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

Which of the following cations will give a precipitate with $Na_2C_2O_4$ solution in the presence of acetic acid?

Which of the following salts is insoluble in water at room temperature but soluble in boiling water?

If $Pb^{2+}, Cu^{2+}, Al^{3+}, Cd^{2+}, Zn^{2+}$ radicals are present in an aqueous solution,and it reacts with $H^{+}/H_2S$,a precipitate is produced. The solution $(X)$ obtained after the removal of the precipitate is treated with excess $NaOH$. What is the result?

$(Yellow\,ppt)\,T \xleftarrow{{{K_2}Cr{O_4}}} X$ $\xrightarrow{{dil.\,HCl}} Y(Yellow\,ppt) + Z \uparrow (pungent\,smelling\,gas)$. If $X$ gives green flame test,then $X$ is:

Aqueous solution of $FeSO_4$ does not produce a precipitate with: