Introduction to
Acids, Bases and Salts
Arrhenius Definition of
Acids and Bases
 Acids produce H+ in aqueous (water) solutions
water
H+ (aq) + Cl- (aq)
HCl
 Bases produce OH- in aqueous (water) solutions
water
NaOH
Na+ (aq) + OH- (aq)
The Hydronium Ion (H30+)

Acids produce the H+ ion

This is just a “bare proton”
and is very reactive.

It immediately forms a
coordinate covalent bond
with nearby water
molecules to form (H30+).
Acids

Produce H+ (as H3O+) ions in water

Electrolytes (conduct in solution)

Taste sour

pH is < 7

Corrode metals (see Table J)

React with bases to form salts and water
(Neutralization)
Bases
Produce OH- ions in water
 Electrolytes (conduct in solution)
 Taste bitter, chalky
 pH is >7
 Feel soapy, slippery
 React with acids to form salts and water
(Neutralization)
Learning Check
Describe the solution in each of the following
as: 1) acid 2) base or 3)neutral.
A. ___soda
B. ___soap
C. ___coffee
D. ___ wine
E. ___ water
F. ___ grapefruit
7
Solution
Describe each solution as:
1) acid 2) base or 3) neutral.
A. _1_ soda
B. _2_ soap
C. _2_ coffee
D. _1_ wine
E. _3_ water
F. _1_ grapefruit
8
Learning Check
Identify each as characteristic of an
A) acid or B) base
____ 1. Sour taste
____ 2. Produces OH- in aqueous solutions
____ 3. Chalky taste
____ 4. Is an electrolyte
____ 5. Produces H+ in aqueous solutions
9
Solution
Identify each as a characteristic of an
A) acid or B) base
_A_ 1. Sour taste
_B_ 2. Produces OH- in aqueous solutions
_B_ 3. Chalky taste
A, B 4. Is an electrolyte
_A_ 5. Produces H+ in aqueous solutions
10
Some Common Acids
See Table K
HCl
hydrochloric acid
HNO3
nitric acid
H3PO4
phosphoric acid
H2SO4
sulfuric acid
HC2H3O2
acetic acid
11
Naming Acids (Honors)

Binary Acids

(Contain 2 elements only)

Ex:
HCl, HBr, H2S, HF
Hydro
__________ ic Acid
Naming Acids (Honors)

Ternary Acids
(Contain hydrogen and a polyatomic ion)
 Do NOT start with “Hydro”


Look at name of polyatomic ion

If it ends in “ate” the acid ends in “ic”

If it ends in “ite” the acid ends in “ous”
Name These Acids
 HBr
 HClO
 HNO3
 HBrO
 H3PO4
 HClO4
 HNO2
 H2S
 H2C2O4
 HIO3
Name These Acids
HBr = hydrobromic acid
HNO3 = nitric acid
HClO = hypochlorous acid
HBrO = hypobromous acid
H3PO4 = phosphoric acid
HClO4 = perchloric acid
HNO2 = nitrous acid
H2C2O4 = oxalic acid
H2S = hydrosulfuric acid
HIO3 = iodic acid
Organic Acids
Contain carbon
 Only one of the hydrogens is “acidic” and
dissociates in solution


Ex:
Acetic Acid
 HC2H3O2
or
CH3COOH
Naming Bases

Name them like any other ionic compound.

Name usually ends in “hydroxide”

Ex: LiOH = lithium hydroxide
Some Common Bases
See Table L
NaOH
sodium hydroxide
KOH
potassium hydroxide
Ba(OH)2
barium hydroxide
Mg(OH)2
magnesium hydroxide
Al(OH)3
aluminum hydroxide
18
Important Note

There are no “organic bases” (containing
carbon).
C2H5OH for example is not a base.
It is an alcohol. The OH on this molecule
does not dissociate to form OH- (hydroxide
ion)
Salts

“Salts” are ionic compounds that are not
acids or bases.
Metal cation (+) & nonmetal anion (-)
 They are electrolytes


Ex: NaCl, MgSO4, Li2S
Learning Check
Acid, Base
or Salt
Name
CaCl2
______
_______________
KOH
______
_______________
Ba(OH)2 ______
_______________
HBr
______
_______________
H2SO4
______
________________
21
Answers
Acid,Base
or Salt
Name
CaCl2
salt
calcium chloride
KOH
base
potassium hydroxide
Ba(OH)2
base
barium hydroxide
HBr
acid
hydrobromic acid
H2SO4
acid
sulfuric acid
Dissociation

Dissociation: when a compound splits
apart into ions in solution.
How might these dissociate?
H2SO4
KOH
Acids React with Metals

See Reference Table J


Metals above Hydrogen on the table will react
with acids to form a salt and H2 gas
Single Replacement Reaction
2Zn(s) + 2HCl(aq)
ZnCl2(aq) + H2(g)
Will an acid react with these metals?

