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Acids, Bases and Salts
Version 1.0
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Acid Properties
• sour taste
• change the color of litmus from blue to
red.
These properties are due to the release
• react with of hydrogen ions, H+, in water solution.
– metals such as zinc and magnesium to
produce hydrogen gas
– hydroxide bases to produce water and an
ionic compound (salt)
– carbonates to produce carbon dioxide.
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Base Properties
• bitter or caustic taste
• a slippery, soapy feeling.
• the ability to change litmus red to
blue
• the ability to interact with acids
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Uses of acids and bases
Many of the things we eat & use today are made
up of acids and bases.
Examples:

Sulfuric acid-car batteries,acid rain

Hydrochloric acid-stomach acid
Sodium hydrogen carbonate-baking soda and
cooking

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Uses of Acids/ Bases Contd.
, DNA,the building block of life, stores
genetic information.


Amino acids, the building blocks of proteins.
Found in movies: Acids in Jurassic Park
(DNA) and in Aliens (acidic blood).

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Arrhenius Acid/Base Definition
• Svante Arrhenius was a Swedish
scientist who lived from 1859-1927.
• In 1884 he advanced a theory of acids
and bases.
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An Arrhenius acid “is a hydrogencontaining substance that dissociates
to produce hydrogen ions.”
HA → H+ + AAcid
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An Arrhenius base is a hydroxidecontaining substance that dissociates
to produce hydroxide ions in aqueous
solution.
MOH → M+(aq) + OH-(aq)
Base
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An Arrhenius acid solution contains an excess of H+ ions
because an Arrhenius acid increases H+ concentration,
when dissolved in water.
An Arrhenius base solution contains an excess of OH- ions
because it increases OH- concentration, when dissolved in
water.
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Bronsted and Lowry Definition
• J.N. Bronsted (1897-1947) was a
Danish chemist and T. M. Lowry
(1847-1936) was an English chemist.
• In 1923 they advanced their theory of
acids and bases.
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A Bronsted-Lowry acid is a proton (H+) donor.
A Bronsted-Lowry base is a proton (H+) acceptor.
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proton acceptor
Bronsted-Lowry
Acid
Bronsted-Lowry
Base
proton
donor
HCl (aq) + H2O(l) → H3O+(aq) + Cl-(aq)
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Conjugate acid-base pairs differ by a
single proton.
1. Are sulphate and sulfuric acid conjugate acid
and base of each other? Why or why not?
2. Write conjugate base of H3PO4.
3. Write conjugate acid of NO3-
1. No, they differ by 2 protons. 2. H3PO4. 3. HNO3
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. A strong acid has a weak conjugate base and vice
versa.
List of strong Acids: HCl, HNO3, H2SO4, HI, HBr,
HClO3, HClO4
List of Strong Bases: All group 1 and 2 metal
hydroxides
Monoprotic Acids: Have one proton that can be
donated. Ex. HCl, HNO3, H C2H3O2
Diprotic Acids: Have two protons that can be
donated. H2SO4
Polyprotic Acids: Have more than two protons that
can be donated. Ex. H3PO4
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Compare the strengths of two acids in the following
reactions. What does the strength of acid have to do with the
direction in which this reaction occurs? (Forward reaction is
favored, why?)
HCl(g) + H2O (l) → Cl-(aq) + H3O+(aq)
Acid
1
Base
2
Base
1
Acid
2
If strong acid will completely ionize
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Lewis Acids and Bases
• In 1923 G. N. Lewis developed a more
comprehensive theory of acids and bases.
• The Lewis theory deals with the way in
which a substance with an unshared
pair of electrons reacts in an acid-base
type of reaction.
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A Lewis acid is an electron-pair acceptor.
A Lewis base is an electron-pair donor.
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Electron
Pair
Lewis Acid
Acceptor
Electron pair
donated to H+
Lewis
Base
Electron
Pair Donor
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Reactions of Acids
In aqueous solution, the H+ or H3O+ ions are
responsible for the characteristic reactions of
acids.
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Reaction with Bases The reaction of an acid
with a base is called a neutralization reaction.
In an aqueous solution the products are a salt
and water:
HBr(aq) + KOH(aq) → KBr(aq) + H2O(l)
acid
base
salt
2HNO3(aq) + Ca(OH)2(aq) → Ca(NO3)2(aq) + 2H2O(l)
acid
base
salt
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The reaction of an acid with a base is called a
neutralization reaction. In an aqueous solution
the products are a salt and water:
HBr(aq) + KOH(aq) → KBr(aq) + H2O(l)
acid
base
salt
2HNO3(aq) + Ca(OH)2(aq) → Ca(NO3)2(aq) + 2H2O(l)
acid
base
salt
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Salts can be considered compounds
derived from acids and bases. They consist
of positive metal or ammonium ions
combined with nonmetal ions (OH- and
O2- excluded).
Salts are usually
Chemists
use thecrystalline
terms ionic
and compound
have high
and saltand
melting
interchangeably.
boiling points.
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Salt Formation
The negative
positive ion
ion of
the salt is derived
from the acid.
base.
base NaOH
HCl acid
NaCl
salt
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Ionization of Water
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hydroxide
ion
Water ionizes slightly.
hydronium ion
H2O + H2O →
→ H3O+ + OHacid
→
base
acid
base
Water ionization equilibrium can be expressed more
simply as:
Kw= [H3O+] [OH-] = 1.0 x 10-14 mol/L (This
expression can be used to calculate H+ or OH-)
[H3O+] or [H+]= [OH-] = 1.0 x 10-7 mol/L
What is [OH-], if [H+] is 3.0 x 10-3? ( ans: 3.3 X 10 –12 )
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Two out of every 1 billion water molecules are ionized
.
Introduction to pH
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The pH Scale
The pH of a solution is defined as the negative of the common logarithm of the
hydronium ion concentration.
pH= -log [H3O+]
The pOH of a solution is defined as the negative of the common logarithm of the
hydroxide ion concentration.
pOH= -log[OH-]
[H3O+]
1.0
Increasing acidity
1.0x10-7
Increasing basicity
1.0x10-14
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Calculation of pH
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[H+] = 1.0 X 10 ^-14/ [OH-]
H+
OH[OH-] = 1.0 X 10 ^-14/ [H+]
pOH= -log [OH-]
[OH-]= 10^-pOH
[H+]= 10^-pH
pH= -log [H+]
pH BOX
pOH= 14- pH
pOH
pH
pH= 14- pOH
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pH = -log[H+]
[H+] = 1 x 10-5
when this number
is exactly 1
pH = this number
without
pHthe
= 5minus
sign.
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pH = -log[H+]
[H+] = 2 x 10-5
when this number is
one significant figure
between 1 and 10
pH is between this
number and next
ph = 4.7
lower number (4 and
one decimal place
5).
The number of decimal places of a logarithm is
equal to the number of significant figures in the
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original number.
What is the pH of a solution with an [H+] of 1.0 x 10-11?
2 significant figures
pH = - log(1.0 x 10-11)
pH = 11.00
2 decimal places
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What is the pH of 0.002 M
H2SO4?
[H+] = 2 x 10-3
pH = - log(2 x 10-3)
pH = 2.7
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1. What is the pH of 0.003 M NaOH?
[OH-] = 3 x 10-3
pOH = - log(3 x 10-3)
pOH = 2.2 14.0-2.2 = 11.8
2. What is [H+], if pH is 3.4?
10
-3.4 =
4 X 10 -4
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The pH scale of Acidity and Basicity
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15.4
Neutralization
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Neutralization: The reaction of an acid and
a base to form a salt and water.
HCl(aq) + KOH(aq) → KCl(aq) + H2O(l)
acid
base
salt
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Titrations
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titration: The process of measuring the
volume of one reagent required to react with
a measured mass or volume of another
reagent.
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42.00 mL of 0.150 M NaOH solution is required to
neutralize 50.00 mL of hydrochloric acid solution.
What is the molarity of the acid solution?
The equation for the reaction is
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
acid
base
salt
Calculate the liters of NaOH that react.
mol
Molarity =
L
1L 

