Acid Base Ch. 15 & 16 notes

Acid Base Notes

Ch. 15 part I
Arrhenius, Bronsted-Lowry and Lewis (skipped)

Arrhenius
Electrolytes: material that dissolves in water to give a solution that conducts an electric current
a. strong electrolyte: material when dissolved in water gives a solution that
conducts large electric current (high percent of ionization)

b. weak electrolyte: material when dissolved in water gives a solution that
conducts small electric current (lower percent of ionization)
EX: weak acids and bases, partially soluble salts
Arrhenius Acid: furnishes a hydrogen ion in water (H+)
Arrhenius Base: furnishes a hydroxide ion in water (OH-)

Conjugate Acids and Bases
HCl + NaOH --> HOH + Na Cl
HCl + OH- --> HOH + + Cl-

Acid + Base --> conjugate acid (accepts proton) + conjugate base ( what is left behind)
Study p.467

Monoprotic (one hydrogen) – HCl
Diprotic (two hydrogen) – H2SO4
Triprotic (three hydrogens) – H3PO4

Amphoteric Substances: act as either acid or base p. 470 e.g. water is amphoteric

pH = -log [H3O+]
[H3O+] is the concentration in molarity of the hydronium ion

Ex. #1 If [H3O+]= 1 ee-7 M then
pH = - log [1 e-7M] = - (-7) = 7

Ex. #2 If [H3O+]= 1 ee-2 M then
pH = - log [1 e-2M] = - (-2) =2

pH + pOH = 14
Ex: pOH = 3, then pH = 11 (OH- concentration is high 1 ee-3 then [H3O+] =1 ee-11, very small number, this solution is basic)

Different pH Indicators turn different colors at different pH’s (e.g. phenolphthalein turns pink in the presence of a base)

Titrations:
Quantity of one reactant is compared to quantity of another
Neutralization reaction: acid + base = water + salt
Equivalence point the quantities of acid and base are exactly equal
Indicators: dyes that indicate when equivalence point is reached (weak acid or base)
Calculations the same as solution dilutions:(M1 x V1 = M2 x V2)
Molarity acid x Volume acid = Molarity base x Volume base

Titrations: Ma xVa = Mb x Vb
Ex: (0.01 M HCl) (20.0 ml) = (.02 M NaOH) ( ? ml)
Solve for the amount of 0.02 base required to neutralize the 0.01 M acid.
Anhydrides
Without water
Acid anhydride: substance added to water form acids
Basic anhydride: substance added to water form base

If diprotic like H2SO4 with NaOH then,

2xMa xVa = Mb x Vb

Acids and Bases General Information

Arrhenius
Electrolytes: material that dissolves in water to give a solution that conducts an electric current
a. strong electrolyte: material when dissolved in water gives a solution that
conducts large electric current (high percent of ionization)

b. weak electrolyte: material when dissolved in water gives a solution that
conducts small electric current (lower percent of ionization)
EX: weak acids and bases, partially soluble salts
Arrhenius Acid: furnishes a hydrogen ion in water (H+)
Arrhenius Base: furnishes a hydroxide ion in water (OH-)

Bronsted-Lowry
Hydronium ion: H3O+ forms when a proton is transferred from HCl to a water molecule
Conjugate acid: forms when proton is transferred to base
Conjugate acid: everything left after proton given up
B-L acid: substance that can donate a proton
B-L base: substance that can accept proton

Lewis
electrophile - seeks an electron: Lewis acid (electron pair acceptor
nucleophile - seeks a nucleus: Lewis base (electron pair donor)
pH = -log [H+]
pOH = -log [OH-]

Acid Base Notes part II

Rules for Acid/Base Strength
Binary: HCl, HBr HI strong all others weak
Ternary: the number of Oxygen atoms exceeds number of H atoms by 2 or more, the acid is strong
Polyprotic acids: donate more than one proton – 2nd and 3rd are always weak
Bases: hydroxides of IA and IIA are strong (except Be), all others are weak
If Keq is < 1, then reactants are favored
If Keq is >1, then products are favored
Ka acid dissociation constant
Kb base dissociation constant

pH = -log [H+]
pOH = -log [OH-]
pKw = pH + pOH

Titration
Quantity of one reactant is compared to quantity of another
Neutralization reaction: acid + base = water + salt
Equivalence point the quantities of acid and base are exactly equal
Indicators: dyes that indicate when equivalence point is reached (weak acid or base)

Anhydrides
Without water
Acid anhydride: substance added to water form acids
Basic anhydride: substance added to water form base

Hydrolysis
The reaction of a salt with water to produce an acidic or basic or neutral solution
1. If salt is derived from strong acid and strong base, the solution is neutral pH=7, ex: NaCl
2. If salt is derived from weak acid and a strong base, the solution is a base pH > 7, ex: sodium acetate
3. If salt is derived from strong acid and weak base, the solution is an acid pH < 7, ex: ammonium bromide

Buffers
A mixture that contains a conjugate acid – base pair
EX: buffer is made with 0.200 mole of HF and 0.100 mole of NaF in water to make 1.0 L with a Ka of 6.8 x 10-4