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

When $H_2S$ gas is passed through a hot acidic aqueous solution containing $Al^{3+}$,$Cu^{2+}$,$Pb^{2+}$ and $Ni^{2+}$,a precipitate is formed,which consists of

Which of the following is not precipitated as sulphide by passing $H_2S$ in the presence of concentrated $HCl$?

$A$ solution,when diluted with $H_2O$ and boiled,gives a white precipitate. On the addition of excess $NH_4Cl / NH_4OH$,the volume of the precipitate decreases,leaving behind a white gelatinous precipitate. Identify the precipitate which dissolves in $NH_4OH / NH_4Cl$.

In which of the following is lead sulfate $(PbSO_4)$ soluble?

$A$ $0.3 \, M$ $HCl$ solution contains the following ions: $Hg^{2+}, Cd^{2+}, Sr^{2+}, Fe^{2+}, Cu^{2+}$. The addition of $H_2S$ to the above solution will precipitate which of the following?