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

$MgSO_4$ on reaction with $NH_4OH$ and $Na_2HPO_4$ forms a white crystalline precipitate. What is its formula?

Compound $A$ on borax bead test in reducing flame gives green colour bead. Compound $A$ on treatment with $H_2O_2$ followed by treatment with $Pb(OAc)_2$ gives yellow ppt. The metal ion in the compound $A$ is :

Assign $A, B, C, D$ from the given type of reaction.
$FeCl_3 + NH_3 \text{ (excess)} \longrightarrow Fe(OH)_3 \downarrow$

Concentrated aqueous $NaOH$ can separate a mixture of

$A$ metal salt gives a yellow precipitate with potassium chromate in acetic acid and a white precipitate with dilute sulfuric acid,but it does not give a precipitate with sodium chloride or sodium iodide. What will be the composition of the white precipitate formed when sodium carbonate is added to the solution of this metal salt?