7/30/2019 Concepts of Acid Base Neutralization
1/75
7/30/2019 Concepts of Acid Base Neutralization
2/75
An electrolyteis a substance that, when dissolved in water, results
in a solution that can conduct electricity.
A nonelectrolyteis a substance that, when dissolved, results in a
solution that does not conduct electricity.
nonelectrolyte weak electrolyte strong electrolyte
ELECTROLYTIC PROPERTIES
7/30/2019 Concepts of Acid Base Neutralization
3/75
METHOD OF DISTINGUISHING BETWEENELECTROLYTES AND NONELECTROLYTES
A pair of inert electrodes (Cu or Pt) is immersed in a beaker
of water.
To light the bulb, electric current must flow from one
electrode to the other, thus completing the circuit.
By adding NaCl (ionic compound), the bulb will glow.
NaCl breaks up into Na+ and Cl- ions when dissolves in water.
Na+ are attracted to the negative electrode.
Cl- are attracted to the positive electrode.
The movement sets up an electric current that is equivalent to
the flow of electrons along a metal wire.
7/30/2019 Concepts of Acid Base Neutralization
4/75
Strong Electrolyte
100% dissociation (breaking up of compound intocations and anions
NaCl (s) Na+ (aq) + Cl- (aq)H2O
Weak Electrolyte
not completely dissociated
CH3COOH CH3COO- (aq) + H+ (aq)
A reversiblereaction. The reaction can occur in
both directions.
7/30/2019 Concepts of Acid Base Neutralization
5/75
7/30/2019 Concepts of Acid Base Neutralization
6/75
Hydrationis the process in which an ion is surrounded by
water molecules arranged in a specific manner.
Hydration helps to stabilize ions and prevents cations fromcombining with anions.
d+d-
H2O
d+
7/30/2019 Concepts of Acid Base Neutralization
7/75
Nonelectrolyte does not conduct electricity?
No cations (+) and anions (-) in solution
C6H12O6 (s) C6H12O6 (aq)H2O
7/30/2019 Concepts of Acid Base Neutralization
8/75
Have a sour taste.- Vinegar owes its taste to acetic acid.
- Citrus fruits contain citric acid.
React with certain metals to produce hydrogen gas.
React with carbonates and bicarbonates to produce carbon
dioxide gas
Cause color changes in plant dyes.
2HCl (aq) + Mg (s) MgCl2 (aq) + H2 (g)
2HCl (aq) + CaCO3 (s) CaCl2 (aq) + CO2 (g) + H2O (l)
Aqueous acid solutions conduct electricity.
PROPERTIES ACIDS
7/30/2019 Concepts of Acid Base Neutralization
9/75
Have a bitter taste.
Feel slippery. Many soaps contain bases.
Cause color changes in plant dyes.
Aqueous base solutions conduct electricity.
Examples:
PROPERTIES OF BASES
7/30/2019 Concepts of Acid Base Neutralization
10/75
ROLE OF WATER TO SHOW PROPERTIES OF
ACIDS
Anhydrous pure acid (without water) does not show acidicproperties.
In dry form, acids exist as neutral covalent molecules.
Dry acids do not dissociate to form hydrogen ion (H+).
When a pure acid is dissolved in water, it will show the
properties of acids.
This is because acids will dissociate in water to form H+ or
hydroxonium/hydronium ion, H3O+ which are free to move.
For example:
i) HCl in liquid methylbenzene (organic solvent) - does not
show acidic properties.
ii) HCl in watershow acidic properties
7/30/2019 Concepts of Acid Base Neutralization
11/75
ROLE OF WATER TO SHOW PROPERTIES OF
ALKALI
Dry base does not show alkaline properties.
A base in dry form, contains hydroxide ions (OH-) that are
not free to move. Thus, the alkaline properties cannot be
shown. In the presence of water, bases can dissociate in water to
form hydroxide ions, OH-, which are free to move. Thus,
alkaline properties are shown.
