Chapter 16 Text
Chapter 16 Text
Chapter 16 Text
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<strong>16</strong>.8 Relationship Between Ka and Kb 639<br />
<strong>16</strong>.8 Relationship Between Ka and Kt b<br />
VVe've seen in a qualitative way that the stronger acids have the weaker conjugate<br />
bases. To see if we can find a corresponding quantitative relationship, let's<br />
consider the NH4+ and NH3 conjugate acid-base pair. Each of these species reacts<br />
with water:<br />
'(aq) ^=± NH3(flt|) + H+(aq) [<strong>16</strong>.38]<br />
H2O(0 ^=^ NH4+(ag) + OH~(aq) [<strong>16</strong>.39]<br />
Each of these equilibria is expressed by a characteristic dissociation constant:<br />
[NH3][H+]<br />
[NH4+]<br />
[NH4+][OH1<br />
[NH3]<br />
When Equations <strong>16</strong>.38 and <strong>16</strong>.39 are added together, the NH4+ and NH3 species<br />
cancel and we are left with just the autoionization of water.<br />
NH3(fl