1
ACID- BASEEQUILIBRIA
H O l2 ( )
NO aq H O aq31
31 ( ) ( )
ACID- BASEEQUILIBRIAACID- BASEEQUILIBRIAACID- BASEEQUILIBRIA
LEWIS ACIDS & BASESACID = ELECTRON PAIR ACCEPTORBASE = ELECTRON PAIR DONOR
MUST HAVE AN UNSHARED PAIR OF ELECTRONS TO DONATE TO THE COVALENT BOND BETWEEN THE ACID AND BASE
H+ + NH3 NH41+
H+ +
H
N H
H
:
H
H N H
H
+
Al3+ + 6 H2O Al(H2O)6
H2O + SO3 H2SO4
BF3 + NH3 BF3 - NH3
BRONSTED - LOWRYBRONSTED ACIDS AND BASES
SPECIAL CASE OF THE LEWIS ACID-BASE THEORYACID IS A PROTON DONOR H+
BASE IS A PROTON ACCEPTOR
MUST HAVE UNSHARED PAIR OF ELECTRONS
O + NH3
ooC
H3C
O
O Ho o
o oC
H3C
O
o o
o ooo- + NH4
1
THAT IS, MUST BE A LEWIS BASE
ACID - BASE REACTION NEUTRALIZATION
PROTON BOUND TO A VERY ELECTRONEGATIVE ATOM
NOT AN ACID PROTON
ACID:
ARRHENIUS: PRODUCES H1+ IN WATER
BASE:
ARRHENIUS: PRODUCES OH1- IN WATER
BRONSTED: PROTON DONOR
BRONSTED: PROTON ACCEPTOR
LEWIS: HAS EMPTY ORBITAL
LEWIS: HAS e- PAIR AVAILABLE TO SHARE
+
SALT + WATERNEUTRALIZATION
DIFFERENCE: BRONSTED ACID HAS A PROTON!
NAMING ACIDS
BINARY:
UNLESS DISSOLVED IN WATER -- COVALENT
HBr
HYDROGENHYDRO BROMIDEBROMICHYDROBROMIC ACID
HFHI
HYDROFLUORIC ACIDHYDROIODIC ACID
POLYATOMICANIONS
-ITE = OUS OR -ATE = ICEXCEPTING S OR P
CO3 2- CARBONATE IONH2 CO3 IC ACID
SO42- = SULFATE ION H2 SO4 = SULFURIC ACID
SO32- = SULFITE ION H2 SO3 = SULFUROUS ACID
ACID BASE
BASE ACID
CONJUGATE
CONJUGATE
BRONSTED ACID-BASE CONJUGATE PAIRS
HCOOH (aq) + H2 O (l) HCOO1- (aq) + H3 O1+ (aq)
HOBr (aq) + H2 O (l) OBr1- (aq) + H3 O1+ (aq)
CONJUGATECONJUGATE
CONJUGATECONJUGATE
CONJUGATE PAIRS DIFFER BY A SINGLE PROTON!!!
O + NH3o
oC
H3C
O
O Ho o
o oC
H3C
O
o o
o ooo
- + NH41
CH3COOH (aq) + NH3 (aq) CH3COO1- (aq) + (aq)NH41
]NH][COOHCH[
]NH][COOCH[K
33
14
13
a
IF K >> 1, DISSOCIATION IS EXTENSIVEREACTION IS EXTENSIVE
IF K << 1, DISSOCIATION IS NOT EXTENSIVE
THE LARGER THE VALUE OF K, THE MORE EXTENSIVEIS THE REACTION
H2S (aq) + H2O (l) HS1- (aq) + H3O1+ (aq)
K = [HS1-] [H3O1+]
[ H2S]a
Kb = 1 X 10-14 / KaTHE LARGER THE VALUE OF K, THE STRONGER IS THE
ACID OR THE BASE
FOR ACID: THE MORE H3O1+ ION IS PRODUCED
FROM ACID - BASE CHART:
HIGH Ka + HIGH Kb = EXTENSIVE REACTION
RESULT: K>1 IF PRODUCT IS THE WEAKER ACID OR BASE OF THE CONJUGATE PAIR
ACID-BASE STRENGTH
BINARYHA
STRENGTH OF THE HA BOND
ELECTRONEGATIVITY OF A
OXOACID(OXYANION)
X-O- H
OXIDATION STATE OF XELECTRONEGATIVITY OF X
USUALLY: STRONGER BOND = WEAKER ACID
RESULT: K>1 IF PRODUCT IS THE WEAKER ACID OR BASE OF THE CONJUGATE PAIR
]OH[
]OH[K
13
13
a
H2O (l) + H301+ H2O (l) + H301+
WEAK ACID:Ka < Ka FOR H3O1+ Ka << 1
STRONG ACIDS:HX WHERE X = Cl, Br, IHNO3, HClO4, H2SO4
WEAK BASE:Kb < Ka FOR H3O1+ Kb << 1
STRONG BASE: SOLUBLE METAL HYDROXIDE
H2O (l) + H2O (l) H3O1+ (aq) + OH1- (aq)
K = Kw = [H3O1+][OH1-] = 1.0 x 10-14 AT 25 oC
[H3O1+] > [OH1-] ACIDIC SOLUTION
[H301+] = [OH1-] NEUTRAL SOLUTION
[H3O1+] < [OH1-] BASIC SOLUTION
[H3O1+] = [OH1-] = 1.0x10-7 M
pH = -log [H3O1+]
<7
= 7
>7
pK = -logKa
-log[1.0x10-7 ]
pKa + pKb = 14pH + pOH = 14 Ka x Kb = 1.0 x 10-14
0 2 4 6 7 8 10 12 14
14 12 10 8 7 6 4 2 0
pOH
pH
Scales to determine Acidity or Alkalinity
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
NEUTRAL
ACIDIC
BASIC
GASTRIC JUICE, 0.1 M HClORANGE JUICE
COKE, VINEGAR
WINETOMATO, BEERBLACK COFFEE
RAINSALIVA URINEHUMAN MILKBLOOD, TEARS
SEAWATER, EGG WHITEBILEBAKING SODA
BORAX
NAIR
HOUSEHOLD AMMONIADRAIN CLEANER,
0.1 M NaOH
14
WHAT IS THE pH of:
A. SOLUTION WHERE [H3O1+] = 3.6x10-6 MB. 0.25 M HClC. SOLUTION WHERE [OH1-] = 2.5x10-3 M
WHAT IS THE [OH1-] CONC. OF A pH = 4.5 SOLUTION?
pH = -log[H3O1+] Kw = [H3O1+][OH1-]= 1.0 x 10-14
A. pH = - LOG[3.6x10-6] = 5.4 (AN ACIDIC SOLUTION)
B. pH = -LOG[0.25] = 0.60
C. [H3O1+] [2.5x10-3] = 1.0x10-14= 4.0x10-12
pH = -LOG[4.0x10-12] = 11.4 (A BASIC SOLUTION)
[3.2x10-5][OH1-] = 1.0 x 10-14
[H3O1+] = 10-pH = 10-4.5 = 3.2x10-5
= 3.1x10-10 M
[H+] pH [OH-] pOHAcid, Base or Neutral
10-9
10-4
8
9
10-7
6
5
Titration Sample problem
• What volume of 1.0 M HCl is needed to neutralize 30.0 mL of 2.5 M NaOH?
Try These:
• What is the molarity of 5.0 mL of acid used to neutralize 10.0 mL of 2.5 M base?
• What volume of 1.0 M base is needed to neutralize 20.0 mL of 2.3 M acid?
Top Related