- Chem 31 3/12 Lecture Announcements The Chemistry Dept is trying to cut down on reports printed on Dept printers Other than data from instruments

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Chem. 31 – 3/12 Lecture
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Announcements The Chemistry Dept. is trying to cut down  on reports printed on Dept. printers.   Other than data from instruments, print  outs on yellow paper is not acceptable for  reports (e.g. Excel spreadsheets). Many constants are given in appendices  in the back of the text (K sp , K a , complex  ion formation constants)
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Complex Ions Example Reaction: Ag +    +  2NH 3 (aq)      Ag(NH 3 ) 2 + Metal      Ligand             Complex Ion Why does reaction occur? Metal is a Lewis acid (electron pair acceptor) NH 3  is a Lewis base (electron pair donator) Metal-ligand bonds are intermediate strength
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Complex Ions – Why Study? Useful in separations Complexed metals become  more organic soluble Effects on metal solubility (e.g. addition of NH 3  on AgCl  solubility) Complexometric titrations (e.g. water hardness titration) O O O O Na + Crown ether  (12-crown-4) Diethyl ether water Crown ether  added Sodium conc. given by  gray shading
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Complex Ions Step-wise vs. full reactions: Example: addition of NH 3  to Ag + Reaction occurs in steps: 1) Ag +   + NH 3 (aq)    AgNH 3 +                K 1  (=  β 1 ) 2) AgNH 3 + NH 3 (aq)   Ag(NH 3 ) 2 +      K 2 Net) Ag +    +  2NH 3 (aq)      Ag(NH 3 ) 2 +    β 2  = K 1 ∙K 2
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Complex Ions Due to commonly large exponents on ligand concentration,  a small change in ligand concentration has a big effect  on how metal exists Example: Al 3+  + 3C 2 O 4 2-    Al(C 2 O 4 ) 3 3-   β 3  = 4.0 x 10 15 [C 2 O 4 2- ] [Al(C 2 O 4 ) 3 3- ]/[Al 3+ ] 10 -4  M 4000 10 -5  M 4 10 -6  M 0.004
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This note was uploaded on 04/17/2008 for the course CHEM 31 taught by Professor Staff during the Spring '08 term at CSU Sacramento.

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- Chem 31 3/12 Lecture Announcements The Chemistry Dept is trying to cut down on reports printed on Dept printers Other than data from instruments

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