If so complete and balance the single
replacement reaction.
Mg + HNO3
Cu + HCl
Ca + H2SO4
Answers
Mg + 2HNO3
Cu + HCl
Ca + H2SO4
Mg(NO3)2 + H2
No reaction Cu in below
hydrogen on Table J
Ca(SO4) + H2
Acid, Bases and Metals BBC (good for
Indicators)
 http://www.bbc.co.uk/schools/ks3bitesize/s
cience/chemical_material_behaviour/acids
_bases_metals/activity.shtml

Pure Water is Neutral
Self Ionization of Water: a small quantity of
water molecules in a sample will self ionize.
This results in a small, but equal amount of
H+ and OH-
H+
OH-
H2O
H+ + OH-
Hydrogen Ion = Hydroxide Ion
[H+] = [OH-]
Self Ionization of Water
http://youtu.be/kW-Zk4zABzw
Acids

Increase the H+ concentration

As H+ increases, OH- decreases
[H+] > [OH-]
H+
OH-
Bases

Increase the hydroxide ion (OH-)
concentration

When OH- increases, H+ decreases
[OH] > [H+]
H+
OH-
Important Summary
Acidic:
[H+] > [OH-]
Basic:
[H+] < [OH-]
Neutral: [H+] = [OH-]
Determining if it is an Acid or Base

How can you tell if something is acidic or
basic?

Use an electronic pH meter

Use an indicator such as
litmus

Use pH paper containing universal indicator
Acid/Bases Indicators
See Table M
Examples:
 Litmus



pH range for color change (4.5 – 8.3)
Color change: red to blue
Phenolphthalein


pH range for color change (8 - 9)
Color change: colorless to pink
What color would these be if the
pH = 10?
pH = 3?
pH Scale
0
1
2
3 4 5
6
7 8 9 10 11 12 13 14
Basic
Acidic
Neutral
[H+]>[OH-]
[H+] = [OH-]
[OH-]>[H+]
Pretty Hydrangeas

The color of hydrangea flowers depends
on the pH of the soil.
What is pH?

Tells us the relative quantity of H+ ions (or
the acidity) in solution.

The greater the [H+] the lower the pH.
Calculating pH
pH = - log [H+]
 From the French pouvoir hydrogene
(“hydrogen power” or power of
hydrogen)
[H+]
pH
1 x 10-5 M
5
1 x 10-9 M
9
1 x 10-11 M
11
43
Calculating pOH

What if you are given the concentration of
a base?

Ex: .000001M LiOH
You need to find the pOH!!
pOH
pOH = -log [OH-]
Ex:
.000001M LiOH = 1 x 10-6
pOH = 6
Ex:
.0001M NaOH = 1 x 10-4
pOH = 4
How can you find pH of a Base?

Easy!!!
pH + pOH = 14
Ex:
.000001M LiOH = 1 x 10-6
pOH = 6
pH = 8
Ex:
.0001M NaOH = 1 x 10-4
pOH = 4
pH = 10
Kw
If you know the concentration of one ion you
can find the other!
[H+] x [OH-] = 1 x 10-14
This is called the Kw
Or the “ion product” of water.

So what is the [OH-] is the [H+] is .001M?
[1 x 10-3] x [OH-] = 1 x 10-14
[OH-] = 1 x 10-11
Everything keeps adding up to 14!!
What’s up with that?
Let’s Try It
You have a .001 HCl solution.
Find: [H+], [OH-], pH, pOH
Let’s Try It
You have a .000000001M NaOH solution.
Find: [H+], [OH-], pH, pOH
Equation Summary
pH = -log [H+ ]
[H+ ] = 10-pH
pH + pOH = 14
pOH = -log [OH- ]
[OH- ] = 10-pOH
[H+ ] x [OH- ] = 1x10-14
Acidic solution:
Neutral solution:
Basic solution:
pH < 7 pOH > 7
pH = 7 pOH = 7
pH > 7 pOH < 7
pH and pOH game
 http://www.quia.com/rr/4051.html

Honors Questions
If the pH of a solution is 3.25 find the pOH,
[H+], and [OH-].
If .065 mole of KOH is placed in 20 liters of
water, what is the resulting pH?
Acid Rain
(Not to be confused with
“Chocolate Rain”)
Acid Rain

