# 12.11: Formation Constants for Complex Ions


Equilibrium Kf
${\text{Al}}^{\text{3+}}\text{+}6{\text{F}}^{-}\rightleftharpoons{\left[{\text{AlF}}_{6}\right]}^{\text{3-}}$ $7\times{10}^{19}$
${\text{Cd}}^{\text{2+}}\text{+}4{\text{NH}}_{3}\rightleftharpoons{\left[\text{Cd}{\left({\text{NH}}_{3}\right)}_{4}\right]}^{\text{2}\text{+}}$ $1.3\times{10}^{7}$
${\text{Cd}}^{\text{2+}}+4{\text{CN}}^{-}\rightleftharpoons{\left[\text{Cd}{\left(\text{CN}\right)}_{4}\right]}^{2-}$ $3\times{10}^{18}$
${\text{Co}}^{\text{2+}}+6{\text{NH}}_{3}\rightleftharpoons{\left[\text{Co}{\left({\text{NH}}_{3}\right)}_{6}\right]}^{2+}$ $1.3\times{10}^{5}$
${\text{Co}}^{\text{3+}}+6{\text{NH}}_{3}\rightleftharpoons{\left[\text{Co}{\left({\text{NH}}_{3}\right)}_{6}\right]}^{\text{3+}}$ $2.3\times{10}^{33}$
${\text{Cu}}^{+}+2\text{CN}\rightleftharpoons{\left[\text{Cu}{\left(\text{CN}\right)}_{2}\right]}^{-}$ $1.0\times{10}^{16}$
${\text{Cu}}^{\text{2+}}+4{\text{NH}}_{3}\rightleftharpoons{\left[\text{Cu}{\left({\text{NH}}_{3}\right)}_{4}\right]}^{\text{2+}}$ $1.7\times{10}^{13}$
${\text{Fe}}^{\text{2+}}+6{\text{CN}}^{-}\rightleftharpoons{\left[\text{Fe}{\left(\text{CN}\right)}_{6}\right]}^{4-}$ $1.5\times{10}^{35}$
${\text{Fe}}^{\text{3+}}+6{\text{CN}}^{-}\rightleftharpoons{\left[\text{Fe}{\left(\text{CN}\right)}_{6}\right]}^{3-}$ $2\times{10}^{43}$
${\text{Fe}}^{\text{3+}}+6{\text{SCN}}^{-}\rightleftharpoons{\left[\text{Fe}{\left(\text{SCN}\right)}_{6}\right]}^{3-}$ $3.2\times{10}^{3}$
${\text{Hg}}^{\text{2+}}+4{\text{Cl}}^{-}\rightleftharpoons{\left[{\text{HgCl}}_{4}\right]}^{2-}$ $1.1\times{10}^{16}$
${\text{Ni}}^{\text{2+}}+6{\text{NH}}_{3}\rightleftharpoons{\left[\text{Ni}{\left({\text{NH}}_{3}\right)}_{6}\right]}^{\text{2+}}$ $2.0\times{10}^{8}$
${\text{Ag}}^{+}+2{\text{Cl}}^{-}\rightleftharpoons{\left[{\text{AgCl}}_{2}\right]}^{-}$ $1.8\times{10}^{5}$
${\text{Ag}}^{+}+2{\text{CN}}^{-}\rightleftharpoons{\left[\text{Ag}{\left(\text{CN}\right)}_{2}\right]}^{-}$ $1\times{10}^{21}$
${\text{Ag}}^{+}+2{\text{NH}}_{3}\rightleftharpoons{\left[\text{Ag}{\left({\text{NH}}_{3}\right)}_{2}\right]}^{+}$ $1.7\times{10}^{7}$
${\text{Zn}}^{\text{2+}}+4{\text{CN}}^{-}\rightleftharpoons{\left[\text{Zn}{\left(\text{CN}\right)}_{4}\right]}^{2-}$ $2.1\times{10}^{19}$
${\text{Zn}}^{\text{2+}}+4{\text{OH}}^{-}\rightleftharpoons{\left[\text{Zn}{\left(\text{OH}\right)}_{4}\right]}^{2-}$ $2\times{10}^{15}$
${\text{Fe}}^{\text{3+}}+{\text{SCN}}^{-}\rightleftharpoons{\left[\text{Fe}\left(\text{SCN}\right)\right]}^{\text{2+}}$ $8.9\times{10}^{2}$
${\text{Ag}}^{+}+4{\text{SCN}}^{-}\rightleftharpoons{\left[\text{Ag}{\left(\text{SCN}\right)}_{4}\right]}^{3-}$ $1.2\times{10}^{10}$
${\text{Pb}}^{\text{2+}}+4{\text{I}}^{-}\rightleftharpoons{\left[{\text{PbI}}_{4}\right]}^{2-}$ $3.0\times{10}^{4}$
${\text{Pt}}^{\text{2+}}+4{\text{Cl}}^{-}\rightleftharpoons{\left[{\text{PtCl}}_{4}\right]}^{2-}$ $1\times{10}^{16}$
${\text{Cu}}^{\text{2+}}+4\text{CN}\rightleftharpoons{\left[\text{Cu}{\left(\text{CN}\right)}_{4}\right]}^{2-}$ $1.0\times{10}^{25}$
${\text{Co}}^{\text{2+}}+4{\text{SCN}}^{-}\rightleftharpoons{\left[\text{Co}{\left(\text{SCN}\right)}_{4}\right]}^{2-}$ $1\times{10}^{3}$