For example:i) ammonia in tetrachlomethane (organic solvent)do not
show alkaline properties
ii) ammonia in watershow alkaline properties
7/30/2019 Concepts of Acid Base Neutralization
12/75
DEFINITION OF ACID AND BASE
Arrhenius Brnsted-
LowryLewis
7/30/2019 Concepts of Acid Base Neutralization
13/75
Arrhenius acid is a substance that produces H+ (hydrogen ion)
or hydronium ion(H3O+) in water
Arrhenius base is a substance that produces OH- in water
DEFINITION OF ACID AND BASE BY ARRHENIUS
7/30/2019 Concepts of Acid Base Neutralization
14/75
Examples of acid:
CO2
(g) + H2
O (l) H2
CO3
(aq)
H2CO3 (aq) + H2O(l) H3O+ (aq) + HCO3
- (aq)
nonmetal oxides + H2O acid
Examples of bases:
NaOH (s) Na+ (aq) + OH- (aq)
N2H4 (aq) + H2O N2H5+ (aq) + OH- (aq)
metal oxides + H2O bases
Na2O (s) + H2O (l) 2NaOH (aq)
* Limited only to aqueous solutions
7/30/2019 Concepts of Acid Base Neutralization
15/75
A Brnsted acid is a proton donor
A Brnsted base is a proton acceptor
Example:
acid base acid base
A Brnsted acid must contain at least one ionizable
proton!
DEFINITION OF ACID AND BASE BY BRNSTED-LOWRY
HCl (aq) +H2O (l) H3O+ (aq) + Cl- (aq)
HCl is a acid because it donates proton to H2O
H2O is a base because it accepts proton from HCl
7/30/2019 Concepts of Acid Base Neutralization
16/75
Brnsted acids and bases
Conjugate acid-base pair:
i) Conjugate base of a Brnsted acid
- the species that remains when one proton has beenremoved from the acid
ii) Conjugate acid
- addition of a proton to a Brnsted base
7/30/2019 Concepts of Acid Base Neutralization
17/75
Examples:
HCl (aq) +H2O (l) H3O+ (aq) + Cl- (aq)
acid1 base2 acid2 base1
Cl- is a conjugate base of HCl and HCl is a conjugate acid of Cl-
H2O is a base conjugate of H3O+ and H3O
+ is a acid conjugate of
H2O
NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)
base1 acid2 acid1 base2
subscripts 1 and 2 = two conjugate acid-base pair
7/30/2019 Concepts of Acid Base Neutralization
18/75
When a strong acid react with a strong base in Brnsted acid-base
reaction, it will give a weak conjugate acid and conjugate base.
Examples:
HCl (aq) + H2O (l) H3O+ (aq) + Cl- (aq)
strong acid strong base weak conjugate weak conjugateacid base
NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)
Weak base weak acid strong conjugate strong conjugate
acid base
H2O can function as acid or base which called amphoteric
Amphoteric or amphiprotic substance is one that can react as
either an acid or base
7/30/2019 Concepts of Acid Base Neutralization
19/75
Identify each of the following species as a Brnsted acid, base, or
both. (a) HI, (b) CH3COO-, (c) H2PO4
-
HI (aq) H+ (aq) + I- (aq) Brnsted acid
CH3COO- (aq) + H+ (aq) CH3COOH (aq) Brnsted base
H2PO4- (aq) H+ (aq) + HPO4
2- (aq)
H2PO4- (aq) + H+ (aq) H3PO4 (aq)
Brnsted acid
Brnsted base
7/30/2019 Concepts of Acid Base Neutralization
20/75
7/30/2019 Concepts of Acid Base Neutralization
21/75
A Lewis acidis a substance that can accept a pair of electrons
A Lewis baseis a substance that can donate a pair of electrons
H+ H O H
+ OH-
acid base
N HH
H
H+ +
acid base
N H
H
H
H+
DEFINITION OF ACID AND BASE BY LEWIS
7/30/2019 Concepts of Acid Base Neutralization
22/75
Examples of Lewis Acids and Bases reactions:
N HH
H
acid base
F B
F
F+ F B
F
F
N H
H
H
b) Ag+ (aq) + 2NH3 (aq) Ag(NH3)2+ (aq)
acid base
c) Cd+ (aq) + 4I- (aq) CdI2-4 (aq)
acid base
d) Ni (s) + 4CO (g) Ni(CO)4 (g)
acid base
a)
7/30/2019 Concepts of Acid Base Neutralization
23/75
7/30/2019 Concepts of Acid Base Neutralization
24/75
7/30/2019 Concepts of Acid Base Neutralization
25/75
Acidsi) Strong acids:
- Acids that completely ionized in solution.