Unpolluted rain has
a pH of 5.6

It is naturally acidic
due to the gases in
the air that dissolve
in it.
Acid Rain

Rain with a pH
below 5.6 is “acid
rain“
pH of Rainwater
across United States in 2001
Sources of Acid Rain
Sources of Acid Rain

Power stations

Oil refineries

Coal with high S content

Car and truck emissions

Bacterial decomposition, and lightning
hitting N2

CO2 in the air forms carbonic acid
CO2 + H2O

H2CO3
This increases the [H+] of rain
H2CO3
H+ (aq) + HCO3-(aq)
 Reactions with oxygen in air form SO3
2SO2 + O2

2 SO3
Reactions with water in air form acids
SO3 + H2O
H2SO4 sulfuric acid
NO + H2O
HNO2 nitrous acid
HNO2 + H2O
HNO3 nitric acid
Effects of Acid Rain
Effects of Acid Rain

Leaches heavy metals like Al from soil,
which kills fish

Fish kills in spring from runoff due to
accumulation of large amounts of acid
in snow

Dissolves waxy coatings that protect
leaves from bacteria

Corrodes metals, textiles, paper and
leather
Acid Rain Destroys National Monuments
http://news.discovery.com/videos/earth-acidrain-eating-washington-dc.html
Global Warming: CO2 and Ocean Acidity
http://planetgreen.discovery.com/videos/blue
-august-acid-in-the-water.html
Acid Rain Site produced by EPA
 http://www.epa.gov/acidrain/education/site
_kids/

EPA Website Detailing Acid Rain Causes
and Effects as well as Legislation
 http://www.epa.gov/acidrain/

Neutralization
Reactions
General Reaction
Neutralization Forms Water
H+
from acid
+
OH-

from base
H 2O
neutral
This “net” reaction for neutralization is found
on Table I. It is an exothermic reaction.
Forming a Salt
(+) cation from the base,
(-) anion from the acid
combine to form a salt.
HCl + NaOH
NaCl + HOH
Acid + Base
Salt + water
Neutralization Reactions
These are double replacement reactions
Ions switch partners. Water is formed.
Neutralization Reactions
If equal concentrations of hydrogen ion H+ and
hydroxide ions OH- are mixed, it results in a
neutral solution.
Ex:
.1M LiOH +
.1M HCl =
Neutral Solution
Completing and Balancing and
Naming
Write charges for ions in acid and base.
 Switch ion partners. (+ ions stay in front!!)
 Do not bring over subscripts except if part
of a polyatomic ion!
 Criss-Cross charges to balance formulas.
 Balance entire equation.
 Name the acid, base and salt.

You Try It
Complete and balance formulas and
equation.
 Name acid base and salt

Ex: KOH + H2SO4
Ex: Mg(OH)2 + HNO3
Titrations
Purpose:
To determine the concentration of an acid
or base through a neutralization reaction.
Acid/Base Titration
Buret is filled with a
“standard solution” of
known concentration.
Erlenmeyer Flask contains
solution of unknown conc..
Indicator (phenolphthalein)
added to the flask.
Acid/Base Titrations
Slowly “titrate” or drip liquid
into flask from buret until
indicator changes color.
This is the “endpoint”.
Record total volume used
from buret.
Titration Formula
MA x VA = MB x VB
Molarity Acid x Volume Acid = Molarity Base x Volume Base
At “equivalence point”
Moles H+ = Moles OH-
Important Note

Multiply acid/base side of equation by
number of H+ or OH- ions it produces
when dissociating!!!

Ex:
H2SO4 produces 2 H+ so you would
multiply the acid side by “2”
You Try It!
A 50 ml sample of .2M HCl is neutralized by
75ml of NaOH. What is the conc. of the base?
HCl
NaOH
.2M x 50ml = MB x 75ml
MB = .13M
You Try It!
How much of a .1M H2SO4 solution is
needed to neutralize 50 ml of a .05 KOH
solution?
H2SO4
KOH
2 x .1M x VA = .05M x 50ml
VA = 12.5 ml
Titration Applet
http://group.chem.iastate.edu/Greenbowe/se
ctions/projectfolder/flashfiles/stoichiometry
/acid_base.html
Hydrolysis

Opposite reaction to neutralization
Salt + Water
Acid + Base
Parent Acid/Base

If you know the salt involved you should
be able to determine which acid and base
it would form if water is added.
Salt + Water
Acid + Base
Ex:
NaCl with water (HOH) would form HCl and NaOH
You Try It

Name the “parent” acid and base that
would be produced from these salts.

