Conc. $HNO_3$ is added before proceeding to test for group $III$ members. This is to

$A$ solution of a metal ion,when treated with $KI$,gives a red precipitate which dissolves in excess $KI$ to give a colourless solution. Moreover,the solution of the metal ion,on treatment with a solution of cobalt$(II)$ thiocyanate,gives rise to a deep blue crystalline precipitate. The metal ion is:

Which of the following compounds changes the color of an aqueous $FeCl_3$ solution?

On saturating an aqueous solution of $Cu(II)$,$Pb(II)$,and $Zn(II)$ ions with $H_2S$,which of the following will precipitate?

Which radicals are precipitated by $(NH_4)_2CO_3$ in the presence of $NH_4OH$ (alkali)?

$A$ light greenish coloured salt was soluble in water. On passing $H_2S$ into the solution,a black precipitate was obtained which dissolved readily in $HCl$. The metal ion present is: