Urea reacts with water to form $A$ which will decompose to form $B$. $B$ when passed through $Cu^{2+}_{(aq)}$,a deep blue coloured solution $C$ is formed. What is the formula of $C$ from the following?

The number of moles of $NH_{3}$ that must be added to $2 \, L$ of $0.80 \, M \, AgNO_{3}$ in order to reduce the concentration of $Ag^{+}$ ions to $5.0 \times 10^{-8} \, M$ ($K_{\text{formation}}$ for $[Ag(NH_{3})_{2}]^{+} = 1.0 \times 10^{8}$) is ...... . (Nearest integer)
[Assume no volume change on adding $NH_{3}$ ]

Dimethyl glyoxime forms a coloured complex with

Which of the following ligands can form both high-spin and low-spin complexes?

Which compound is formed when an excess of $KCN$ is added to an aqueous solution of copper sulphate?

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