Ex:
Potassium chloride
Magnesium carbonate
pH and Hydrolysis

Salts can yield neutral, acidic or basic
solutions depending on what type of acid
or base they produce.
SA/SB = Neutral
SA/WB = Acidic
WA/SB = Basic
WA/WB = Undetermined
Strength of
Acids and Bases
Do they ionize 100%?
Strong Acids :
Give up H+ easily
Dissociate completely (100%) in water
HCl, HBr, HI, HNO3, H2SO4, HClO4, HClO3
Weak acids: (all others)
Hold onto H+
Few molecules dissociate
Ex: HC2H3O2
Let’s examine the behavior of
an acid, HA, in aqueous solution.
HA
What happens to the HA molecules in solution?
100% dissociation of HA
HA
H+
Strong Acid
AWould the
solution be
conductive?
Oh yeah…
Partial dissociation of HA
HA
H+
Weak Acid
AWould the
solution be
conductive?
Not really…
HA  H+ + A-
HA
H+
A-
Weak Acid
At any one
time, only a
fraction of
the molecules
are
dissociated.
Acids Ionizing in Water (Strong vs. Weak)
http://youtu.be/kcPjY9cQpWs
Acid H Transfer (Strong vs. Weak)
http://preparatorychemistry.com/acids_flashh
tm
Strong Bases: Dissociate completely (100%) in water
- Group I metal hydroxides (NaOH, LiOH, etc.)
- Some Group II metal hydroxides
Ca(OH)2, Ba(OH)2,
Sr(OH)2
Weak Bases
Only a few ions dissociate
Ex: NH 3 (ammonia)
Strength and Reactivity

Acids/bases of the same initial molar
concentration can react differently and conduct
electricity differently if one is weak and the other
strong.

Ex:
2M HCl =
Strong Acid,
very conductive
very reactive
2M HC2H3O2 = Weak Acid
Weak Conduction
Salad Dressing!!!
The Brønsted-Lowry Definition
of Acids and Bases
Acid:
PROTON DONOR
can donate H+ ions.
Base:
PROTON ACCEPTOR
accepts H+ ions.
Broader Definition than Arrhenius
Review: Arrhenius Definition of
Acids and Bases
 Acids produce H+ in aqueous (water) solutions
water
H+ (aq) + Cl- (aq)
HCl
 Bases produce OH- in aqueous (water) solutions
water
NaOH
Na+ (aq) + OH- (aq)
H+ Transfer
Acid/base reactions involve “proton transfer”.
The reaction need not occur in water.

H+ leaves one compound and is
transferred to another.
Ex: NH3 + H2O
Base
Acid
NH4+ + OH-
Conjugate acid/base pairs: formulas differ
by only a hydrogen ion, H+.
The acid on one side becomes the base on
the other side and vice versa.
Ex:
HCl + H2O
H3O+ + Cl-
Acid
Acid
Base
Base
Conjugate acid
contains one
more H+ in its
formula
Amphoteric/Amphiprotic Substances:
Can act as either an acid or a base.
Must have an “H” in formula (to donate)
Must have a free e- pair (to accept a H+)



Water is amphoteric
It can donate an H+
or accept an H+.
It depends on what it
is combined with.
Water donates H+
to NH3 forming the hydroxide ion (OH-).
Water accepts H+
from HCl forming the hydronium ion (H3O+).
When life goes either way
amphoteric (amphiprotic) substances
Acting like
a base
+
H+
H2CO3
accepts H+
HCO3-
Acting like
an acid
- H+
CO3-2
donates H+
Dilution
water (solvent)
solute
moles of solute remain constant
Vfinal
diluted, Mfinal
molesinitial = molesfinal
Vinitial
concentrated, Minitial
adding water lowers the solute concentration
Mfinal x Vfinal = Minitial x Vinitial
Titration Applet
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/stoichiometry/acid_base.htm
l
Strong/Weak Acid Animation
http://educypedia.karadimov.info/library/acid13.swf








Acid dissociation in water
http://www.chembio.uoguelph.ca/educmat/chm19104/chemtoons/chemtoons2.htm
Acid/Bases Theories
http://web.fccj.org/~ethall/acidbase/acidbase.htm
Titration Game
http://www.sciencegeek.net/Shockwave/Titration.htm
Acid Bases Hydrogen Transfer (Neutralization)
http://preparatorychemistry.com/neutralization_flash.htm