Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$(NH_4)_2SO_4 + Sr(OH)_2 \longrightarrow SrSO_4 \downarrow + 2NH_3 \uparrow + 2H_2O$

Addition of $SnCl_2$ to $HgCl_2$ gives a precipitate of which color?

$A$ metal nitrate reacts with $KI$ to give a black precipitate which on addition of excess of $KI$ converts into an orange-colored solution. The cation of the metal nitrate is

Choose the correct tests with respective observations.
$(A)$ $CuSO_4$ (acidified with acetic acid) $+$ $K_4[Fe(CN)_6]$ $\rightarrow$ Chocolate brown precipitate.
$(B)$ $FeCl_3 + K_4[Fe(CN)_6]$ $\rightarrow$ Prussian blue precipitate.
$(C)$ $ZnCl_2 + K_4[Fe(CN)_6]$,neutralised with $NH_4OH$ $\rightarrow$ White or bluish white precipitate.
$(D)$ $MgCl_2 + K_4[Fe(CN)_6]$ $\rightarrow$ Blue precipitate.
$(E)$ $BaCl_2 + K_4[Fe(CN)_6]$,neutralised with $NaOH$ $\rightarrow$ White precipitate.
Choose the correct answer from the options given below:

Which compound is used to distinguish between $Fe^{2+}$ and $Fe^{3+}$ ions?

An inorganic compound $X$ on treatment with concentrated $H_{2}SO_{4}$ produces brown fumes and gives a dark brown ring with $FeSO_{4}$ in the presence of concentrated $H_{2}SO_{4}$. Also,compound $X$ gives a precipitate $Y$ when its solution in dilute $HCl$ is treated with $H_{2}S$ gas. The precipitate $Y$ on treatment with concentrated $HNO_{3}$ followed by excess of $NH_{4}OH$ further gives a deep blue coloured solution. Compound $X$ is: