ACIDS AND BASES
ACID, BASE, OR NEUTRAL?
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Bitter taste
Doesn’t conduct electricity
Feels slippery
Dissolves metals
Has no odor
Has a strong, acrid odor
Turns litmus blue
Is unreactive
Feels sticky
Feels greasy
Turns phenolphthalein solution red
Dissolves grease
Bubbles when baking soda is added
Is oily
ARRHENIUS DEFINITION OF
ACID AND BASE
ACID – hydrogen
containing compound
that ionizes to yield
hydrogen ions (H+) in
aqueous solution
 BASE – compound
that ionizes to yield
hydroxide ions (OH-)
in aqueous solution
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IONIZABLE HYDROGENS
 Only
hydrogens in very polar bonds ionize.
Carboxyl group
This is the hydrogen
that ionizes in acetic
acid
 Some
acids have more than one ionizable
hydrogen
DIPROTIC ACIDS 2 ionizable hydrogens
(H2SO4 )
 TRIPROTIC ACIDS 3 ionizable hydrogens
(H3PO4 )

ARRHENIUS BASE OR ACID?
Ca(OH)2
 HNO3
 KOH
 C2H5COOH
 HBr
 H2SO4

Base
 Acid
 Base
 Acid
 Acid
 Acid
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BRONSTED-LOWRY DEFINITION
OF ACID AND BASE
ACID – hydrogen ion
(H+) donor
 BASE – hydrogen ion
(H+) acceptor
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IDENTIFY EACH REACTANT AS A
HYDROGEN DONOR (ACID) OR
HYDROGEN ACCEPTOR (BASE)
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HNO3 + H2O  H3O+ + NO3-
Water acts as
Base
both a hydrogen
(acceptor)
(donor)
donor and
CH3COOH + H2O  H3O+ + CH3COOhydrogen
Base
acceptor – it acts
Acid
(acceptor)
(donor)
as both an acid
and a base. It is
NH3 + H2O  NH4+ + OHAMPHOTERIC
Base Acid
Acid
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(acceptor)

(donor)
H2O + CH3COO-  CH3COOH + OHAcid
Base
(donor)
(acceptor)
CONJUGATE ACIDS & BASES
 CONJUGATE
ACID – formed when a base
gains a hydrogen ion
 CONJUGATE
BASE – formed when an acid
donates a hydrogen ion
NH3 and NH4+ are a
conjugate acid base pair
LABEL THE CONJUGATE ACIDBASE PAIRS
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HNO3 + H2O  H3O+ + NO3-
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CH3COOH + H2O  H3O+ + CH3COO-

NH3 + H2O  NH4+ + OH-
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H2O + CH3COO-  CH3COOH + OH-
LEWIS ACIDS AND
BASES
ACID – a substance
than can accept a pair
of electrons to form a
covalent bond
 BASE – a substance
than can donate a pair
of electrons to form a
covalent bond
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SELF-IONIZATION OF WATER
2H2O (L) ⇆ H3O+(aq) + OH-(aq)
At any given time, there are only VERY small amounts of
[H3O+] and [OH-] ions in water (1 molecule out of 550,000,000 dissociates)
 Water dissociates to form equal concentrations of H3O+
and OH- making water neutral
At 25◦C, Kw = [H+] [OH-] = [1 x 10-7 ] [1 x 10-7 ] = 1 x 10-14
ION-PRODUCT CONSTANT
OF WATER
ACIDIC SOLUTIONS VS. BASIC
SOLUTIONS
Acidic Solution
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[H+] is greater than [OH-]
[OH-] comes from selfionization of water
Extra [H+] comes from
substances that dissolve in
water to create [H+]
[H+] is greater than 1x10-7
Basic Solution
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[H+] is less than [OH-]
[H+] comes from selfionization of water
Extra [OH-] comes from
substances that dissolve in
water to create [H+]
[H+] is less than 1x10-7
Also known as alkaline
solution
ION CONCENTRATIONS IN
ACIDIC, NEUTRAL AND BASIC
SOLUTIONS
ACIDIC, BASIC OR NEUTRAL?
[H+] = 6.0 x 10-10 M
Basic (hydrogen ion concentration is less
than 1.0 x 10-7
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[OH-] = 3.0 x 10-2 M
[OH-][H+]= 1.0 x 10-14
[H+]= 1.0 x 10-14
3.0 x 10-2
[H+] = 3.3 x 10-13
Basic
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[H+] = 2.0 x 10-7 M
Acidic (hydrogen ion concentration is
greater than 1.0 x 10-7

[OH-] = 1.0 x 10-7 M
Neutral
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ACIDIC SOLUTIONS VS. BASIC
SOLUTIONS
Acidic Solution
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[H+] is greater than [OH-]
[OH-] comes from selfionization of water
Extra [H+] comes from
substances that dissolve in
water to create [H+]
[H+] is greater than 1x10-7
pH < 7.0
pOH > 7.0
Basic Solution
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[H+] is less than [OH-]
[H+] comes from selfionization of water
Extra [OH-] comes from
substances that dissolve in
water to create [H+]
[H+] is less than 1x10-7
Also known as alkaline
solution
pH > 7.0
pOH < 7.0
MEASURING PH
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Acid-Base
Indicators – an acid
or a base that:
Dissociates in known
pH range
 Acid and base forms
are different colors in
solution
 Accuracy challenged
by changes in temp &
human error
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pH meter
Quick
 Accurate within .01
pH units
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ACID RAIN
PH
& POH
pH = –log[H+]
 pOH = –log[OH-]
 pH + pOH = 14
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Use LOG key on
calculator not LN
to calculate pH!
 Use antilog (10x)
key on calculator
to calculate M
from pH
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SAMPLE PROBLEMS
What is the pH of a
solution if the [H+] is 8 x
10-11 M?
pH = -log[H+]
 pH = -log[8 x 10-11]
 pH = 10.10
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Some calculators
require that you push
LOG key first while
some require that you
put in the # first then
press LOG
What is the pOH of a solution
if the [OH-] is 2 x 10-3 M?
pOH = -log[OH-]
 pOH = -log[2 x 10-3 ]
 pOH = 2.70
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Some calculators may
keep giving you errors if
you try converting into –
log. Just calculate using
positive and switch the
answer sign
SAMPLE PROBLEMS
What is the pH & pOH of a
solution made by adding
water to 35 grams of nitric
acid until the volume of
the solution is 5800 mL?
What is the pH of a
solution if the [OH-] is 3.5
x 10-2 M?
pOH = -log[OH-]
 pOH = -log[3.5 x 10-2 ]
 pOH = 1.46
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pH + pOH = 14
 14 – 1.46 = pH
 12.54 = pH
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M = mol solute / L solution
35 g HNO3 / 63 g = .56 mol
M = .56 mol / 5.8 L = .097 M
 pH = -log[H+]
 pH = -log[.097 ]
 pH = 1.01
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pH + pOH = 14
14 – 1.01 = 12.99 = pOH
PLACE THE FOLLOWING COMPOUNDS IN
ORDER OF INCREASING [H+]
1M weak acid
 1M strong acid
 1M strong base
 1M weak base

1M strong base
 1M weak base
 1M weak acid
 1M strong acid
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WRITE THE EXPRESSION FOR THE ACID
DISSOCIATION CONSTANT OF THE STRONG ACID
HF:
HF(aq)  H+(aq) + F-(aq)
Ka = [H+ ][A- ]
[HA]
Ka = [H+ ][F- ]
[HF]
WRITE THE EXPRESSION FOR THE BASE DISSOCIATION
CONSTANT FOR THE WEAK BASE HYDRAZINE.
HYDRAZINE REACTS WITH WATER TO FORM N2H5+ ION
N2H4(aq) + H2O(l)  N2H5+ (aq) + OH-(aq)
Kb = [OH- ][N2H5+ ]
[N2H4]
PLACE THE FOLLOWING ACIDS IN ORDER FROM
WEAKEST TO STRONGEST (USE TABLE ON P.607)
HOOCCOOH
 HCO3 H2PO4 HCOOH
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HCO3 H2PO4 HCOOH
 HOOCCOOH
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A .10M SOLUTION OF FORMIC ACID HAS AN
EQUILIBRIUM [H+] = 4.2 X 10-3M. WHAT IS THE
KA OF FORMIC ACID?
HCOOH(aq)  H+(aq) + HCOO-(aq)
(4.2 x 10-3 ) (4.2 x 10-3 )
(.10 – 4.2x10-3 )
Ka = 1.8 x 10-4