- Example:
HCl (aq) H+ (aq) + Cl- (aq)
ii) Weak acids
-Acids that incompletely ionized in solution
- Example:
CH3COOH (aq) CH3COO- (aq) + H+ (aq)
TYPES OF ACIDS-BASES
7/30/2019 Concepts of Acid Base Neutralization
26/75
7/30/2019 Concepts of Acid Base Neutralization
27/75
Monoprotic acid:
- each unit of the acid yields one hydrogen ion upon
ionization
HCl H+ + Cl-
HNO3 H+ + NO3
-
CH3COOH H+ + CH3COO-
Strong electrolyte, strong acid
Strong electrolyte, strong acid
Weak electrolyte, weak acid
Diprotic acid:
- each unit of the acid gives up two H+
ions, in two separatesteps
H2SO4 H+ + HSO4
-
HSO4- H+ + SO4
2-
Strong electrolyte, strong acid
Weak electrolyte, weak acid
7/30/2019 Concepts of Acid Base Neutralization
28/75
Triprotic acids:
- yield three H+ ions
H3PO4 H+ + H2PO4
-
H2PO4- H+ + HPO4
2-
HPO42- H+ + PO4
3-
Weak electrolyte, weak acid
Weak electrolyte, weak acid
Weak electrolyte, weak acid
7/30/2019 Concepts of Acid Base Neutralization
29/75
Bases
i) Strong bases:
- Bases that completely ionized in solution.
- Example:
NaOH (s) Na+ (aq) + OH- (aq)
ii) Weak bases
- bases that incompletely ionized in solution
- Example:
NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)
7/30/2019 Concepts of Acid Base Neutralization
30/75
Acids and bases as electrolytes
Strong acids such as HCl and HNO3 are strongelectrolytes, while weak acid such as acetic acid(CH3COOH) is a weak electrolyte.
HCl (aq) + H2O (l) H3O+ (aq) + Cl- (aq)
HNO3 (aq) + H2O (l) H3O+ (aq) + NO3
- (aq)
HClO4 (aq) + H2O (l) H3O+ (aq) + ClO4- (aq)
H2SO4 (aq) + H2O (l) H3O+ (aq) + HSO4
- (aq)
7/30/2019 Concepts of Acid Base Neutralization
31/75
Strong Acidsare strong electrolytes
HCl (aq) + H2O (l) H3O+ (aq) + Cl- (aq)
HNO3 (aq) + H2O (l) H3O+ (aq) + NO3
- (aq)
HClO4 (aq) + H2O (l) H3O+ (aq) + ClO4
- (aq)
H2SO4 (aq) + H2O (l) H3O+ (aq) + HSO4
- (aq)
Acids and bases as electrolytes
HF (aq) + H2O (l) H3O+
(aq) + F-
(aq)
Weak Acidsare weak electrolytes
HNO2 (aq) + H2O (l) H3O+ (aq) + NO2
- (aq)
HSO4- (aq) + H2O (l) H3O
+ (aq) + SO42- (aq)
H2O (l) + H2O (l) H3O+
(aq) + OH-
(aq)
7/30/2019 Concepts of Acid Base Neutralization
32/75
Strong Basesare strong electrolytes
NaOH (s) Na+ (aq) + OH- (aq)H
2O
KOH (s) K+ (aq) + OH- (aq)H2O
Ba(OH)2 (s) Ba2+ (aq) + 2OH- (aq)
H2O
F- (aq) + H2O (l) OH- (aq) + HF (aq)
Weak Basesare weak electrolytes
NO2- (aq) + H2O (l) OH
- (aq) + HNO2 (aq)
7/30/2019 Concepts of Acid Base Neutralization
33/75
Conjugate acid-base pairs:
The conjugate base of a strong acid has no measurable
strength.
