Acids and Bases

1
Acids and Bases
Acids
Bases
OH-
H
Acid a substance that gives off H ions in
water.
Base a substance that gives off OH- ions in
water.
Svante Arrhenius 1859-1927
Init ltlt5/12/2008 by Daniel R. Barnes
WARNING This presentation includes a
combination of original graphical images created
by the author and images taken without specific
permission from the world wide web. Do not
distribute or copy this presentation.
2
Acids and Bases
Acids
Bases
OH-
H
H2O
Acid a substance that gives off H ions in
water.
Base a substance that gives off OH- ions in
water.
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BASE
ACID
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Acids and Bases
Acids
Bases
CH3(CH2)16COONa
H2SO4
H3PO4
NaHCO3
NaOH
CH3COOH
KOH
NH3
HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
5
Acids and Bases
Acids
Bases
hydronium ion
CH3(CH2)16COONa
H2SO4
H3PO4
NaHCO3
NaOH
CH3COOH
sulfuric acid
KOH
NH3
HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
H3O
STRONG

6
Dont be fooled by the H3.
H3PO4 is a strong molecule, so it is a weak
acid.
Acids and Bases
Acids
Bases
CH3(CH2)16COONa
H2SO4
H3PO4
phosphoric acid
NaHCO3
NaOH
CH3COOH
KOH
NH3
X
HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
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Acids and Bases
Acids
Bases
CH3(CH2)16COONa
H2SO4
acetic acid
H3PO4
NaHCO3
NaOH
CH3COOH
CH3COOH
KOH
NH3
HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
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Acids and Bases
Acids
Bases
CH3(CH2)16COONa
H2SO4
H3PO4
NaHCO3
NaOH
CH3COOH
KOH
NH3
HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
hydrochloric acid
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Acids and Bases
Acids
Bases
CH3(CH2)16COONa
H2SO4
H3PO4
NaHCO3
NaOH
CH3COOH
KOH
NH3
nitric acid
HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
721-815 AD
Abu Musa Jabir ibn Hayyan
10
O
Acids and Bases
Acids
Bases
H
H
O
C
O
O
O
H
CH3(CH2)16COONa
H2SO4
C
H3PO4
C
?
O
C
NaHCO3
?
NaOH
H
C
CH3COOH
C
?
O
H
KOH
NH3
H
H
H
citric acid
HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
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(No Transcript)
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Acids and Bases
Acids
Bases
sodium hydroxide
CH3(CH2)16COONa
H2SO4
H3PO4
NaHCO3
NaOH
CH3COOH
KOH
NH3
HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
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Acids and Bases
Acids
Bases
CH3(CH2)16COONa
sodium stearate
H2SO4
H3PO4
NaHCO3
NaOH
CH3COOH
KOH
NH3
HCl
HNO3
NH4OH
Ca(OH)2

HOOCCH2COH(COOH)CH2COOH
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NEUTRALIZATION
Acids and Bases
Acids
Bases
sodium hydrogen carbonate
CH3(CH2)16COONa
H2SO4
H3PO4
NaHCO3
NaOH
CH3COOH
KOH
NH3

HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
WATER
ACID
BASE
SALT
NaHCO3

CH3COOH
NaCH3COO CO2 H2O
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Acids and Bases
Acids
Bases
CH3(CH2)16COONa
H2SO4
H3PO4
NaHCO3
NaOH
ammonia
CH3COOH
KOH
NH3
HCl
HNO3
NH4OH
Ca(OH)2
ammonium hydroxide
HOOCCH2COH(COOH)CH2COOH
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Acids and Bases
Acids
Bases
CH3(CH2)16COONa
H2SO4
H3PO4
NaHCO3
NaOH
CH3COOH
KOH
NH3
HCl
HNO3
NH4OH
Ca(OH)2
HOOCCH2COH(COOH)CH2COOH
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Our notions of
Acids and Bases
Acids
Bases
(at least the older definitions of acid and
base)
are prejudiced by the fact that Earth is a mostly
water-covered planet
and, that, consequently, Earths creatures,
including people, are made mostly of water.
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Water molecules are very stable.
Nonetheless, every once in a while, a water
molecule breaks in two.
H2O
OH-
H

