The oxidation state of chromium in the dimeric hydroxo-bridged complex $[(H_2O)_4Cr(OH)_2Cr(H_2O)_4]^{4+}$ is:

The oxidation state of cobalt in the complex $[Co(NH_3)_6]Cl_3$ is ........ .

$K_2[Zn(OH)_4]$ is the chemical formula for which coordination compound?

The $IUPAC$ name for the coordination compound $Ba[BrF_4]_2$ is

Specify the oxidation numbers of the metals in the following coordination entities:
$(i) [Co(H_{2}O)(CN)(en)_{2}]^{2+}$
$(ii) [CoBr_{2}(en)_{2}]^{+}$
$(iii) [PtCl_{4}]^{2-}$
$(iv) K_{3}[Fe(CN)_{6}]$
$(v) [Cr(NH_{3})_{3}Cl_{3}]$

Which of the following name-formula combinations is not correct?