H3
O+ is the strongest acid that can exist in aqueous solution.
The OH- ion is the strongest base that can exist in aqueous
solution.
7/30/2019 Concepts of Acid Base Neutralization
34/75
7/30/2019 Concepts of Acid Base Neutralization
35/75
H2O (l) H
+
(aq) + OH
-
(aq)
autoionizationof water
Can act either as a acid or as a base.
Water functions as a base with acids such as HCl and
CH3COOH and function as acid in reaction with bases. Water is a very weak electrolyte and undergo ionization to a
small extent:
ACID-BASE PROPERTIES OF WATER
h d f
7/30/2019 Concepts of Acid Base Neutralization
36/75
H2O (l) H+ (aq) + OH- (aq)
The Ion Product of Water
Kc=[H+][OH-]
[H2O]
[H2O] = constant
Kc
= equilibrium constant
Kc[H2O] = Kw= [H+
][OH-
]
The ion-product constant(Kw) is the product of the molar
concentrations of H+ and OH- ions at a particular temperature.
At 250C
Kw= [H+][OH-] = 1.0 x 10-14
[H+] = [OH-]
[H+] > [OH-]
[H+] < [OH-]
Solution Isneutral
acidic
basic
7/30/2019 Concepts of Acid Base Neutralization
37/75
What is the concentration of OH- ions in a HCl solution whosehydrogen ion concentration is 1.3 M?
Kw= [H+][OH-] = 1.0 x 10-14
[H+] = 1.3 M
[OH-] =Kw
[H+]
1 x 10-14
1.3= = 7.7 x 10-15M
7/30/2019 Concepts of Acid Base Neutralization
38/75
7/30/2019 Concepts of Acid Base Neutralization
39/75
pH = -log [H+]
[H+] = [OH-]
[H+] > [OH-]
[H+] < [OH-]
Solution Is
neutral
acidic
basic
[H+] = 1 x 10-7
[H+] > 1 x 10-7
[H+] < 1 x 10-7
pH = 7
pH < 7
pH > 7
At 250C
pH [H+]
pH-A MEASURE OF ACIDITY
pHthe negative logarithm of the hydrogen in
concentration (in mol/L)
Oth i t t l ti hi
7/30/2019 Concepts of Acid Base Neutralization
40/75
pOH = -log [OH-]
[H+][OH-] = Kw= 1.0 x 10-14
-log [H+]log [OH-] = 14.00
pH + pOH = 14.00
Other important relationships
pH Meter
7/30/2019 Concepts of Acid Base Neutralization
41/75
1) The pH of rainwater collected in a certain region of the
northeastern United States on a particular day was 4.82. What is
the H+ ion concentration of the rainwater?
pH = -log [H+]
[H+] = 10-pH= 10-4.82 = 1.5 x 10-5M
2) The OH- ion concentration of a blood sample is 2.5 x 10-7 M.
What is the pH of the blood?
pH + pOH = 14.00
pOH = -log [OH-] = -log (2.5 x 10-7) = 6.60
pH = 14.00pOH = 14.006.60 = 7.40
7/30/2019 Concepts of Acid Base Neutralization
42/75
7/30/2019 Concepts of Acid Base Neutralization
43/75
7/30/2019 Concepts of Acid Base Neutralization
44/75
CALCULATION OF pH FORSOLUTION CONTAINING A
STRONG ACID AND ASOLUTION OF A STRONG
BASE
1) i f 2 10 3 O i ?
7/30/2019 Concepts of Acid Base Neutralization
45/75
1) What is the pH of a 2 x 10-3 MHNO3 solution?
HNO3 is a strong acid100% dissociation.
