Elemental abundance in crust Si Al Fe Ca Na Mg K Ti H P - PDF document

CEE 680 Lecture #27 3/6/2020 Print version Lecture #27 Coordination Chemistry: Hydroxides & oxides (Stumm & Morgan, Chapt.6: pg.272 ‐ 275) Benjamin; Chapter 8.1 ‐ 8.6 David Reckhow CEE 680 #27 1  O Elemental abundance in crust  Si  Al  Fe  Ca  Na  Mg  K  Ti  H  P  Mn  F David Reckhow CEE 680 #2 2 1

CEE 680 Lecture #27 3/6/2020 Zinc  An essential metal  Needed for certain enzyme, e.g., alcohol dehydrogenase  Associate with a number of diseases  Only one oxidation state (+2)  Electrons: 3d 10 , 4s 2 (like Mg: 3s 2 )  Uses in plumbing  Galvanized steel/iron – coat of Zn protects from oxidation  Now mostly for mains and connections, not premise  Copper Alloys  Brass (Cu, Zn & <2% Pb),  Bronze (Cu, ~12% Sn, & others) David Reckhow CEE 680 #27 3 Hydrolysis  Metal accepts an electron from water and releases or repels a proton  Example: Zinc       First step Zn ( OH ) H *  K +2 = Zn(H 2 O) 5 OH + + H +  Zn(H 2 O) 6 1  2 [ Zn ]  Second step  Zn(H 2 O) 5 OH + = Zn(H 2 O) 4 (OH) 2 0 + H +    Zn ( OH ) [ H ]  * K 2 2  [ ZnOH ] David Reckhow CEE 680 #27 4 2

CEE 680 Lecture #27 3/6/2020 Hydrolysis (cont.)  Zinc example expressed as hydroxide formation  First step +2 + OH ‐ = Zn(H 2 O) 5 OH + + H 2 O  Zn(H 2 O) 6    Zn ( OH )  K 1  2  [ Zn ][ OH ]  Second step  Zn(H 2 O) 5 OH + + OH ‐ = Zn(H 2 O) 4 (OH) 2 0 + H 2 O   Zn ( OH )  K 2 2   [ ZnOH ][ OH ] David Reckhow CEE 680 #27 5 Hydrolysis (cont.)  Converting between the two forms    Zn ( OH ) +2 + OH - = Zn(H 2 O) 5 OH + + H 2 O  Zn(H 2 O) 6 K 1   2 [ Zn ][ OH ] H 2 O = H + + OH -    K w [ H ][ OH ]    +2 = Zn(H 2 O) 5 OH + + H + Zn(H 2 O) 6   Zn ( OH ) H *  K 1  2 [ Zn ]  K K 1 w David Reckhow CEE 680 #27 6 3

CEE 680 Lecture #27 3/6/2020 Cumulative stability constants   describes the equilibrium between any given complex and its component metal and ligands  is the product of the successive K’s   Zn ( OH )    K K 2 2 1 2   2 2 [ Zn ][ OH ]  Which describes the following equilibrium +2 + 2OH - = Zn(H 2 O) 4 (OH) 2 + 2H 2 O Zn(H 2 O) 6 David Reckhow CEE 680 #27 7 Cumulative stability constants (cont.)  And *  is the form of  which is in terms of H + , rather than OH ‐  is the product of the successive * K’s     2  Zn ( OH ) H    * * * K K 2 2 1 2  2 [ Zn ]  Which describes the following equilibrium +2 = Zn(H 2 O) 4 (OH) 2 + 2H + Zn(H 2 O) 6  And:   2 *    K 2 2 w David Reckhow CEE 680 #27 8 4

CEE 680 Lecture #27 3/6/2020 Cumulative stability constants (cont.)  So, in general:     ( n  m ) x m Me ( OH )     m K m x   n m [ Me ][ OH ]  x 1  And:    m    x  m ( n m ) Me ( OH ) H     * * K m m x  n [ Me ] x  1 David Reckhow CEE 680 #27 9  To next lecture David Reckhow CEE 680 #27 10 5