Which of the following is sparingly soluble in cold water and fairly soluble in hot water?

How do we differentiate between $Fe^{3+}$ and $Cr^{3+}$ in group $III$?

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

$A$ salt with a few drops of conc. $HCl$ gives an apple green colour in a flame test. The group precipitate of the salt is dissolved in acetic acid and treated with $K_{2}CrO_{4}$ to give a yellow precipitate. When the sodium carbonate extract of the salt solution is heated with conc. $HNO_{3}$ and ammonium molybdate,it results in a canary yellow precipitate. The cation and anion present in the salt are respectively,

Which reagents are used for the identification of Group $IV$ cations?

Nessler's reagent is