Acid-Base EquilibriapH and pOH• Relationship of Conjugate Pair acid-base strength.• When acids or bases control pH:

determine K predict pH

• When pH controls acid/base state: predict acid/base state use acid/base state to determine pH

• Buffer action• pH titration curves

+ -2 3

-14 + -a 3

2 H O H O + OH

K = 1.0 10 = [H O ][OH ]

pH/pOH Calculations

[H3O+][OH-] = 1.0 x 10-14

pH = -log[H3O+] pOH = -log[OH-]

[H3O+] = 10-pH [OH-] = 10-pH

pH + pOH = 14.00

What is the pH of a solution with [H3O+] = 4.6 x 10-5

What is the pOH of a solution with [OH-] = 3.3 x 10-4

What is the pOH of a solution with [H3O+] = 2.4 x 10-3

What is [H3O+] when pH = 4.2

Strong acids and basesFor strong acid solutions, [H3O+] = [acid] (except for H2SO4)

For strong bases LiOH, NaOH, KOH, RbOH, [OH-] = [base]

For strong bases Ca(OH)2, Ba(OH)2, etc., [OH-] = 2 x [base]

What is the pH when [H3O+] = 0.045 M?

1. 2. 3. 4.

25% 25%25%25%1. 0.0452. 13.9953. -1.354. 1.35

What is the pH when [OH-] = 6.5 x 10-4 M?

1. 2. 3. 4.

25% 25%25%25%1. 3.182. -3.183. 10.814. 15.18

What is the [H3O+] when pH = 3.66 M?

1 2. 3 4.

25% 25%25%25%1. 2.18 x 10-4

2. 10.343. 45704. 3.66

What is the [OH-] when pH = 5.84 M?

1 2 3 4.

25% 25%25%25%1. 1.45 x 108

2. 3.31 x 10-6

3. 6.92 x 10-9

4. 5.84

Acid-Base EquilibriaBronsted Acid: H+ (proton) donorBronsted Base: H+ acceptor

Acid-Base reactions: H+ transfer reaction

Conjugate Acid-Base Pairs: acid conjugate base HF F-

NH4+ NH3

What is the conjugage base of HNO2?

1 2 3

33% 33%33%1. H2NO2+

2. HNO3

3. NO2-

What is the conjugage acid of HPO42-?

1 2 3

33% 33%33%1. H2PO4-

2. H3PO4

3. PO43-

Acid-Base Strength: Depends on Equilibrium Constant

Trends in relative acid/base strength for conjugate pairs.

Determining the Ka Value

What is the value of Ka for an acid, HA, for which a 0.240 M solution has a pH of 3.28?

Determining Kb:

A 0.300 M solution of a weak base has a pH of 9.20. What is Kb?

What is the pH of a 0.150 M solution of HCl?

What is the pH of a 0.150 M solution of HF?

What is the pH of a 0.150 M solution of HCN?

What is the pH of a 0.150 M solution of Ca(OH)2?

What is the pH of a 0.150 M solution of NH3?

Polyprotic Acids

H2CO3 HCO3- CO3

2-

H3PO4 H2PO4 - HPO4

2- PO4 3-