Question

Which of the following compounds does not give ppt. with dil.HC1?
a.) \[\text{AgN}{{\text{O}}_{\text{3}}}\]
b.) \[\text{Pb}{{\left( \text{N}{{\text{O}}_{\text{3}}} \right)}_{\text{2}}}\]
c.) \[\text{H}{{\text{g}}_{2}}{{(\text{N}{{\text{O}}_{\text{3}}})}_{\text{2}}}\]
d.) \[Cu{{(\text{N}{{\text{O}}_{\text{3}}})}_{\text{2}}}\]

Answer 1

Hint: To answer the correct option, we should do the reaction of each option with dil. HCl We should know about precipitation reactions.


Complete step by step solution:
Let us first understand the precipitation reaction. We should know that a precipitation reaction is about the formation of an insoluble salt. This insoluble salt forms because we do the reaction of two solutions that contain soluble salts. And after this, the insoluble salt that falls out of solution is known as the precipitate. Precipitation reactions can help determine the presence of various ions in solution.
We will react to the dilute HCl with every option to find out which option does not precipitate

\[\text{AgN}{{\text{O}}_{\text{3}}}+H\text{Cl}\to \text{AgCl}+H\text{N}{{\text{O}}_{\text{3}}}\]
In the above reaction, silver nitrate reacts with hydrochloric acid in which solid silver chloride is precipitated out. This is the insoluble salt formed as a product of the precipitation reaction. In the above reaction, a white precipitate called silver chloride or AgCl is formed which is in the solid-state.
\[\text{Pb}{{\left( \text{N}{{\text{O}}_{\text{3}}} \right)}_{\text{2}}}+\text{2HCl}\to ~\text{PbC}{{\text{l}}_{\text{2 }}}+\text{2HN}{{\text{O}}_{3}}\]
In the above reaction, a white precipitate of lead chloride is formed when dilute hydrochloric acid is added to lead nitrate solution at room temperature.
\[\text{H}{{\text{g}}_{2}}{{(\text{N}{{\text{O}}_{\text{3}}})}_{\text{2}}}~+\text{ 2HCl }\to \text{ HgC}{{\text{l}}_{\text{2}}}~+\text{ 2HN}{{\text{O}}_{\text{3}}}\]
We should know that Mercury (II) nitrate reacts with hydrogen chloride to produce mercury (II) chloride nitric acid and hydrogen chloride - diluted solution. This is not a precipitation reaction.
\[\text{Cu}{{\left( \text{N}{{\text{O}}_{\text{3}}} \right)}_{\text{2}}}+\text{HCl}\to \text{CuC}{{\text{l}}_{\text{2}}}+\text{2HN}{{\text{O}}_{\text{3}}}\]
We should know that, when copper nitrate reacts with HCl, an excess of it will produce the green \[{{\left[ \text{CuC}{{\text{l}}_{\text{4}}} \right]}^{\text{2}-}}\]complex. This is a precipitation reaction.

From the above discussion we can say that mercury nitrate present in option C, doesn’t give any precipitate with dilute HCl.


Note: Let us now know about examples of precipitation reaction in our everyday life. We should know that precipitation reactions can be used in wastewater treatment. As we know that in wastewater there is presence of heavy metals such as compounds of sulphide and hydroxide. So, we can add a source of hydroxide that is soluble (NaOH) that will result in a precipitation reaction.