Which of the following has the highest molar conductivity in solution?

Choose the correct statements from the following:
$A$. Ethane$-1, 2-$diamine is a chelating ligand.
$B$. Metallic aluminium is produced by electrolysis of aluminium oxide in the presence of cryolite.
$C$. Cyanide ion is used as a ligand for the leaching of silver.
$D$. Phosphine acts as a ligand in Wilkinson's catalyst.
$E$. The stability constants of $Ca^{2+}$ and $Mg^{2+}$ are similar with $EDTA$ complexes.
Choose the correct answer from the options given below:

Which of the following ions is the most stable?

Which of the following is a weak electrolyte in solution?

$Ni^{2+}$ ion can be estimated by using dimethyl glyoxime and forms a cherry-red precipitate. The complex is stabilized by

On adding excess of ammonium hydroxide to a copper chloride solution: