Transcript Making a Buffer Solution

Making a Buffer Solution: I
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Make a solution of a weak acid
• e.g., HCH3CO2, or acetic acid (HAc for short)
This solution counteracts the effect of a strong base by donating protons to
the basic compound, forming water and preventing pH change
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+
=>
OH-
HAc
Aqueous acetic acid
(Ka = 1.8*10-5)
Ac-
H2O
Final Solution
Strong Base (OH-)
Effect of Strong Base
Is Neutralized
(Virtually no H3O+ ions) )
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Making a Buffer Solution: II
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Make a solution of Sodium Acetate (NaCH3CO2)
The conjugate base of Acetic Acid is formed (CH3CO2-, the “acetate ion”; Ac for
short)
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• The metal ion Na+ is a “spectator ion” and irrelevant to this chemistry
This solution counteracts the effect of a strong base by donating protons to
the basic compound, forming water and preventing pH change
• The chlorine ion is irrelevant to this chemistry
+
=>
+
Ac-
Aqueous CH3CO2 -
HCl
Strong Acid (HCl)
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Cl-
Final Solution
(Cl ions irrelevant)
(Na ion not shown)
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HAc
=
Making a Buffer Solution: III
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A buffer is just a combination of the two solutions (weak acid plus its
conjugate base)
It combines the properties of these two solutions
• Neutralizes both strong acids and bases
Combine
Aqueous HAc (Ka = 1.8*10-5)
(Virtually no H3O+ ions) )
Conjugate Base (Ac-)
Buffer Solution
Weak Acid, Conjugate Base Coexist in Solution
(Na irrelevant, not shown)
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