# 9.31     Amongst the following, the most stable complex is                 $(i)[Fe(H_{2}O_{6})]^{3+}$        $(ii)[Fe(NH_{3})_{6}]^{3+}$           $(iii)[Fe(C_{2}O_{4})_{3}]^{3-}$          $(iv)[FeCl_{6}]^{3-}$

We know that due to the chelation effect stability of the chelating compound is more than the simple compound.  Thus it is easy to notice that   $\dpi{100} [Fe(C_{2}O_{4})_{3}]^{3-}$ is most stable among all given compounds.