Download - ACID BASE CHEMISTRY
ACID BASE CHEMISTRY
TERMS, ETC.
AMPHOTERIC:Subst. acts as either an acid or a base
Proton (Acidic p+): H+ ion; the acidic hydrogen(s) present in an acid
HNO3: one H+ H2SO4: two H+H3PO4: three H+
MONOPROTIC ACID: An acid w/ one H+
DIPROTIC ACID: An acid w/ two H+
POLYPROTIC ACID: An acid w/ 3 or more H+
HYDRONIUM ION:
H2O (l) + H+1 (aq) ---------> H3O+1 (aq)
Proton:H+; a hydrogen w/ characteristics like a proton itself -----1 p+, 0 n0, 0 e-
Acid BASE
All acids contain H+; when in water givesolution higher [H+]
All bases contain OH-;when in water givesolution higher [OH-]
Arrhenius
BRONSTAD – LOWRY
Acid
Any subst. thatdonates a proton; H+
BASE
Any subst. thataccepts a proton; H+
LEWIS Any subst. thataccepts an e- pair
Any subst. thatdonates an e- pair
ACIDS BASES
•Taste sour•Turns litmus blue -- red•Lowers pH
•Feels slippery•Turns litmus red -- blue•Increases pH
The stronger the acid the better it is at donating H+
STRONG ACIDSSTRONG ACIDS
HCl ; HBr ; HI ; HNO3 ; H2SO4 ; HClO4H+
+Cl-H++I- 2H++SO4
-
2
0 7 14
pH SCALE
STRONG ACIDIC
STRONG BASIC
MILDACIDIC
MILDBASIC
WEAK ACIDIC
WEAK BASIC
NEUTRAL ( )
Kw: constant for water, 1*10-14
ACID-BASE REACTIONS
HCl (aq) + KOH (aq) ---> KCl (aq) + HOH (l) acid base salt water
pH -- pOH -- [H+] -- [OH-] CALCULATIONS
Formulas to Use
-w OH H K
pOH pH pK w
Constants
Kw = 1 *10 –14
pH = -log [H+]
pOH = -log [OH-]
pKw = 14
Rules for LOGSLog 1 = 0
Log 10exp = exponent
[H+] = 1*10-pH
[OH-] = 1*10-pOH
Calculate pH for thefollowing solutions
1) [H+] = 1 * 10-9
2) [H+] = 0.001
pH = -log (1*10-9) = -(-9) = 9
0.001 = 1*10-3
pH = -log (1*10-3) = -(-3) = 3
3) [H+] = 3.6 * 10-2
pH = -log(3.6*10-2) = 1.44
OR-log 10-2 = 2 pH = 2 – log (3.6) = 2 – 0.56 = 1.44
Find pH & pOH
pOH pKw = pH + pOH 14 = 1.44 + pOHpOH = 14 – 1.44 = 12.56
OR
HK OH- w
2
14
10*6.310*1
= 2.78*10-13
pOH = 13 – log 2.78 = 13 – 0.44 =
If [H+] is 6.7*10-9 mol/L, what is the pH? ACIDIC, BASIC, NEUTRAL
What is the [OH-]? What is the pOH?
pH = -log(6.7*10-9) = 9 – log 6.7 = 9 – 0.83 = 8.17 BASIC
pOH = 14 – 8.17 = 5.83
[OH-] = 1*10-5.83
Find pH Find pOH
Find [OH-]
OR
= 1.49*10-6
CONJUGATE ACID-BASE PAIRS
Acid, loses H+, form conjugate base
Base, gains H+, forms conjugate acid
)(
-1
42(aq)3)(
-2
4)(
1
4 POH NH HPO NH aqaqaq
acid1 acid2base2 base1
CONJUGATE ACID-BASE PAIRS
(aq)3)(
1
4 NH NH
aq )(
-1
42)(
-2
4 POHHPO aqaq
TITRATIONS
Strong Acid + Strong Base ------ Neutral
Strong Acid + Weak Base --- Acidic
Weak Acid + Strong Base --- Basic
Weak Acid + Weak Base ---- ???????
