Which of the following ions forms a white precipitate upon the addition of $HCl$ to its aqueous solution?

$A$ laboratory reagent imparts green colour to the flame. On heating with solid $K_2Cr_2O_7$ and conc. $H_2SO_4$,it evolves a red gas. Identify the reagent.

Which reagent is used to distinguish between silver and lead salts?

$Fe^{2+}$ ion can be distinguished from $Fe^{3+}$ ion by

Which one among the following pairs of ions cannot be separated by $H_2S$ in dilute hydrochloric acid?

The pair$(s)$ of ions where $BOTH$ the ions are precipitated upon passing $H_2S$ gas in the presence of dilute $HCl$,is(are):
$(A) Ba^{2+}, Zn^{2+}$
$(B) Bi^{3+}, Fe^{3+}$
$(C) Cu^{2+}, Pb^{2+}$
$(D) Hg^{2+}, Bi^{3+}$