HNO3 (aq) + H2O (l) H3O+ (aq) + NO3
- (aq)
pH = -log [H+
] = -log [H3O+
] = -log(0.002) = 2.7
Start
End
0.002 M
0.002 M 0.002 M0.0 M
0.0 M 0.0 M
2) What is the pH of a 1.8 x 10-2MBa(OH)2 solution?
Ba(OH)2 is a strong base100% dissociation.
Ba(OH)2 (s) Ba2+ (aq) + 2OH- (aq)
Start
End
0.018 M
0.018 M 0.036 M0.0 M
0.0 M 0.0 M
pH = 14.00pOH = 14.00 + log(0.036) = 12.6
7/30/2019 Concepts of Acid Base Neutralization
46/75
HA (aq) + H2O (l) H3O+ (aq) + A- (aq)
Weak Acids (HA) and Acid Ionization Constants
HA (aq) H+ (aq) + A- (aq)
Ka= [H+
][A-
][HA]
Kais the acid ionization constant
Kaweak acid
strength
7/30/2019 Concepts of Acid Base Neutralization
47/75
1) Wh t i th H f 0 5M HF l ti ( t 250C)?
7/30/2019 Concepts of Acid Base Neutralization
48/75
1) What is the pH of a 0.5MHFsolution (at 250C)?
HF (aq) H+ (aq) + F- (aq) Ka=[H+][F-]
[HF]= 7.1 x 10-4
HF (aq) H+ (aq) + F- (aq)
Initial (M)
Change (M)
Equilibrium (M)
0.50 0.00
-x +x
0.50 - x
0.00
+x
x x
Ka=x2
0.50 - x= 7.1 x 10-4
Ka x20.50 = 7.1 x 10-40.50x 0.50K
a
7/30/2019 Concepts of Acid Base Neutralization
49/75
When can I use the approximation?
0.50x 0.50Ka
7/30/2019 Concepts of Acid Base Neutralization
50/75
Solving weak acid ionization problems:
1. Identify the major species that can affect the pH.
In most cases, you can ignore the autoionization of water.
Ignore [OH-] because it is determined by [H+].
2. Use ICE to express the equilibrium concentrations in terms of
single unknown x.
3. Write Kain terms of equilibrium concentrations. Solve for x
by the approximation method. If approximation is not valid,
solve for xexactly.
4. Calculate concentrations of all species and/or pH of the
solution.
7/30/2019 Concepts of Acid Base Neutralization
51/75
1) What is the pH of a 0.122Mmonoprotic acid whose
Kais 5.7 x 10-4?
HA (aq) H+ (aq) + A- (aq)
Initial (M)
Change (M)
Equilibrium (M)
0.122 0.00
-x +x
0.122 - x
0.00
+x
x x
Ka=x2
0.122 - x= 5.7 x 10-4
Ka
x2
0.122 = 5.7 x 10-4
0.122x 0.122Ka
7/30/2019 Concepts of Acid Base Neutralization
52/75
Ka=x2
0.122 - x= 5.7 x 10-4 x2 + 0.00057x6.95 x 10-5 = 0
ax2 + bx+ c=0-b b24ac
2ax=
x= 0.0081 x= - 0.0081
HA (aq) H+ (aq) + A- (aq)
Initial (M)
Change (M)
Equilibrium (M)
0.122 0.00
-x +x
0.122 - x
0.00
+x
x x
[H+] = x= 0.0081 M
pH = -log[H+] = 2.09
W k B d B I i ti C t t
7/30/2019 Concepts of Acid Base Neutralization
53/75
NH3
(aq) + H2O (l) NH
4
+ (aq) + OH- (aq)
Weak Bases and Base Ionization Constants
Kb=[NH4
+][OH-]
[NH3]
Kbis the base ionization constant
Kbweak base
strength
Solve weak base problems like weak acids exceptsolve for
[OH-] instead of [H+].
7/30/2019 Concepts of Acid Base Neutralization
54/75
CONCENTRATION OF SOLUTION
7/30/2019 Concepts of Acid Base Neutralization
55/75
The concentrationof a solution is the amount of solute
present in a given quantity of solvent or solution.
