When $AgCl$ is treated with $KCN$,what happens?

Which of the following compounds after mixing cannot produce blue coloration?

Which of the following cations forms the least stable complex with the same ligand?

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?

Which equilibrium can be described as an acid-base reaction using the Lewis acid-base definition but not using the Bronsted-Lowry definition?

Copper sulphate solution reacts with $KCN$ to give