Neutralization of Acids and Bases

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Neutralization of Acids and Bases
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• In general, a titration involves the addition of
  either a strong acid, strong base or both (must
  go to completion) as follows
• ACID BASE ?WATER SALT
• Titrations do not always yield an equivalence
  point with a pH of 7. Why?

Can further hydrolyze to form acidic or basic
solutions
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• Titrations

Burette
Standard Solution
Known Standard Solution
?
2nd titration
Sample Solution
Unknown Sample Solution
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Why a primary standard?

• If NaOH is the standard solution, its may
  not be accurate. Why?
• NaOH is hygroscopic (absorbs moisture in the air)
  which can affect its molar mass
• A primary standard is used to verify the of
  the known standard solution
• A primary standard must be
• Pure stable
• Non-hygroscopic
• Have an accurately known molar mass

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Choosing Indicators For Titrations
yellow
blue
will depend on the overall pH of the salt produced
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Strong Acids and Strong Base Titrations
Example HCl (strong acid) and NaOH (strong
base) Formula Equation___________________________
_______ Complete Ionic Equation
____________________________ Net Ionic
Equation__________________________________ pH at
equivalence point _____________________________ P
ossible Indicators_______________________________
___
HCl NaOH ? H2O NaCl
H Cl- Na OH- ? H2O Na Cl-
H OH- ? H2O
pH 7 (neutral salt)
Bromothymol blue
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Titration Curve for Strong Acid Strong Base
pH of sample solution is very low ?SA
Base is the standard solution being added
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Example CH3COOH (weak acid) and NaOH (strong
base)Formula Equation___________________________
_______Complete Ionic Equation
____________________________Net Ionic
Equation__________________________________pH at
equivalence point _____________________________P
ossible Indicators_______________________________
___
Weak Acids and Strong Base Titrations
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Weak Acid Strong Base
E.P gt 7
pH starts higher as CH3COOH is a weaker acid
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Weak Base and Strong Acid Titrations
Example NH3 (weak base) and HCl (strong
acid)Formula Equation___________________________
_______Complete Ionic Equation
____________________________Net Ionic
Equation__________________________________pH at
equivalence point _____________________________P
ossible Indicators_______________________________
___
11
Weak Base Strong Acid
Sample of Strong Base
E.P lt 7
Standard Acid is added
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Three types of Titrations
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Monoprotic Acids
When the mole ratio of acid to bases is 11 in
the balanced equation (assuming that the concns
are the same), then they will require equal
volumes to reach equivalence point
Acid and Base strength is irrelevant!!
Example A 0.2 M strong acid requires an equal
volume of 0.2 M weak base to reach equivalence
point if they have 11 ratio
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Polyprotic Acids
When an acid releases more than one proton, ie.
H2SO4, then they will require twice the volume
of base to reach equivalence point
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Titration of a polyprotic acidone equivalence
point per acidic hydrogen