pKa Concepts

pKa Concepts - For a weak acid, which dissociates as...

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1 See Sparks, 2003; Evangelou, 1998; or Essington, 2004 or http://www.khanacademy.org Assorted videos on acid-base, buffers, pKa, and Henderson- Hasselbalch eqn pKa concepts Ionization = the process in which ions are formed from neutral compounds; Dissociation = the separation of the ions of an electrovalent compound as a result of the action of a solvent (usually water) For a weak acid, which dissociates as follows: HA H + + A - An interesting and extremely useful relationship between pH and pK a can be obtained simply by taking logarithms (to the base 10) of the previous equation: log 10 K a = log 10 [H + ] + log 10 [A - ] - log 10 [HA] Rearranging: -log 10 [H + ] = -log 10 K a + log 10 [A - ] - log 10 [HA] Note: log a – log b = log (a/b); px = -log[x] giving the Henderson-Hasselbalch equation :
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2 Using pK a and pH relationship • By using pK a values, we are able to express the strength of an acid (i.e. its tendency to dissociate) with reference to the pH scale. • If K
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This note was uploaded on 10/20/2010 for the course SOIL 479 taught by Professor Ulery during the Spring '10 term at NMSU.

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pKa Concepts - For a weak acid, which dissociates as...

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