1. 9.4 pH and Titrations Obj S5, S6, and S7
Chemistry

2. Essential Questions
How do the H+ and OH- concentrations compare for acidic, basic, and neutral solutions?
What is pH and how is it used to identify if something is an acid or base?
What is a neutralization reaction?
What are indicators?
What are titrations?
How are titrations used to find out concentration or volume of an unknown?

3. Hydrogen Ions from Water
The reaction in which water molecules produce ions is called the self-ionization of water.
In neutral solutions H+ and OH- are equal in concentration
Basic solutions have more OH- and acidic solutions have more H+

4. Hydrogen Ions from Water
In the self-ionization of water, a proton (hydrogen ion) transfers from one water molecule to another water molecule.
The self-ionization of water. A proton (hydrogen ion) transfers from one water molecule to another water molecule. The result is one hydronium ion (H3O+) and one hydroxide ion (OH-).

5. Ion Product Constant for Water
The product of the concentrations of the hydrogen ions and hydroxide ions in water is called the ion-product constant for water (Kw).
This is why a pH of 7 is neutral and the pH scale goes to 14

6. pH [H+]= 10-pH (unit is M H+)
pH is defined as the negative log of the hydrogen ion concentration.
pH = - log [H+]
Acids are substances with a pH < 7.
Bases are substances with a pH >7.
Pure water is neutral and has pH = 7.
[H+]= 10-pH (unit is M H+)

8. pH (cont)
As pH increases the H+ concentration decreases and OH- concentration increases

9. Identifying Acids and Bases
A solution where [H+] = 1.0 x 10-3
A solution where [H+] = 1.0 x 10-7
A solution where [H+] = 6.99 x 10-9
A solution where [H+] = 1.0 x 10-13
A solution where [H+] = 5.0 x 10-5
A solution where [H+] = 7.5 x 10-8

10. Identifying Acids and Bases (cont)
Find [H+] given the following pHs
4.3
7.8 13
2.13

11. Neutralization Reactions
Neutralization reactions are where an acid and base react to form neutral products of salt and water
Salt: ionic compound formed from acid and base
KOH (aq)+ HCl (aq)→ KCl (aq)+ H2O (l)
Base
Acid
Salt
Water

12. Acid-Base indicators
An acid-base indicator is a substance that changes colors when exposed to acids or bases.
Example: Phenolphthalein turns pink in a base and remains colorless in an acid.
Red Cabbage juice has several different colors depending on the pH.

15. Acid-Base Titration
Titration is a technique in which a standard solution is added little by little to determine the concentration of an unknown substance using a neutralization reaction.
The standard solution is a solution where you know its concentration.
Indicators are used to determine the point when the acid and base have neutralized each other.

16. Acid-Base Titration (cont)
The point at which the two solutions are chemically equivalent and fully reacted is called the Equivalence point.
The end point is when the indicator first permanently changes color and should be a similar point in the reaction to the equivalence point.

17. Calculations for Acid-Base Titration
Molarity of Known
Volume of known =
Unknown Molarity x
Unknown volume x
Example: In a titration, 17.6 mL of acetic acid is used to neutralize 27.4 mL of a solution that is M potassium hydroxide. What is the concentration of the acetic acid solution?
(17.6 mL acid) (x) = (27.4 mL base)( 0.215M)
X = (27.4ml)(0.215M)/(17.6ml) = .335 M acetic acid

18. Titration Problems
Find the mL of 5.5 M KOH when reacted with 32 mL of 4.23 M HF
Find the mL of 7.9 M HC2H3O2 when reacted with 611 mL of 9.0 M NH3
Find the concentration of H2CO3 when 43 mL of 1.2 M NH3 is added to 66 mL of H2CO3
Find the concentration of 97 mL SO4- when 54 mL of 2.44 M HF is added to it.

19. Essential Questions
How do the H+ and OH- concentrations compare for acidic, basic, and neutral solutions?
What is pH and how is it used to identify if something is an acid or base?
What is a neutralization reaction?
What are indicators?
What are titrations?
How are titrations used to find out concentration or volume of an unknown?

20. 9.4 Tracked Assignment
worksheet