Buffer Solutions

1
Buffer Solutions Buffer solutions are
equilibrium systems, which maintain a relatively
constant pH when small amounts of acids or bases
are added.
Acid Buffer Recipe Weak Acid Salt
(conjugate) HF NaF
Buffer Equation Same as weak acid   HF ? H
F-  
2
Buffer Solutions Buffer solutions are
equilibrium systems, which maintain a relatively
constant pH when small amounts of acids or bases
are added.
Acid Buffer Recipe Weak Acid Salt
(conjugate) HF NaF
Buffer Equation Same as weak acid   HF ? H
F-   High
3
Buffer Solutions Buffer solutions are
equilibrium systems, which maintain a relatively
constant pH when small amounts of acids or bases
are added.
Acid Buffer Recipe Weak Acid Salt
(conjugate) HF NaF
Buffer Equation Same as weak acid   HF ? H
F-   High low
4
Buffer Solutions Buffer solutions are
equilibrium systems, which maintain a relatively
constant pH when small amounts of acids or bases
are added.
Acid Buffer Recipe Weak Acid Salt
(conjugate) HF NaF
Buffer Equation Same as weak acid   HF ? H
F-   High low High
5
Buffer Equation Same as weak acid   HF ? H
F-   High low High
The HF is relatively high because HF is a weak
acid and does not dissociate very much. The H
is low for the same reason. The F- is high due
to adding the salt NaF to the solution. This
buffer solution has high concentrations of HF and
F-, which means it has the ability to shift left
or right and maintain the H concentration and
hence the pH remains at a relatively constant
level.
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1.0 M HCN is mixed with 2.0 M NaCN to make a
buffer solution. Write the equation for the
buffer solution. Determine the HCN and
CN-. HCN ? H CN-   1.0 M
7
1.0 M HCN is mixed with 2.0 M NaCN to make a
buffer solution. Write the equation for the
buffer solution. Determine the HCN and
CN-. HCN ? H CN-   1.0 M Low
8
1.0 M HCN is mixed with 2.0 M NaCN to make a
buffer solution. Write the equation for the
buffer solution. Determine the HCN and
CN-. HCN ? H CN-   1.0 M Low 2.0 M
9
Base Buffer Recipe Weak Base Salt
(conjugate) NH3 NH4Cl
Buffer Equation Same as weak base   NH3 H2O ? N
H4 OH-  
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Base Buffer Recipe Weak Base Salt
(conjugate) NH3 NH4Cl
Buffer Equation Same as weak base   NH3 H2O ? N
H4 OH-   High
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Base Buffer Recipe Weak Base Salt
(conjugate) NH3 NH4Cl
Buffer Equation Same as weak base   NH3 H2O ? N
H4 OH-   High High
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Base Buffer Recipe Weak Base Salt
(conjugate) NH3 NH4Cl
Buffer Equation Same as weak base   NH3 H2O ? N
H4 OH-   High High Low
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN  
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN N
aHCO3  
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3  
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4 NaH2PO4  
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4 NaH2PO4   KCH3COO  

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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4 NaH2PO4   CH3COOH KCH3CO
O  
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4 NaH2PO4   CH3COOH KCH3CO
O   NH4Cl
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4 NaH2PO4   CH3COOH KCH3CO
O   NH4Cl NH3
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4 NaH2PO4   CH3COOH KCH3CO
O   NH4Cl NH3   Na2CO3  
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4 NaH2PO4   CH3COOH KCH3CO
O   NH4Cl NH3   NaHCO3 Na2CO3  
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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4 NaH2PO4   CH3COOH KCH3CO
O   NH4Cl NH3   NaHCO3 Na2CO3   NaH2PO4

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Fill in the blanks to get buffer
solutions.   Acid Base   HCN   NaCN H2CO3
NaHCO3   H3PO4 NaH2PO4   CH3COOH KCH3CO
O   NH4Cl NH3   NaHCO3 Na2CO3   NaH2PO4
Na2HPO4
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  Buffer Application   1. Pick the two buffer
solutions   A. NH4Cl and HCl   B. NaCl and NaOH
  C. HF and NaF   D. NH4Cl and NH3            
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  Buffer Application   1. Pick the two buffer
solutions   A. NH4Cl and HCl   B. NaCl and NaOH
  C. HF and NaF   D. NH4Cl and NH3            
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  Buffer Application   1. Pick the two buffer
solutions   A. NH4Cl and HCl   B. NaCl and NaOH
  C. HF and NaF   D. NH4Cl and NH3 2. Write
the equations for the above two buffer solutions.
Label each species in the equation as high or
low concentration.      
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  Buffer Application   1. Pick the two buffer
solutions   A. NH4Cl and HCl   B. NaCl and NaOH
  C. HF and NaF   D. NH4Cl and NH3 2. Write
the equations for the above two buffer solutions.
Label the each species in the equation as high
or low concentration.      
HF ? H F-   NH3 H2O NH4 OH-
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  Buffer Application   1. Pick the two buffer
solutions   A. NH4Cl and HCl   B. NaCl and NaOH
  C. HF and NaF   D. NH4Cl and NH3 2. Write
the equations for the above two buffer solutions.
Label the each species in the equation as high
or low concentration.      
HF ? H F- High Low
High   NH3 H2O NH4 OH-
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  Buffer Application   1. Pick the two buffer
solutions   A. NH4Cl and HCl   B. NaCl and NaOH
  C. HF and NaF   D. NH4Cl and NH3 2. Write
the equations for the above two buffer solutions.
Label the each species in the equation as high
or low concentration.      
HF ? H F- High Low
High   NH3 H2O NH4 OH- High
High Low
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• A few drops of 0.10 M NaOH is added to a buffer
  solution at pH 5.00.
• The new pH could be
•  
• A 4.98
•  
• B. 5.02
•  
• C. 8.05
•  
• D. 2.11

34

• A few drops of 0.10 M NaOH is added to a buffer
  solution at pH 5.00.
• The new pH could be
•  
• A 4.98
•  
• B. 5.02
•  
• C. 8.05
•  
• D. 2.11

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Indicators Methyl violet HInd ? H Ind-  
Acid Base  
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue  
37
Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8  
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left  
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow  
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow HInd gt
Ind-  
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow HInd gt
Ind-   At pH gt 0.8
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow HInd gt
Ind-   At pH gt 0.8 Right
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow HInd gt
Ind-   At pH gt 0.8 Right Blue
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow HInd gt
Ind-   At pH gt 0.8 Right Blue HInd lt
Ind-
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow HInd gt
Ind-   At pH gt 0.8 Right Blue HInd lt
Ind- At pH 0.8
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow HInd gt
Ind-   At pH gt 0.8 Right Blue HInd lt
Ind- At pH 0.8 Middle
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow HInd gt
Ind-   At pH gt 0.8 Right Blue HInd lt
Ind- At pH 0.8 Middle Green
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Indicators Methyl violet HInd ? H Ind-  
Acid Base   Yellow Blue   Shift Co
lour   At pH lt 0.8 Left Yellow HInd gt
Ind-   At pH gt 0.8 Right Blue HInd lt
Ind- At pH 0.8 Middle Green HInd
Ind-
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  _at_ the transition point Ka
H   Ka 10-pH Ka 10-0.8 0.2