Which of the following is a weak electrolyte in solution?

The active substance in Nessler's reagent used for the detection of ammonia is ..........

Some salts,although containing two different metallic elements,give a test for only one of them in solution. Such salts are:

What is the final product formed when copper sulphate solution reacts with excess $KCN$?

For the complex $ML_2$,the stepwise formation constants for the reactions:
$M + L \rightleftharpoons ML$
$ML + L \rightleftharpoons ML_2$
are $4$ and $3$ respectively. Hence,the overall stability constant for the reaction:
$M + 2L \rightleftharpoons ML_2$
is:

Aqueous ammonia readily dissolves $AgCl$ because