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-

 

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]

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]

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]

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.

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

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

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

Base Buffer Recipe

Weak Base + Salt (conjugate)

NH3 NH4Cl

Buffer Equation Same as weak base

 

NH3 + H2O ⇋ NH4+ + OH-

 

Base Buffer Recipe

Weak Base + Salt (conjugate)

NH3 NH4Cl

Buffer Equation Same as weak base

 

NH3 + H2O ⇋ NH4+ + OH-

 

[High]

Base Buffer Recipe

Weak Base + Salt (conjugate)

NH3 NH4Cl

Buffer Equation Same as weak base

 

NH3 + H2O ⇋ NH4+ + OH-

 

[High] [High]

Base Buffer Recipe

Weak Base + Salt (conjugate)

NH3 NH4Cl

Buffer Equation Same as weak base

 

NH3 + H2O ⇋ NH4+ + OH-

 

[High] [High] [Low]

Fill in the blanks to get buffer solutions. Acid Base HCN  

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

NaHCO3

 

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4 NaH2PO4

 

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4 NaH2PO4

 KCH3COO

 

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4 NaH2PO4

 CH3COOH KCH3COO

 

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4 NaH2PO4

 CH3COOH KCH3COO

 NH4Cl

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4 NaH2PO4

 CH3COOH KCH3COO

 NH4Cl NH3

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4 NaH2PO4

 CH3COOH KCH3COO

 NH4Cl NH3

 Na2CO3

 

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4 NaH2PO4

 CH3COOH KCH3COO

 NH4Cl NH3

 NaHCO3 Na2CO3

 

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4 NaH2PO4

 CH3COOH KCH3COO

 NH4Cl NH3

 NaHCO3 Na2CO3

 NaH2PO4

Fill in the blanks to get buffer solutions. Acid Base HCN   NaCN

H2CO3 NaHCO3

 H3PO4 NaH2PO4

 CH3COOH KCH3COO

 NH4Cl NH3

 NaHCO3 Na2CO3

 NaH2PO4 Na2HPO4

 Buffer Application

 1. Pick the two buffer solutions 

A. NH4Cl and HCl

 B. NaCl and NaOH

 C. HF and NaF

 D. NH4Cl and NH3

  

    

 Buffer Application

 1. Pick the two buffer solutions 

A. NH4Cl and HCl

 B. NaCl and NaOH

 C. HF and NaF

 D. NH4Cl and NH3

  

    

 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.

   

 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-

 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-

 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]

3. 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

3. 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

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8  

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left 

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow 

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow [HInd] > [Ind-] 

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow [HInd] > [Ind-] At pH > 0.8

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow [HInd] > [Ind-] At pH > 0.8 Right

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow [HInd] > [Ind-] At pH > 0.8 Right Blue

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow [HInd] > [Ind-] At pH > 0.8 Right Blue [HInd] < [Ind-]

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow [HInd] > [Ind-] At pH > 0.8 Right Blue [HInd] < [Ind-]

At pH = 0.8

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow [HInd] > [Ind-] At pH > 0.8 Right Blue [HInd] < [Ind-]

At pH = 0.8 Middle

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow [HInd] > [Ind-] At pH > 0.8 Right Blue [HInd] < [Ind-]

At pH = 0.8 Middle Green

Indicators

Methyl violet HInd ⇋ H+ + Ind-

 Acid Base

 Yellow Blue

 Shift Colour

 At pH < 0.8 Left Yellow [HInd] > [Ind-] At pH > 0.8 Right Blue [HInd] < [Ind-]

At pH = 0.8 Middle Green [HInd] = [Ind-]

 

@ the transition point

Ka = [H+] 

Ka = 10-pH

Ka = 10-0.8

= 0.2