The reaction of aqueous $[Ni(H_2O)_6]^{2+}$ is performed by the addition of a bidentate ligand ethane-$1,2$-diamine $(en)$. Match the following:

$[Ni(H_2O)_6]^{2+} : en$ molar ratio	Colour of the product
$A. 1:1$	$I. \text{Pale blue}$
$B. 1:2$	$II. \text{Blue/Purple}$
$C. 1:3$	$III. \text{Violet}$

The correct match is:

The reaction of $K_3[Fe(CN)_6]$ with freshly prepared $FeSO_4$ solution produces a dark blue precipitate called Turnbull's blue. The reaction of $K_4[Fe(CN)_6]$ with $FeSO_4$ solution in the complete absence of air produces a white precipitate $X$,which turns blue in air. Mixing the $FeSO_4$ solution with $NaNO_3$,followed by a slow addition of concentrated $H_2SO_4$ through the side of the test tube,produces a brown ring.
Precipitate $X$ is:
$(A)$ $Fe_4[Fe(CN)_6]_3$
$(B)$ $Fe[Fe(CN)_6]$
$(C)$ $K_2Fe[Fe(CN)_6]$
$(D)$ $KFe[Fe(CN)_6]$
Among the following,the brown ring is due to the formation of:
$(A)$ $[Fe(NO)_2(SO_4)_2]^{2-}$
$(B)$ $[Fe(NO)_2(H_2O)_4]^{3+}$
$(C)$ $[Fe(NO)_4(SO_4)_2]$
$(D)$ $[Fe(H_2O)_5(NO)]SO_4$

$A$ coordination compound has the formula $MCl_3 \cdot 4H_2O$. The coordination number of the metal is $6$,and it contains no water of hydration. How many $ml$ of $0.1 \, M \, AgNO_3$ are required to precipitate the chloride ions from $200 \, ml$ of a $0.01 \, M$ solution of this compound?

The colour of $CuCr_2O_7$ solution in water is green because

Which of the following orders is not correct?

Identify the correct set from the following table: