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

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

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

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

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

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)

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

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

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

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

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

Problems The titration of a 20.ml of a sample of H2SO4 solution of unknown concentration requires 22.87ml 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?