$[Ni(CO)_4]$ is diamagnetic. Which of the following statements is correct for this complex?

Write down the $IUPAC$ name for each of the following complexes and indicate the oxidation state,electronic configuration,and coordination number. Also,give the stereochemistry and magnetic moment of the complex:
$(i)$ $K[Cr(H_2O)_2(C_2O_4)_2] \cdot 3H_2O$
$(ii)$ $[Co(NH_3)_5Cl]Cl_2$
$(iii)$ $CrCl_3(py)_3$
$(iv)$ $Cs[FeCl_4]$
$(v)$ $K_4[Mn(CN)_6]$

$A$ mixture $X$ containing $0.02 \ mol$ of $[Co(NH_3)_5SO_4]Br$ and $0.02 \ mol$ of $[Co(NH_3)_5Br]SO_4$ was prepared in $2 \ L$ of solution.
$1 \ L$ of mixture $X +$ excess $AgNO_3 \to Y$.
$1 \ L$ of mixture $X +$ excess $BaCl_2 \to Z$.
The number of moles of $Y$ and $Z$ are:

Consider the following complexes:
$(a) \ Na_2[Fe(CN)_5NO]$
$(b) \ [Fe(H_2O)_5NO]SO_4$
$(c) \ K_4[Fe(CN)_6]$
Which of the following statements is wrong?

Match the following complexes in List-$I$ with their colors in List-$II$:

List-$I$ (Complex)	List-$II$ (Color)
$A. [Ni(en)_3]^{2+}$	$I. \text{Green}$
$B. [Ni(H_2O)_4(en)]^{2+}$	$II. \text{Blue}$
$C. [Ni(H_2O)_6]^{2+}$	$III. \text{Pale blue}$
$D. [Ni(H_2O)_2(en)_2]^{2+}$	$IV. \text{Violet}$

The sum of the total number of $Cr-O$ bonds in chromate $(CrO_4^{2-})$ and dichromate $(Cr_2O_7^{2-})$ ions is: