Which of the following sulphates is insoluble in 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?

Which reagent can be used to identify nickel ion $(Ni^{2+})$?

Match List-$I$ with List-$II$:

List-$I$ (Ion)	List-$II$ (Group Number in Cation Analysis)
$A. Co^{2+}$	$I. Group-I$
$B. Mg^{2+}$	$II. Group-III$
$C. Pb^{2+}$	$III. Group-IV$
$D. Al^{3+}$	$IV. Group-VI$

Choose the correct answer from the options given below:

Which of the following ions forms a colored carbonate precipitate?

Which of the following sulfides is completely precipitated upon dilution of its acidic solution?