The reagent used for the identification of $Ni^{2+}$ ions is .....

On passing $H_2S$ gas,a black precipitate of $II$ group is obtained. The mixture may not contain:

When $H_2S$ gas is passed through an $HCl$ solution containing $CuCl_2, HgCl_2, BiCl_3$,and $CoCl_2$,which of the following will not precipitate?

Which one of the following statements is correct?

$A$ salt '$A$' which gives a green flame with a Bunsen burner,on reaction with dil. $H_2SO_4$ produces gas $(2)$ and white turbidity $(Z)$. The saturated solution of gas $(2)$ on reaction with $H_2S$ gas produces '$Z$'. Then select the $CORRECT$ statement.

An aqueous solution of a salt $X$ turns blood red on treatment with $CNS^{-}$ and blue on treatment with $K_4[Fe(CN)_6]$. $X$ also gives a positive chromyl chloride test. The salt $X$ is