1. Warm up Why you use an antacid when you have heartburn?

2. Acid Base Reactions
Acids – Substance that produce H+ ions in an aqueous solution
Base – Substance that produce OH- in aqueous solution
This is the Arrhenius definition for acids and bases

3. In aqueous solutions, H+ ions combine with water to form hydronium ion
H+(aq) + H2O(aq) H3O+(aq)
Chemists use H+ or H3O+ to represent a hydronium ion

4. The ionization reaction of HCl in water can be represented by the equation
HCl(aq) + H2O(aq) H3O+(aq) +Cl-(aq)
Polyprotic Acids – Acids contains more than one ionizable protons

5. Polyprotic acids
Acids produces more than one ionizable proton
Example : H2SO4
H2SO4(aq) ↔ H+ (aq)+ HSO4- (aq) HSO4-(aq) ↔ H+(aq) + SO4 2- (aq)

6. Base is a substance that release OH- ions in aqueous solution
Example : NaOH
NaOH (aq) Na+(aq) + OH-(aq)
Some bases produce more than one OH- in the solution
Example: Sr(OH)2(aq)

8. Acid base reactions
Acid +Base = salt +water
Example : Reaction between HCl and NaOH
Reaction between H2SO4 and KOH

9. Write molecular and net ionic equations
HI(aq) and Ba(OH)2(aq)
H2SO4(aq) and LiOH(aq)

10. Acid –Base Titrations
In titrations a substance in known concentration reacts with another substance of unknown concentration
example: titration of HCl against NaOH

11. Theory of acid base titration
Conside the reaction between HCl and NaOH
Write the ionic equation and eliminate the spectator ions
As the OH- ion is added, it reacts with H+ and neutralize it forming water

12. At some point the amount of OH- added will be equivalent to the number of H+ ions – equivalence point
We use an indicator to signal the equivalence point.
Indicator : Phenolphthalein is a dye used as an indicator

13. Problems
The titration of a 20.ml of a sample of H2SO4 solution of unknown concentration requires ml of a 0.518M KOH solution to reach the equivalent point. What is the concentration of the unknown H2SO4 solution?
What volume in ml of 0.2M NaOH do we need to titrate 35.00ml of 0.140M HBr to the equivalence point?