Identify the ligand with the highest field strength among the following.

Which among the following cations forms a least stable complex if the ligand is same?

Among the properties $(a)$ reducing,$(b)$ oxidising,$(c)$ complexing,the set of properties shown by $CN^{-}$ ion towards metal species is

Given below are two statements:
Statement $I$ : $N(CH_3)_3$ and $P(CH_3)_3$ can act as ligands to form transition metal complexes.
Statement $II$: As $N$ and $P$ are from same group,the nature of bonding of $N(CH_3)_3$ and $P(CH_3)_3$ is always same with transition metals.
In the light of the above statements,choose the most appropriate answer from the options given below:

In which of the following complexes is the radius of $Fe$ the largest?

Ammonia reacts with copper ions in a basic medium to form the complex ion $[Cu(NH_3)_4]^{2+}$,but it does not form this complex ion in an acidic solution. Why?