M= molarity=moles of solute
liters of solution
1) What mass of KI is required to make 500. mL of a 2.80
MKI solution?
volume of KI solution moles KI grams KIMKI M KI
500. mL = 232 g KI166 g KI
1 mol KIx
2.80 mol KI
1 L solnx
1 L
1000 mLx
CONCENTRATION OF SOLUTION
7/30/2019 Concepts of Acid Base Neutralization
56/75
Preparing a Solution of Known
Concentration
7/30/2019 Concepts of Acid Base Neutralization
57/75
7/30/2019 Concepts of Acid Base Neutralization
58/75
DILUTION OF SOLUTIONS
7/30/2019 Concepts of Acid Base Neutralization
59/75
Dilutionis the procedure for preparing a less concentrated solution
from a more concentrated solution.
DilutionAdd Solvent
Moles of solute
before dilution (i)
Moles of solute
after dilution (f)=
MiVi MfVf=
DILUTION OF SOLUTIONS
EXAMPLE
7/30/2019 Concepts of Acid Base Neutralization
60/75
EXAMPLE:
1) How would you prepare 60.0 mL of 0.200 MHNO3
from a stock solution of 4.00 MHNO3?
MiVi = MfVf
Mi = 4.00 M Mf= 0.200 M Vf= 0.0600 L Vi = ? L
Vi =MfVf
Mi=
0.200 Mx 0.0600 L
4.00 M= 0.00300 L = 3.00 mL
Dilute 3.00 mL of acid with water to a total volume of 60.0 mL.
Concentration Units
7/30/2019 Concepts of Acid Base Neutralization
61/75
Concentration Units
The concentrationof a solution is the amount of solute present
in a given quantity of solvent or solution.
Percent by Mass (%w/w)
% by mass = x 100%mass of solute
mass of solute + mass of solvent
= x 100%mass of solute
mass of solution
7/30/2019 Concepts of Acid Base Neutralization
62/75
Percent by Volume (%v/v)
% by volume = x 100%
Volume of solute
Volume of solution
Mole Fraction (X)
XA =moles of A
sum of moles of all components
7/30/2019 Concepts of Acid Base Neutralization
63/75
M=moles of solute
liters of solution
Molarity (M )
Molality (m)
m=moles of solute
mass of solvent (kg)
7/30/2019 Concepts of Acid Base Neutralization
64/75
Quantitative analytical process based on measuringvolumes.
The most common form of VA is the titration, aprocess whereby a standard solution of knownconcentration is chemically reacted with a solutionof unknown concentration in order to determine theconcentration of the unknown.
VOLUMETRIC ANALYSIS (VA)
7/30/2019 Concepts of Acid Base Neutralization
65/75
In a titrationa solution of accurately known concentration(standard solution) is added gradually added to another solution
of unknown concentration until the chemical reaction between the
two solutions is complete.
Equivalence pointthe point at which the reaction is complete
Indicatorsubstance that changes color at (or near) the
equivalence point
TITRATIONS
Titrations can be used in the analysis of acid-base reactions
H2SO4 + 2NaOH 2H2O + Na2SO4
7/30/2019 Concepts of Acid Base Neutralization
66/75
Slowly add base
to unknown acid
UNTIL
the indicator
changes color
PROCEDURE FOR THE TITRATION
7/30/2019 Concepts of Acid Base Neutralization
67/75
EXAMPLE
7/30/2019 Concepts of Acid Base Neutralization
68/75
EXAMPLE:
1) What volume of a 1.420 MNaOH solution is required to titrate
25.00 mL of a 4.50 MH2SO4 solution?
WRITE THE CHEMICAL EQUATION!
volume acid moles red moles base volume base
H2SO4 + 2NaOH 2H2O + Na2SO4
4.50 mol H2SO4
1000 mL solnx
2 mol NaOH
1 mol H2SO4x
1000 ml soln
1.420 mol NaOHx25.00 mL = 158 mL
M
acid
rxn
coef.