= 0.04200
 42.00 mLThe

unit of volume
when L


Convert
mL
of NaOH to
1000
mL

using molarity is liters.
liters of NaOH
Calculate the moles of NaOH that react.
0.150 mol NaOH 

 0.004200 L  
 = 0.00630 mol NaOH
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1L


42.00 mL of 0.150 M NaOH solution is required to
neutralize 50.00 mL of hydrochloric acid solution.
What is the molarity of the acid solution?
The equation for the reaction is
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
acid
base
salt
The moles
mole ratio
of NaOH
of HClthat
to NaOH
react equals
is 1:1 the moles of
HCl that react.
0.00630 mol NaOH react. 0.00630 mol HCl react.
The molarity of the HCl solution is
mol 0.0630 mol HCl
M=
=
 0.126 M HCl 42
L
0.05000 L
Writing Net Ionic Equations
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In the un-ionized equation all compounds
are written using their molecular or formula
expressions.
HCl(aq) + KOH(aq) → KCl(aq) + H2O(l)
acid
base
salt
In the total ionic equation all ions present in
solution are written.
(H+ + Cl-) + (K+ + OH-) → K+ + Cl- + H2O
that do notonly
participate
in a chemical
In the net ionicIons
equation
the
ions
that react
+
Cl
ion
does
K
ion
not
does
react.
not
react.
reaction are called spectator ions.
are written.
H+(aq) + OH-(aq) → H2O(l)
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