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

$A \xrightarrow{ K_4[Fe(CN)_6] } \text{Blue-white precipitate}$. Which ion is $A$?

Which mixture can be separated by a concentrated aqueous solution of sodium hydroxide $(NaOH)$?

Lead sulphate is soluble in:

$A$ pink coloured salt turns blue on heating. The presence of which cation is most likely?

$A$ is:
$\text{Salt } A \text{ (Colourless)} \xrightarrow{Cu} \text{Blue solution}$
$\text{Salt } A \text{ (Colourless)} \xrightarrow{HCl_{(aq)}} \text{White ppt}$
$\text{Salt } A \text{ (Colourless)} \xrightarrow{\text{Conc. } H_2SO_4} \text{Brown fumes}$