Silver chloride dissolves in

The cation that does not form an amine complex with excess of ammonia is

Given below are two statements: one is labelled as "Assertion $A$" and the other is labelled as "Reason $R$".
Assertion $A$: In the complexes $Ni(CO)_4$ and $Fe(CO)_5$,the metals have zero oxidation state.
Reason $R$: Low oxidation states are found when a complex has ligands capable of $\pi$-donor character in addition to the $\sigma$-bonding.
In the light of the above statements,choose the most appropriate answer from the options given below.

Identify the highest field strength ligand from the following.

The purple color of $KMnO_4$ is due to which of the following?

Copper sulphate solution reacts with $KCN$ to give