The hydrogen and hydroxide ions that water breaks
into like each other a lot because of their
opposite charges, so they get back together again
pretty fast.
Therefore, the equation for the dissociation of
water deserves a double arrow, since it is a
reversible reaction.
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Because water molecules rarely break, and because
they get back together again so quickly when they
do break, the amount of broken molecules in a
quantity of pure water is very low.
H2O
OH-
H

ltlt 1
gt 99.9
The percentages listed here are quite rough. We
can be even more precise if we want to.
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Because water molecules rarely break, and because
they get back together again so quickly when they
do dissociate, the amount of broken molecules in
a quantity of pure water is very low.
H2O
OH-
H

ltlt 1
gt 99.9
unbroken
broken
The percentages listed here are quite rough. We
can be even more precise if we want to.
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In pure water, the concentration of broken
water molecules is 10-7M
OH-
H

Thats the same thing as 10-7 mol/L
broken water
10-7 mol/L 0.0000001 mol/L
One liter (L) of water has a mass of 1000 g.
The molar mass of water is 18 g/mol.
(1000 g)/(18 g/mol) 55.6 mol, so the
concentration of water in water is 55.6 mol/L.
(55.6 mol/L)/(10-7 mol/L) 556,000,000
In pure water, only one out of every 556,000,000
water molecules is broken.
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H
OH-

BROKEN WATER
In pure water, only one out of every 556,000,000
water molecules is broken.
Thats about 0.002 ppm
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pH
7
0
14
24
pH
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Click the link below to an FDA web page listing
pHs of different foods.
pH

• http//vm.cfsan.fda.gov/comm/lacf-phs.html

According to this web page, what is the
overwhelming tendency for the pH of foods?
Acids
Foods tend to be . . .
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sour
neutral
bitter
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pH
. . . the esoteric version . . .
pH stands for potential hydrogen. (maybe)
pH is a weird, numerical way of showing the
hydrogen ion concentration in a solution.
Mathematically, pH -logH
Thats slightly confusing even if you know what
logs are.
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log(10n) n
logs
log(1000) 3
log(0.1) -1
log(10) 1
log(1) 0
log(1,000,000) 6
log(0.0001) - 4
log(100) 2
log(1013) 13
log(50) 1.6987. . .
log(10-5) -5
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pH
Lets give an example of pH normal water.
In normal water, the hydrogen ion concentration
is 10-7M.
In other words, H 10-7M.
Since pH -logH . . .
The pH of normal water would be 7.
30
pH
In sea water, however, the pH is 8.
What would the hydrogen ion concentration be in
sea water?
In sea water, H 10-8M.
Thats a little more basic than pure water.
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pH
H2SO4
Car batteries are filled with very dangerous
sulfuric acid.
In battery acid, one of the most corrosive acids
there is, the hydrogen ion concentration is
about 1M.
1 100, so . . .
In battery acid, the pH is . . .
0
32
pH
Lemon juice is one of the most acidic foods you
can eat.
In lemon juice, the hydrogen ion concentration is
about 10-2M.
2
In lemon juice, the pH is . . .
Thats not as strong as battery acid, but it can
still rot your teeth.
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pH
Sodium hydroxide is a strong base.
Its also known as lye and turns fat into soap,
which makes it a handy drain opener.
In a concentrated sodium hydroxide solution, the
hydrogen ion concentration can be about 10-14M.
In such a concentrated solution of sodium
hydroxide, the pH is . . .
14
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pH
A typical pH for vinegar is 3.
What would the hydrogen ion concentration be in
vinegar?
In vinegar, H 10-3M.
Thats not quite as acidic as lemon juice or
battery acid, but thats still pretty sour.
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High H
Low pH
H
Acids
Low H
High pH
36
High OH-
Low pOH
OH-
Low p 's High Concentrations
High p 's Low Concentrations
Bases
Low OH-
High pOH
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H2O
OH-
H

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Unless disturbed, aqueous (watery) systems, such
as a cup of water, an ocean, a car battery, or
your bloodstream, will tend reach a state of
equilibrium, in which the forward and reverse
reactions shown below occur at equal rates.
H2O
OH-
H

