The deep blue colour produced on adding excess of ammonia to copper sulphate is due to the presence of:

$AgNO_3 \xrightarrow{\Delta} (W) + (X) + O_2$
$(X) + H_2O \longrightarrow HNO_2 + HNO_3$
$(W) + HNO_3 \longrightarrow Y + NO + H_2O$
$(Y) + Na_2S_2O_3(\text{excess}) \longrightarrow (Z) + NaNO_3$
Identify $(W)$ to $(Z)$.

The correct increasing order of stability of the complexes based on $\Delta_o$ value is $:$
$I. \ [Mn(CN)_6]^{3-}$
$II. \ [Co(CN)_6]^{4-}$
$III. \ [Fe(CN)_6]^{4-}$
$IV. \ [Fe(CN)_6]^{3-}$

$A$ first row transition metal $(M)$ does not liberate $H_{2}$ gas from dilute $HCl$. $1 \ mol$ of aqueous solution of $MSO_{4}$ is treated with excess of aqueous $KCN$ and then $H_{2}S_{(g)}$ is passed through the solution. The amount of $MS$ (metal sulphide) formed from the above reaction is . . . . . . $mol$.

The solubility of silver bromide in hypo solution is due to the formation of

Which of the following complexes is the most stable?