.26 x 10-5
10.3
7.89

10. Neutralization
reaction between an acid and a base in which their acidic and basic properties disappear
Acid + Base  Salt + Water
salt = metal and a non-metal
ex. HCl + NaOH  NaCl + H2O
ex. HCl + Ca(OH)2  CaCl2 + H2O

11. Titration
technique used by chemists to determine the unknown concentration of a substance using a neutralization reaction
uses an indicator to tell when reaction has reached neutralization
indicator – chemical that is one color in an acid and another color in a base
end point – the point in the reaction when neutralization has occurred and the indicator changes color

12. Acid-Base Indicators
An acid – base indicator changes color when it is in a solution of a certain pH.
Red litmus paper turns blue and is used as an indicator of a basic solution that would have a pH above 7.
Blue litmus paper turns red and is used as an indicator of an acidic solution that would have a pH below 7.
Phenolphthalein is also a common kind of acid – base indicator. It turns clear in an acid and pink in a base.

13. Titration Equation
when reaction in titration is neutral, moles of acid = moles of base
moles = molarity (M) x volume (V)
so use the equation:
Moles Acid = Moles Base
M1V1 = M2 V2

14. Titration Example 1
What is the molarity of a CsOH solution if 30.0 mL of the solution is neutralized by 26.4 mL of a M HBr solution?

15. Titration Example 2
What is the molarity of a nitric acid solution if mL of a M KOH solution is needed to neutralize 20.0 mL of HNO3?

16. Titration Example 3
What is the concentration of a household ammonia cleaning solution if 49.9 mL of a 0.59 M HCl solution is required to neutralize 25.0 mL of ammonia solution?

17. Titration Example 4
A titration of 50 mL of an unknown concentration of NaOH solution uses a 0.5 M HCl solution. The buret containing HCl initially reads 49.8 mL and reads 22.5 mL after the end point is reached. What is the molarity of the NaOH solution?