Equilibrium
when opposite processes occur at equal rates.
Amounts of different chemicals are probably not
equal to each other.
However, at equilibrium, the amount of each
chemical does not change as time goes by.
At equilibrium, water molecules fall apart but
they come back together again just as quickly as
they fall apart.
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LeChateliers Principle
H2O
OH-
H

If a system is at equilibrium, the amount of each
chemical will remain constant as time goes by.
However, if a system at equilibrium is disturbed
by some kind of stress, the reaction rates will
change in whatever way will oppose the effects of
the disturbance.
If a bunch of molecules are at equilibrium and
you disturb them, the molecules will try to undo
the work you have done.
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LeChateliers Principle
H2O
OH-
H

Imagine a bathtub full of water. If not
disturbed, it will reach an equilibrium with
regard to the above reversible reaction.
H 3
OH- 3
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LeChateliers Principle
H2O
OH-
H

However, if you raise the H, say, by pouring
in some hydrochloric acid, this will disturb the
equilibrium.
Didnt you see us being in equilibrium?
RUDE!
Sa-kurity!
Oh no you di-ent just add more H!
H 3
OH- 3
6
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LeChateliers Principle
H2O
OH-
H

The system will now do whatever it takes to lower
the H, to undo what you just did . . . at
least partially . . .
H 3
OH- 3
6
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LeChateliers Principle
H2O
OH-
H

The equilibrium, as they say, will shift to the
left. Why?
The forward reaction creates H, but the reverse
reaction (going to the left) uses up H, turning
it into water.
Did you notice that by adding H, you made OH-
decrease?
1
H 3
OH- 3
6
4
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It is generally true that if you make H
increase, you will cause a decrease in OH-.
This is expressed mathematically by the following
equation
HOH- 10-14M2
If two numbers always multiply to give the same
result, then when one of the two numbers gets
bigger, the other must get smaller. Take the
following example
1 x 24 24
2 x 12 24
3 x 8 24
4 x 6 24
6 x 4 24
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It is generally true that if you make H
increase, you will cause a decrease in OH-.
This is expressed mathematically by the following
equation
HOH- 10-14M2
Now try some acid-base examples. These examples
could be any aqueous (watery) system.
If H 10-3M, then OH- 10-11M
1 x 24 24
If H 10-12M, then OH- 10-2M
2 x 12 24
If H 10-1M, then OH- 10-13M
3 x 8 24
If H 10-7M, then OH- 10-7M
4 x 6 24
If H 1M, then OH- 10-14M
6 x 4 24
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It is generally true that if you make H
increase, you will cause a decrease in OH-.
This is expressed mathematically by the following
equation
HOH- 10-14M2
Now, just for fun and review, tell me the pH for
each of the following solutions, and tell me if
its acid, base, or neutral.
pH 3 (acid)
If H 10-3M, then OH- 10-11M
If H 10-12M, then OH- 10-2M
pH 12 (base)
If H 10-1M, then OH- 10-13M
pH 1 (acid)
If H 10-7M, then OH- 10-7M
pH 7 (neutral)
If H 1M, then OH- 10-14M
pH 0 (acid)
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pH
pH pOH 14
If the pH of a concentrated sodium hydroxide
solution is 14, Then the pOH is . . .
zero
High pOH
Low pH acid (ltlt 7)
pH of 7 neutral (like water)
Medium pOH
High pH base (gt7)
Low pOH
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High H or low H?
High OH- or low OH-?
High pH or low pH?
High pOH or low pOH?
H
H
Acid, base or neutral?
H
H
H
H
H
OH-
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High H or low H?
High OH- or low OH-?
High pH or low pH?
High pOH or low pOH?
H
H
Acid, base or neutral?
OH-
OH-
H
OH-
OH-
OH-
OH-
H
OH-
50
High H or low H?
medium
medium
High OH- or low OH-?
medium
7
High pH or low pH?
High pOH or low pOH?
medium
7
H
OH-
Acid, base or neutral?
OH-
H
OH-
H
OH-
H
OH-
H
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amino
acid
amino acid
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methyl
acid
formula?
C2H4O2
acetic acid
CH3COOH
ethanoic acid