Question

A mixture of two salts is used to prepare a solution $S$, which gives the following results:
$\text{White precipitate(s) only} \xleftarrow[\text{Room temperature}]{\text{Dilute} NaOH(aq)} \underset{\text{(aq solution of the salts)}}{S} \xrightarrow[\text{Room temperature}]{\text{Dilute } HCl(aq)}$ White precipitate(s) only
The correct option(s) for the salt mixture is(are)

• A. $Pb \left( NO _{3}\right)_{2}$ and $Zn \left( NO _{3}\right)_{2}$
• B. $Pb \left( NO _{3}\right)_{2}$ and $Bi \left( NO _{3}\right)_{3}$
• C. $AgNO _{3}$ and $Bi \left( NO _{3}\right)_{3}$
• D. $Pb \left( NO _{3}\right)_{2}$ and $Hg \left( NO _{3}\right)_{2}$

Answer 1

Answer: (A), (B), (C)

$Pb ( OH )_{2}, Zn ( OH )_{2}$ and $Bi ( OH )_{3}$ are white precipitates but $Hg ( OH )_{2}$ (unstable) is not. $PbCl _{2}$ is white $ppt$.
So, option (A), (B) and (C) are correct.