Question

12c. State one appropriate observation of the following:

A few drops of dilute hydrochloric acid are added to silver nitrate solution followed by the addition of ammonium hydroxide solution.

Answer 1

Step 1: The following observations are made in the given experiment:

1. When a few drops of Dilute Hydrochloric acid HCl are added to Silver nitrate ${\mathrm{AgNO}}_3$ solution, its shows a displacement reaction and forms a clear white precipitate of Silver chloride AgCl along with Nitric acid ${\mathrm{HNO}}_3$ as a by-product.
2. This precipitate formed stays undissolved in the remaining solution of nitric acid.
3. When Ammonium hydroxide solution is added to it, the precipitate is seen to completely dissolve in it.
4. This happens due to the formation of a soluble diamine complex which leaves the solution almost colourless.

Step 2: Chemical reactions involved in the experiment are:

$$\begin{gathered} {\mathrm{AgNO}}_3\left(\mathrm{l}\right)+\mathrm{HCl}\left(\mathrm{aq}\right)\to \mathrm{AgCl}\downarrow +\hspace{0.17em}{\mathrm{HNO}}_3\left(\mathrm{aq}\right) \\ \mathrm{Silver}\mathrm{Hydrochloric}\mathrm{Silver}\mathrm{Nitric} \\ \mathrm{nitrate}\mathrm{Acid}\mathrm{Chloride}\mathrm{Acid} \\ \mathrm{AgCl}\downarrow +{\mathrm{NH}}_4\mathrm{OH}\to \left[\mathrm{Ag}{\left({\mathrm{NH}}_3\right)}_2\right]\mathrm{Cl}+{\mathrm{H}}_2\mathrm{O} \\ \mathrm{Silver}\mathrm{Ammonium}\mathrm{Diamine}\mathrm{Water} \\ \mathrm{Chloride}\mathrm{Hydroxide}\mathrm{Complex} \end{gathered}$$