ACIDS AND BASES

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ACIDS AND BASES
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• Properties of Acids, Bases and, Salts
• Acids Bases Salts
• Taste
• Indicators
• (litmus)
• Conducts
• electricity
• Reacts with
• pH
• other

sour
salty
bitter
red
blue
x
yes
yes
yes
Some metals
x
Fats oils
lt 7
gt 7
?
Feels slippery
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• Electrolytes
• A substance that conducts an electrical current
  in an aqueous solution.

• 3 Classes Acids, Bases, and Salts

• When placed in water an electrolyte dissociates
  (acids/salts) or ionizes (bases) to form ions.
  These ions cause the solution to conduct an
  electrical current.

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• II. Nature of Acids and Bases
• Arrenhius (after observing conductivity)
  suggested that acid dissociates into H (hydrogen
  ions) in water.
• HCl ? H Cl-

B. Arrenhius suggested that bases ionizes into
OH- (hydroxide ions) in water. NaOH ?
Na OH-
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• Actual observation indicates that H exists
  in a hydrated form.
• (H3O, H5O2, H9O4, etc.)

D. H3O is the most common hydrated ion and is
called the _______________
Hydronium ion
E. HCl H2O ? H3O Cl-
HCl ? H Cl- ( the H3O
is often written as H)
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• Br?nsted-Lowry Acid Base Theory
• A. Proposed that acids are proton donors and
  bases are proton acceptors.

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HCl H2O ? H3O Cl- proton
proton conjugate conjugate ______
______ ________ ________ NH3
H2O ? NH4 OH- proton proton
conjugate conjugate ______
______ ________ ________

• products are referred to as conjugates.
• Each acid produces a conjugate base
• Each base produces a conjugate acid

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Amphoteric substances are capable of acting as
either an acid or a base, such as water.
The Br?nsted-Lowry theory also applies to
reactions that do not occur in aqueous
solutions. HCl(aq) NH3 (aq) ? Cl-
(aq) NH4 (aq) OR HCl(g) NH3(g) ?
NH4Cl(s)
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Lewis Acids and Bases
Lewis acids are electron pair acceptors.
Lewis bases are electron pair donors.
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Naming Acids (review)
Hydrobromic acid Carbonic acid Sulfuric
acid Nitrous acid Hydrochloric acid
HBr
H2CO3
H2SO4
HNO2
HCl
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Remembering from the Equations Unit

• Metal oxides added to water form bases
• (Metal oxides are also known as basic
• anhydrides)
• Na2O H2O NaOH

• Nonmetal oxides added to water form acids
• (Nonmetal oxides are also known as acidic
• anhydrides) CO2 H2O H2CO3

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• VII. Relative Strengths of Acids and Bases
• A. Strong Acids and Bases
• Ionize essentially 100 in water therefore, the
  reaction goes to completion and no equilibrium is
  established.
• (Since strong acids and bases ionize
  completely, their pH and pOH values are easily
  calculated since the H and OH- can be
  quickly determined by stoichiometry)

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• Weak Acids and Bases
• 1. Only ionize partially in water equilibrium
  established between ionized and unionized forms.
• HX ? H X- Ka HX-
• 
  HX
• JOH ? J OH- Kb JOH-
• JOH

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2. When given Ka , it is possible to calculate
H and therefore the pH pf the solution.
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Strong Acids are HCl HBr HI HNO3 HClO3 H2SO4
HClO4
Strong Bases are Ba(OH)2 Ca(OH)2 Sr(OH)2 NaOH
LiOH CsOH KOH RbOH
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IV. Autoionization of Water and the pH Scale A.
Water tends to spontaneously ionize by itself to
a very small extent. H2O H2O
H3O OH- (The reaction reverses
rapidly so that no one molecule remains ionized
for more than a fraction of a second. But, on
average, a proton transfers from one molecule to
the next at the rate of about 1000 x per second.)
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pH Scale pH -logH If H 1.0
x 10-7 If H 3.0 x 10-5 If H 4.7
x 10-11
pH 7 neutral
pH 4.5 acid
pH 10.3 base
pH scale pH lt 7 acid pH gt 7 base pH
7 neutral
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In a neutral solution H OH- ,
therefore H and OH- are the same value
______M If H ___ OH- acidic If H
___ OH- basic If H ___ OH- neutral
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pOH -logOH1-
OH1- 1x10-7 pOH 7 neutral
OH1- 1 x 10-5 pOH 5 base
OH1- 8 x 10-10 pOH 9.1 acid
pOH scale pOH lt 7 base pOH gt
7 acid pOH 7 neutral
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Other useful formulae pH pOH pKw
14 H 10-pH or OH- 10-pOH
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H OH-1
pH pOH
Kw H x OH-

-logOH-
10-pOH
-logH
10-pH
pH pOH 14
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• Measuring pH
• Indicators colored substances, usually derived
  from plants material, that can exist in either an
  acid or base form of different colors.
• usually in a liquid form or are impregnated in
  paper or tape such as litmus.
• Is there a single best indicator?