Transcript Reactions in Aqueous Solutions I

Reactions in Aqueous
Solutions I
1
Properties of Aqueous
Solutions of Acids & Bases
Acidic properties
 taste sour
 change the colors of indicators
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



turn litmus red
react with metals to generate H2(g)
react with carbonates and bicarbonates to
form salts, carbon dioxide and water
aqueous solutions conduct electricity
react with bases to produce salt and water
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Basic properties
 taste bitter
 feel slippery
 change colors of indicators


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turn litmus blue
SOAP
Properties of Aqueous
Solutions of Acids & Bases
react with acids to form salts and water
aqueous solutions conduct electricity
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Arrhenius Acid

Acid - A substance that produces
hydrogen ions, H+, in aqueous
solutions.
+
H
Cl
HCl 
+
+
HCN  H + CN
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Arrhenius Base
 Base
- A substance that produces
hydroxide, OH-, in aqueous
solutions.
+
K
OH
KOH 
+
+
NH3 + H2O  NH4 + OH
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Arrhenius Theory

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neutralization - combination of H+ (or
H3O+) with OHstrong acids - ionize 100% in water
HCl, HBr, HI, H2SO4, HNO3, HClO4

strong bases - ionize 100% in water
LiOH, NaOH, KOH, RbOH, CsOH,
Ca(OH)2, Sr(OH)2, Ba(OH)2
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Arrhenius Theory

total ionic equation for strong acid with
strong base
H aq   Cl aq   Na aq   OH -aq   Na aq   Cl -aq   H 2O(l)
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Arrhenius Theory

net ionic equation for strong acid with
strong base

aq
H
aq
 OH
 H2O(l)
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Acid-Base Theories

The most general theory for common
aqueous acids and bases is the
BRØNSTED - LOWRY theory
ACIDS DONATE
IONS
+
 BASES ACCEPT H IONS

+
H
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Acid-Base Theories
ACIDS DONATE H+ IONS
 BASES ACCEPT H+ IONS

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Brønsted-Lowry Acid-Base
Theory

differences between Arrhenius &
Brønsted-Lowry theories
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reaction does not have to occur in an
aqueous solution
bases do not have to be hydroxides
for example- ammonia is not a
hydroxide
NH3 + H2O  NH4+ + OH-
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Hydronium Ion

The hydrated hydrogen ion or
hydronium ion gives aqueous solutions
of acids their characteristic acidic
properties.
H2O + H+

H3O+
hydronium ion
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Hydrated Hydrogen Ion

H+(aq) is really H(H2O)n+


n is a small integer = 7?
H3O+ is usually used where n = 1
+

H3O
+
H
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Acid-Base Characteristics
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Solution Type
Acid
[H+ ]
Neutral [H+ ]
Base
[H+ ]
Relationship
>
[OH-]
=
[OH-]
<
[OH-]
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Brønsted–Lowry Acids

An acid is a proton donor.
HNO3 + H2O  H3O+ + NO3-
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Brønsted–Lowry Bases

A base is a proton acceptor.
NH3 + H2O  NH4+ + OH-
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Brønsted–Lowry Acids and
Bases

The Brønsted definition means NH3 is a
BASE in water — and water is itself an
ACID.
NH3
Base
+ H 2O
Acid
NH4+ + OH Acid
Base
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Brønsted–Lowry Acids and
Bases

An acid–base reaction is the transfer of
a proton from an acid to a base.
HCl + H2O  H3O+ + Clacid1
base2
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Brønsted–Lowry Acids and
Bases

When an acid
gives up a proton,
a conjugate base
is formed that is
capable of
accepting a
proton.
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Brønsted–Lowry Acids and
Bases
HF + H2O  H3O+ + Facid1
base2
acid2
base1
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Conjugate Acid-Bases

Conjugate acidbase pairs are a
reactant and a
product that differ
by a proton, H+.
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Conjugate Acid-Bases

Conjugate acid-base pairs are a
reactant and a product that differ by a
proton, H+.
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Conjugate Acid-Bases

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Every acid has a conjugate base,
formed by the removal of a proton from
the acid.
Every base has a conjugate acid
associated with it, formed by the
addition of a proton to the base.
Thus H3O+ is the conjugate acid of H2O.
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Conjugate Acid-Bases
HNO2 + H2O
Acid
Base

H3O+ + NO2-
Conjugate
Conjugate
acid base
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Conjugate Acid-Bases
NH3 + H2O
Base
Acid

NH4+ + OH-
Conjugate
Conjugate
acid base
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Conjugate Acid–Base
Strengths
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The more readily a substance gives up
a proton, the less readily its conjugate
base accepts a proton.
The more readily a base accepts a
proton, the less readily its conjugate
acid gives up a proton.
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Conjugate Acid–Base
Strengths

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The stronger an acid, the weaker its
conjugate base.
The weaker an acid, the stronger its
conjugate base.
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Conjugate Acid–Base
Strengths
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Ampholytes

A substance capable of being an acid or
a base is amphoteric.
H2O + H2O
acid1
base2
 H3O+ + OHacid2
base1
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Bronsted-Lowry Acid-Base
Theory
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water can be either an acid or base in
Bronsted-Lowry theory
amphoteric - species that can be either
an acid or base
amphiprotic - proton transfer reactions
that species behave as either an acid or
base


H 2O  H 2O 
H 3O  OH
base 1
acid 1
acid 2
base 2
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