M
base
ACID-BASE TITRATIONS
7/30/2019 Concepts of Acid Base Neutralization
69/75
Strong Acid-Strong Base Titrations
NaOH (aq) + HCl (aq) H2
O (l) + NaCl (aq)
OH- (aq) + H+ (aq) H2O (l)
pH PROFILE OF THE TITRATION (TITRATION CURVE)
7/30/2019 Concepts of Acid Base Neutralization
70/75
Before addition of NaOH
- pH = 1.00
When the NaOH added
- pH increase slowly at first
Near the equivalence point (the point which equimolar
amounts of acid and base have reacted)
- the curve rises almost vertically
Beyond the equivalence point
- pH increases slowly
pH PROFILE OF THE TITRATION(TITRATION CURVE)
CALCULATION OF Ph AT EVERY STAGE OF
7/30/2019 Concepts of Acid Base Neutralization
71/75
TITRATION
1) After addition of 10.0 mL of 0.100 M NaOH to 25.0 mL of 0.100 M
HCl
Total volume = 35.0 mL
Moles of NaOH in 10.0 mL
= 10.0 mL x 0.100 mol NaOH x 1L
1L NaOH 1000 mL
= 1.00 x 10-3 mol
Moles of HCl in 25.0 mL
= 25.0 mL x 0.100 mol HCl x 1L
1 L HCl 1000 mL
= 2.50 x 10-3 mol
7/30/2019 Concepts of Acid Base Neutralization
72/75
Amount of HCl left after partial neutralization
= (2.50 x 10-3)-(1.00 x 10-3)
= 1.50 x 10-3 mol
Concentration of H+ ions in 35.0 mL
1.50 x 10-3 mol HCl x 1000 mL = 0.0429 M HCl
35.0 mL 1L
[H+] = 0.0429 M,
pH = -log 0.0429 = 1.37
2) After addition of 25.0 mL of 0.100 M NaOH to 25.0 mL 0f 0.100 MHCl
[H+] = [OH-] = 1.00 x 10-7
pH = 7.00
3) After addition of 35.0 mL of 0.100 M NaOH to 25.0 mL of 0.100 mL
7/30/2019 Concepts of Acid Base Neutralization
73/75
of HCl
Total volume = 60.0 mL
Moles of NaOH added
= 35.0 mL x 0.100 mol NaOH x 1L1 L NaOH 000 mL
= 3.50 x 10-3 mol
Moles of HCl in 25.0 mL solution = 2.50 x 10-3 mol
After complete neutralization of HCl, no of moles of NaOH left= (3.50 x 10-3)-(2.50x10-3)
= 1.00 x 10-3 mol
Concentration of NaOH in 60.0 mL solution
= 1.00 x 10
-3
mol NaOH x 1000 mL60.0 mL 1L
= 0.0167 M NaOH
[OH-] = 0.0167 M
pOH = -log 0.0167 = 1.78
pH = 14.001.78
= 12.22
Exactly 100 mL of 0.10 MHNO2 are titrated with a 0.10 M
7/30/2019 Concepts of Acid Base Neutralization
74/75
NaOH solution. What is the pH at the equivalence point ?
HNO2 (aq) + OH- (aq) NO2- (aq) + H2O (l)
start (moles)
end (moles)
0.01 0.01
0.0 0.0 0.01
NO2- (aq) + H2O (l) OH- (aq) + HNO2 (aq)
Initial (M)
Change (M)
Equilibrium (M)
0.05 0.00
-x +x
0.05 - x
0.00
+x
x x
[NO2-] =
0.01
0.200= 0.05 MFinal volume = 200 mL
Kb=[OH-][HNO2]
[NO2-]
=x2
0.05-x= 2.2 x 10-11
0.05x
0.05 x
1.05 x 10
-6
= [OH
-
]
pOH = 5.98
pH = 14pOH = 8.02
Acid-Base Indicators
7/30/2019 Concepts of Acid Base Neutralization
75/75
HIn (aq) H+(aq) + In-(aq)
10[HIn][In
-
]
Color of acid (HIn) predominates
10[HIn][In-]
Color of conjugate base (In-) predominates