Question

What do you observes when:
Hydrogen chloride gas is passed through the Silver nitrate solution and the product is thus formed treated with excess Ammonium hydroxide?

Answer 1

Hint: We must know about the double displacement type of reaction for Hydrogen chloride gas and Silver nitrate.


Complete step by step solution:
When Hydrogen chloride gas is passed through a solution of silver nitrate then white precipitate of silver chloride -\[\;AgCl\] can be observed at the bottom of the test tube or vessel.
\[2HCl + 2AgNO3 \to 2AgCl \downarrow + 2HNO3\]
As we can see in the above chemical equation, two products are formed, precipitate of silver nitrate and nitric acid. Silver nitrate still precipitates though nitric acid is formed because silver nitrate is not soluble in nitric acid.but it dissolves readily in excess of ammonium hydroxide solution.
The product formed in above reaction i.e. silver chloride, \[\;AgCl\] when treated with excess of ammonium hydroxide,\[N{H_4}OH\] ,then it results into formation of \[Ag{\left( {N{H_3}} \right)^{2 + }}\] ​ and \[C{l^ - }\] ions.
\[AgCl + 2N{H_4}OH \to Ag{(N{H_3})_2}Cl + {H_2}O\]

Note: We must know that Dilute $HCl$ does not react with nitrates but it only react with silver nitrate that forms a white precipitate of silver chloride. Silver chloride is insoluble in water so why it precipitates. Silver chloride salt is soluble in ammonium hydroxide, only when \[N{H_4}OH\]is present in excess of amount.
 Hydrogen chloride gas reacting Silver nitrate solution is a type of double displacement reaction as the two compounds exchanged their ions . we can use Silver nitrate solution in laboratories to distinguish \[HCl\]from \[HN{O_3}\]because Silver nitrate reacts with hydrochloric acid to form thick curdy white precipitate of silver chloride whereas silver nitrate does not react with nitric acid.