Cobalt$(III)$ chloride forms a green coloured complex '$X$' with $NH_3$. The number of moles of $AgCl$ formed when an excess of $AgNO_3$ solution is added to $100 \ mL$ of a $1 \ M$ solution of '$X$' is:

In which one of the following pairs of ions is there an ion that forms a coordination compound with both aqueous sodium hydroxide and ammonia,and another ion that forms a coordination compound only with aqueous sodium hydroxide?

Assertion : $[Al(H_2O)_6]^{3+}$ is a stronger acid than $[Mg(H_2O)_6]^{2+}$.
Reason : Size of $[Al(H_2O)_6]^{3+}$ is smaller than $[Mg(H_2O)_6]^{2+}$ and possesses more effective nuclear charge.

Cold ferrous sulphate solution on absorption of $NO$ develops brown colour due to the formation of

$FeSO_4$ solution mixed with $(NH_4)_2SO_4$ solution in $1:1$ molar ratio gives the test of $Fe^{2+}$ ion,but $CuSO_4$ solution mixed with aqueous ammonia in $1:4$ molar ratio does not give the test of $Cu^{2+}$ ion. Explain why?

In $[Fe(CO)_5]$,the $Fe-C$ bond has