Acids & Bases Chapter 21

Properties of Acids & Bases Acids Acids Taste sour Taste sour React with carbonates & bicarbonates to make CO 2 React with carbonates & bicarbonates to make CO 2 React with metals to make H 2 gas (acids corrode metals) React with metals to make H 2 gas (acids corrode metals) Turn litmus paper red Turn litmus paper red

Bases Bases Taste bitter Taste bitter Feel slippery (emulsify fats & proteins) Feel slippery (emulsify fats & proteins) Turn litmus paper blue Turn litmus paper blue React with acids React with acids Both Acids & Bases: Both Acids & Bases: Are electrolytes & conduct electricity Are electrolytes & conduct electricity Neutralize each other, forming salt & water Neutralize each other, forming salt & water Properties of Acids & Bases

Defining Acids & Bases Acids & bases can ionize (produce ions) Acids & bases can ionize (produce ions) Arrhenius definition of Acids Arrhenius definition of Acids Produce H+ in waterHCl  H+ + Cl- Produce H+ in waterHCl  H+ + Cl- H+ bonds with H 2 O to make H 3 O+ H+ bonds with H 2 O to make H 3 O+ H 3 O+ is called hydronium H 3 O+ is called hydronium Arrhenius definition of Bases Arrhenius definition of Bases Produce OH- in waterNaOH  Na+ + OH- Produce OH- in waterNaOH  Na+ + OH- OH- is called hydroxide OH- is called hydroxide BUT some substances don’t make H 3 O+ or OH- and some acids/bases aren’t in a water solution! H 3 O+ H2OH2O

Defining Acids & Bases Bronsted-Lowry definition of Acids Bronsted-Lowry definition of Acids Acids donate protons (H+) Acids donate protons (H+) May not form hydronium May not form hydronium Bronsted-Lowry definition of Bases Bronsted-Lowry definition of Bases Bases accept protons Bases accept protons Don’t have to be Don’t have to be dissolved in water Some compounds Some compounds can behave as either Whether some substances act as acids or bases depends on other reactants

NH 3 accepts a proton to become NH 4 + NH 3 accepts a proton to become NH 4 + It is a Bronsted-Lowry base It is a Bronsted-Lowry base This reaction doesn’t have to happen in water This reaction doesn’t have to happen in water It is not an Arrhenius base because it doesn’t form OH- It is not an Arrhenius base because it doesn’t form OH-

Water can ionize! (form ions) Ionization = water breaking covalent bonds of molecules to form ions Ionization = water breaking covalent bonds of molecules to form ions H 2 O + H 2 O  OH- + H 3 O+ H 2 O + H 2 O  OH- + H 3 O+ Forms hydroxide & hydronium Forms hydroxide & hydronium 1 liter has 10^-7 mol hydronium & hydroxide 1 liter has 10^-7 mol hydronium & hydroxide Ionized molecules in dynamic equilibrium (constantly changing but total amount stays the same) Ionized molecules in dynamic equilibrium (constantly changing but total amount stays the same)

Homework: SRQ 21A 1-5

Monoprotic Acids Monoprotic Acids Only donate one hydrogen (Ex: HCl) Only donate one hydrogen (Ex: HCl) Diprotic Acids Diprotic Acids Can give two hydrogen Can give two hydrogen Polyprotic Acids Polyprotic Acids Can donate more than one H Can donate more than one H Ex: H 2 SO 4, H 2 CO 3, H 3 C 6 H 5 O 7 Ex: H 2 SO 4, H 2 CO 3, H 3 C 6 H 5 O 7 H that can be donated are called ionizable H that can be donated are called ionizable Ionizable H written 1st Ionizable H written 1st Acids can be described by how many H they have to give… H H

Conjugate Pair After donating a proton, an acid becomes its own conjugate base After donating a proton, an acid becomes its own conjugate base acid base Base becoming a conjugate acid (and then changing back)

Conjugate Pairs Which is the acid and which is the base? Which is the acid and which is the base? Now which is the acid and which is the base? Now which is the acid and which is the base? Conjugate Pair

After receiving a proton (acting as a base), water becomes its own conjugate acid After receiving a proton (acting as a base), water becomes its own conjugate acid Conjugate Pair

Homework: SRQ 21A 7, 10, & 11 and CRQ 1-3 & 5-10