In the analysis of basic radicals,the group reagent $H_2S$ gas is generally used in which groups?

Which of the following statement$(s)$ is/are correct with reference to $Fe^{2+}$ and $Fe^{3+}$ ions?
$(1)$ $Fe^{3+}$ gives brown colour with potassium ferricyanide
$(2)$ $Fe^{2+}$ gives blue colour with potassium ferricyanide
$(3)$ $Fe^{3+}$ gives red colour with potassium thiocyanate
$(4)$ $Fe^{2+}$ gives brown colour with ammonium thiocyanate

Which of the following does not give a precipitate with $CrO_4^{2-}$?

Lead sulphate is soluble in:

Which reagent is used to test for the presence of the $Fe^{+2}$ ion?

Yellow ammonium sulphide solution is a suitable reagent for the separation of