Gran Plot

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Gran Plot

• For HA ? H A-
• aH aA-
• aHA
• H ? H A- ? A-
• HA ? HA

Ka
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HA OH- ? H2O A-Formal HA FaFormal
NaOH Fb
In Buffer region A- mol OH- added
total volume FbVb
Va Vb mol HA mol HA init - mole
OH- added HA FaVa FbVb
Va Vb
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• H ? H Vb Fb ? A-
  pH -log aH
• ( FaVa FbVb ) ? HA
  or aH 10-pH
• rearranging gives
• ? HA Ka ( FaVa
  FbVb )
• At equivalence point, mol NaOH added mole HA
  initial, so
  Fb Ve Fa Va
• Or Ve FaVa

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Ka
Vb 10-pH
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? A-
Fb
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Fb
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• ? HA Ka (Ve Vb )
  Gran Plot
• is a linear equation y mx b
• y Vb 10-pH
• m ? HA Ka / ? A-
• x Vb
• b ? HA Ka Ve/ ? A-

Vb 10-pH
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? A-
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