+/- ions of acid not react w/ H2O
“+” ion of strong acid reacts w/ H2O, produces H3O+
“-” ion of strong base reacts to produce OH- ions
Both +/- ions react w/ H2O
STRENGTH
Strong Acid/Base ionize completely equilibrium lies far to the right HCl ------> H+ + Cl-
NaOH -----> Na+ + OH-
Weak Acid slightly ionize equilibrium lies far to the leftHC2H3O2 + H2O <-----> H+ + C2H3O2
-
]OH[HC
]OHC][OH[KO]H[K
O]H][OH[HC
]OHC][OH[K
232
-
2323a2eq
2232
-
2323eq
Ka: acid dissociation constantKb: base dissociation constant
IONIZATION CONSTANTS
Ka acetic acid = 1.8*10-5
Ka nitrous acid = 4.4*10-4nitrous acid more ionized in soln
BASE
NH3 + H2O <---> NH4+ +OH-
][NH
]OH][NH[KO]H[K
O]H][[NH
]OH][NH[K
3
-
4b2eq
23
-
4eq
Kb ammonia = 1.8*10-5
S.A.S.A. yields weak conjugate baseW.A.W.A. yields strong conj. base
MONOPROTIC ACIDS pg. 300
Ka Acid
1.2*10-2 HSO4-
1.2*10-2 HClO2
7.2*10-4 HF
1.8*10-5 HC2H3O2
3.5*10-8 HOCl
5.6*10-10 NH4+
8.3*10-13 SO4-2
8.3*10-13 ClO2-
1.4*10-11 F-
5.56*10-10 C2H3O2-
2.9*10-7 OCl-
1.8*10-5 NH3
Kb Conj. Base
Diprotic & Triprotic Acids
H2CO3: 2 acidic protons Ka values for each H+
H CO HCO
H HCO COH2-
3
-
3
-
332Ka1 = 4.3*10-7
Ka2 = 5.6*10-11
typically weak polyprotic acid Ka1 > Ka2 > Ka3
means???? -each step of dissociation is successively weaker-loss of 2nd & 3rd proton occurs less readily
Why???? should not be surprising think in terms of charges, +/- being attracted
S.A. : Ka 10-1 --- 10-3
W.A.: Ka 10-4 & smaller
Polyprotic acid: Ka value lowers w/ each H+ lost Loss of each additional H+ more difficult
H3PO4 + H2O <-----> H3O+ + H2PO4- Ka1
H2PO4- + H2O <-----> H3O+ + HPO4
-2 Ka2
HPO4-2 + H2O <-----> H3O+ + PO4
-3 Ka3
Ka1 > Ka2 > Ka3
10-3 10-8 10-
13
S.B.: Kb????
Ka: acid dissociation constant
HA + H2O <-----> H3O+ + A-
HA
AOH K
-
3
a
HNO3 + H2O <-----> H3O+ + NO3-
3
-
33
aHNO
NOOH K
BUFFER-used to control pH level of a soln.-either remove H+ or add OH- ions-usually W.A. & conj. Base
TITRATIONS.A. + W.B. -------> AcidicW.A. + S.B. -------> BasicS.A. + S.B. -------> NeutralW.A. + W.B. -----> ?? more info.
S.A. ------> weak conjugate BaseW.A. -----> strong conj. Base
Various Ways to Describe Acid Strength
Property S.A. W.A.
Ka value Ka is large Ka is small
Position of dissociation equilibrium
Far to right Far to left
Equilibrium [H+] compared to [HA]o
[H+] [HA]o [H+]<<[HA]o
Strength of conj.base compared to H2O
A- much weaker acid than H2O
A- much stronger base than H2O
INTERMOLECULAR FORCES
Forces that act between diff. molecules
Gases: <<< forces, act independently of each other
Liquids/Solids: >>>> Forces
KEY PTS.
Stronger the Force -------- more difficult to separate atoms/molecules
---- higher melting/boiling pts of subst.
3 MAJOR FORCES
Dipole-DipoleDipole-Dipole London DispersionLondon Dispersion
Polar Cov. Bonds “net polarity”
Weak Force
+/- ends of molecules align together
Dipole-Dipole London Dispersion Hydrogen Bonding
All molecules; behavior due to e- movement w/i subst.
Nonpolar molecules form temporary Polarity
Weak Force; as mole.wt.
Surface Area: > S.A. ---- > Force stronger the molecule held together