If an excess of $NH_4OH$ is added to a $CuSO_4$ solution,it forms a deep blue coloured complex which is:

The tendency to form complexes increases with ..........

$A$ solution containing $2.675 \ g$ of $CoCl_3 \cdot 6NH_3$ (molar mass $= 267.5 \ g \ mol^{-1}$) is passed through a cation exchanger. The chloride ions obtained in the solution are treated with excess $AgNO_3$ to give $4.78 \ g$ of $AgCl$ (molar mass $= 143.5 \ g \ mol^{-1}$). The formula of the complex is $(Ag = 108 \ u)$:

Violet colour of $[Ti(H_2O)_6]Cl_3$ on heating changes to $........$

$CN^{-}$ is a strong field ligand. This is due to the fact that

$CuSO_4$ reacts with $KCN$ solution and forms: